Introduction
Goats are an increasingly popular pet animal in the US. Pet goats are often managed differently and reach an older age compared to goats used as production animals. Owners of pet goats are often willing to invest more resources in diagnosis and treatment of chronic or complex disease conditions such as neoplasia. However, unlike in small-animal or equine medicine in which neoplastic diseases are better understood, there are limited published data on clinical presentation, treatment, or outcome in goats with neoplasia.
Specific caprine neoplasms have been described in case reports and a limited number of retrospective analyses.1–6 Yau and Rissi7 reported a case of a goat with cholecystic adenocarcinoma and insulinomas, and 2 cases of leiomyosarcoma in related Saanen does have been described. Hill et al6 reported the clinical signs, signalment, treatment, and outcomes of 13 cases of goats diagnosed with thymomas over a 24-year period. While that study6 was useful in describing clinical signs associated with thymomas, it was limited to 1 type of thoracic neoplasia and had a limited number of animals. Furthermore, clinical signs and outcomes of other neoplasms such as mammary gland carcinomas have only been reported in case reports involving a single animal.3,8,9 A 25-year retrospective analyzed goat neoplasia on the basis of biopsy or necropsy submissions to a veterinary diagnostic lab.10 That study10 summarized types of neoplasm in different breeds of goats, but because it was based on necropsy data, it did not include information on the antemortem clinical aspects of neoplasia in goats. Further investigation needs to be done to confirm, compare, and widen the findings of these papers as well as to expand the number of cases available in the literature to strengthen confidence in clinical presentations, treatments, and outcomes of neoplastic processes.
While some neoplasia can be diagnosed using routine testing common to most veterinary practices, goats that have unusual clinical signs, failed to respond to treatment, or have an advanced disease process are often referred to veterinary teaching hospitals for advanced diagnostics and treatment. While some diagnostic and treatment techniques can be extrapolated from other species, the clinical manifestation and response to treatment of goats with neoplasia remain largely undetermined. The objectives of this retrospective study were to identify goats definitively diagnosed with neoplasia at a veterinary teaching hospital over a 15-year period and describe their presenting complaint, diagnostic testing, treatment, and short- and long-term outcomes. The results of this study can help increase awareness of neoplasia in the expanding pet goat population and provide veterinarians with information to help guide clinical decision-making in goats diagnosed with neoplasia.
Materials and Methods
The medical record databases at the Colorado State University Veterinary Teaching Hospital were systematically reviewed to identify goats admitted to the hospital between March 2007 and March 2022 that were definitively diagnosed with neoplasia. Definitive diagnosis was made by antemortem (fine-needle aspirate [FNA] or biopsy) or postmortem (tissues collected during a necropsy) sample collection and cytologic or histopathologic evaluation by a board-certified American College of Veterinary Pathologists clinical or anatomic pathologist. Goats submitted directly to the Veterinary Diagnostic Laboratory for necropsy without a clinical evaluation were excluded. Goats evaluated by the teaching hospital antemortem and all neoplasms, including those considered incidental, were reported. The medical record for each goat was reviewed, and the following items were extracted: signalment, presenting complaint, breeding history (for does), duration of clinical signs, testing that resulted in a neoplasia diagnosis, evidence of metastasis, treatment, and short-term outcome. Short-term outcome was defined as survival to discharge. Long-term outcome was obtained by contacting owners via email or phone.
Statistical analysis
The average and median of age, duration of clinical signs, and outcomes were calculated. Comparison between select categorical variables was performed with a χ2 analysis or Fisher exact test using Prism version 9.5.0 (GraphPad Software), and P values are reported. A P value < .05 was considered to be statistically significant.
Results
A total of 1,441 goats were evaluated at the Colorado State University Veterinary Teaching Hospital during the study period. Forty-six goats were definitively diagnosed with 58 neoplasms via histopathology or cytologic evaluation of FNA samples, making the prevalence of neoplasia within the caprine patient population 3.2%. Eleven goats had 2 distinct tumor types and 1 goat had 3. The median age at the time of diagnosis was 8 years (range, 3 to 17 years). Sex distribution was 38 female (83%), 7 castrated male (15%), and 1 spayed female (2%). The most commonly represented breeds were Nubian (n = 10), Saanen (7), and Pygmy (6). Other breeds included Nigerian Dwarf (n = 3), Alpine (3), Cashmere (2), Angora (2), La Mancha (1), Boer (1), Oberhasli (1), Tennessee Fainting (1), and mixed breed or unknown breed (9). When compared to the total population of goats admitted to the Veterinary Teaching Hospital during the study period, the Saanen breed was overrepresented (P < .0001) but the Nubian breed was not (P = .12). Medical imaging modalities used for tumor identification or metastasis evaluation or both included radiography and ultrasonography. Computed tomography was performed in 3 goats. Evidence for metastases was most commonly sought by performing thoracic radiographs or finding metastatic lesions on postmortem examination.
Clinical signs, duration of clinical signs prior to presentation, and tumor location are summarized (Table 1). The most commonly identified neoplasms were squamous cell carcinoma (SCC) followed by thymoma and mammary carcinoma.
Summary of goats presented to a veterinary teaching hospital with a confirmed neoplastic process based on location of the tumor, associated clinical signs, and duration of clinical signs prior to presentation.
Location | Clinical signs | Median | Range |
---|---|---|---|
Skin | Visible mass (11) | 4 mo | 0.5–12 mo |
Hyporexia (1) | N/A | N/A | |
Teat enlargement (1) | 2 y | 2 y | |
Thoracic | Visible mass (7) | 2 mo | 0.3–12 mo |
Hyporexia (3) | 4.5 wk | 0.5–12 wk | |
Respiratory (2) | 14 mo | 4–24 mo | |
Mammary | UE (9) | 5 mo | 0.5–240 mo |
Weight loss (2) | 2 mo | 1–3 mo | |
Recurrent mastitis (2) | 3 y | 2–4 y | |
Udder necrosis (1) | N/A | N/A | |
Uterine | HVD (5) | 26 wk | 2–96 wk |
UE (2) | 1 y | 1–2 y | |
Bloat (1) | 5 h | 5 h | |
Seizures (1) | 3 h | 3 h | |
Pituitary | UE (3) | 1 y | 1–2 y |
HVD (2) | 3 wk | 2–4 wk |
Tumor types are grouped by mass location and clinical observation. The number in parentheses next to the clinical signs indicates the number of animals that were presented for that clinical sign. A single animal could have been presented for multiple clinical signs.
HVD = Hemorrhagic vaginal discharge. UE = Udder enlargement.
Skin neoplasia
Thirteen (28%) goats with a median age of 7 years (range, 3 to 15 years) had at least 1 skin mass diagnosed as SCC. Four of the 13 (31%) goats diagnosed with skin SCC were Saanens, though Saanens were not overrepresented in this group (P = .20). Other breeds included Cashmere (n = 3), mixed breed (2), Nubian (1), Nigerian Dwarf (1), Boer (1), and Tennessee Fainting (1). The majority of goats with SCC (12/14 [86%]) had a white hair coat. Squamous cell carcinoma of the skin was most commonly identified on the udder (6/14 [43%]) and perianal region (5/14 [36%]). One goat had masses on both the udder and perianal regions. Other anatomic locations for SCC included vagina (n = 1), nose (1), and maxilla (1). One of the goats with SCC of the perianal region was a spayed female. Treatments, along with short- and long-term outcomes for the goats diagnosed with SCC are compiled (Table 2). Twelve goats also had long-term outcomes available. Management of these cases included surgical excision only, cryotherapy and surgical excision, and monotherapy with meloxicam or piroxicam. Immunohistochemistry was not performed to determine whether the SCCs were cyclooxygenase-2 positive prior to treatment with meloxicam or piroxicam. Of the 14 animals diagnosed with SCC, 5 had incisional biopsies performed prior to mass removal, 5 had excisional biopsies performed, 1 had an FNA performed followed by histopathology on the surgically removed tissue, and 1 was definitively diagnosed via histopathology on postmortem.
Cases of squamous cell carcinoma in 14 goats presented to a veterinary teaching hospital described by tumor location, treatment type, and short- and long-term outcomes. Where available, the time frame for long-term outcome is defined in parentheses.
Tumor location | Treatment | Short-term outcome | Long-term outcome |
---|---|---|---|
Udder | SX | Discharged | N/A |
Discharged | +** | ||
Bilateral mastectomy | Discharged | - (6 y) | |
Discharged | - (6 y) | ||
SX and cryo | Discharged | - (9 mo) | |
Discharged* | + (5 mo)** | ||
Perianal | SX | Discharged | - *** |
Discharged | N/A | ||
SX and cryo | Discharged* | + (5 mo)** | |
SX and rad | Discharged | + | |
Medical (Meloxicam) | Discharged | ++ | |
Nasal | NT | Discharged | ++ |
Maxillary | Medical (Piroxicam) | Discharged | ++ |
Esophageal | NT | Euthanized | N/A |
Vaginal | NT | Euthanized | N/A |
Cryo = Cryotherapy. NT = No treatment. Rad = Radiation Therapy. SX = Surgical mass excision.
*Same goat with 2 tumor locations. **Further treatment with cryotherapy initiated. ***No regrowth at euthanasia, however date of euthanasia unknown. +Regrowth. -No regrowth. ++Continued growth.
Thoracic neoplasia
Thoracic masses were diagnosed in 13 of 46 (28%) goats. Breeds in this group included Pygmy (n = 4), Nubian (3), mixed breed (3), Saanen (1), Oberhasli (1), and Alpine (1). Of these, 9 of 13 (69%) were identified as thymomas. Other thoracic masses included hemangiosarcoma (n = 1), lymphoma (1), pulmonary adenocarcinoma (1), and carcinoma (1). Of the thymomas, 4 were cranial mediastinal, 4 were ventral cervical, and 1 goat had a thymoma in both locations. Of the cranial mediastinal thymomas, 3 of 4 (75%) were considered incidental findings identified at necropsy; 1 goat was euthanized for declining health attributed to severe nephroliths and pyelonephritis, 1 goat was euthanized for a progressive forelimb lameness, and 1 goat was euthanized intraoperatively due to a nonresectable leiomyofibroma of the uterus. In the latter 2 animals, incidental mediastinal masses were noted on thoracic radiographs prior to euthanasia but a definitive diagnosis was not made until necropsy. In 6 of 9 goats diagnosed with thymoma, FNA was the first diagnostic procedure attempted to diagnose the mass. Out of these, FNA was nondiagnostic in 3 of 6 (50%). Two FNAs were suggestive of lymphoma or thymoma and the third report was suggestive of a lymphosarcoma, but none could be differentiated on FNA alone. In these cases, biopsy was recommended and ultimately histopathology was pursued for a definitive diagnosis.
Treatments and short- and long-term outcomes were available for 8 of 9 goats diagnosed with a thymoma. One goat had an intermittent exercise-induced cough associated with the cranial mediastinal thymoma, and a surgical median sternotomy was attempted. The patient died during recovery due to cardiac arrest. The remaining 4 goats with cranial mediastinal thymomas and the 1 goat with both ventral cervical and cranial mediastinal thymomas were euthanized without treatment. Of the goats with ventral cervical thymomas, 3 of 4 underwent surgical mass removal with no complications and all survived to discharge. One experienced mass regrowth in the same location 1.5 years postoperatively. This regrowth was suspected to be a thymoma, but it was not definitively rediagnosed. One goat was euthanized 1 year postoperatively for unrelated causes with no evidence of mass regrowth. Long-term follow-up could not be obtained for the third goat treated surgically. The goat that did not undergo surgical resection of its ventral cervical thymoma was discharged with prednisolone for palliative care. This goat died 2 years postdiagnosis for unknown causes with head pressing observed by the owner prior to death.
Mammary neoplasia
Ten of 46 (22%) goats were diagnosed with 11 mammary neoplasms. The median age at diagnosis was 8 years (range, 3.5 to 12 years). There was a trend toward significance for the Nubian breed being overrepresented (5/10; P = .07). Other breeds included Alpine (n = 2), Saanen (1), Angora (1), and mixed breed (1). Common clinical presentations and duration of clinical signs prior to presentation are summarized (Table 1).
The most frequent presenting complaint in this group was udder enlargement, which was present in 9 of 10 (90%) goats. Three of these does had kidded at least once, 4 had never been bred, and 3 had unknown breeding histories. The median duration of udder enlargement prior to evaluation was 5 months (range, 0.5 to 240 months). Other clinical signs included recurrent mastitis (n = 2), weight loss (2), and udder necrosis (1). The most commonly identified mammary neoplasm was adenocarcinoma, identified in 6 of 11 (55%) goats, followed by adenoma in 3 of 11 (27%), myoepithelioma in 1 of 11 (9%), and a sarcoma in 1 of 11 (9%) goats. Eight of the goats with mammary neoplasia underwent treatment with a bilateral mastectomy. Surgery was not elected in the remaining 2 goats due to poor overall condition and high risk of surgical and anesthetic complications. In these 2 cases, euthanasia was elected. All 8 of the goats that underwent surgical mastectomy survived to discharge, and long-term follow-up was available for 5. Three of the 5 were euthanized for unrelated causes 5 to 34 months postoperatively. Necropsies performed on all 3 showed no evidence of metastasis; however, 1 goat had a leiomyolipoma of the pylorus. Each of the other 2 goats were still alive and had no evidence of mass regrowth at the time of their follow-up 24 and 21 months postoperatively.
Uterine neoplasia
Six goats (6/46 [13%]) in the study were diagnosed with uterine neoplasia. The median age at time of diagnosis was 7.25 years (range, 4 to 10 years). Of these, 3 (3/6 [50%]) goats were of the Pygmy breed and the Pygmy breed was overrepresented (P = .02). Other breeds included Nigerian Dwarf (n = 1), Cashmere (1), and mixed breed (1). Common clinical presentations and duration of clinical signs prior to presentation are summarized (Table 1). Uterine neoplasia can be difficult to diagnose via ultrasonography, as often these heterogeneous masses are hard to trace back to a likely irregular uterus (Figure 1). Four of the uterine neoplasms were leiomyosarcoma (4/6 [67%]) with the remaining neoplasms identified as leiomyofibroma (1/6 [17%]) and mural round cell tumor (1/6 [17%]). Four goats also had 1 other distinct neoplasm identified at necropsy including 2 pituitary adenomas, a cranial mediastinal thymoma, and an adenocarcinoma of the liver. Ovariohysterectomy was performed in 3 of 6 (50%) of the goats. All 3 were euthanized intraoperatively because the uterine mass was deemed nonresectable. Medical management with 3 prostaglandin trials (dinoprost tromethamine; 2.5 to 5 mg, IM, q 12 to 24 h for 1 to 3 days) and prednisone (tapering course over 4 weeks with starting dose of 0.45 mg/kg, PO, q 24 h followed by maintenance dosage of 0.2 mg/kg, PO, q 24 h for 6 months) was attempted in 1 goat. This animal was treated for 14 months but was eventually euthanized 2 years after diagnosis due to worsening clinical signs. Humane euthanasia without attempted treatment was elected in 2 of 6 animals due to poor condition of the animal.

Ultrasonographic image of a heterogenous soft tissue mass (arrows) with a pocket of anechoic fluid (arrowheads) in the caudal abdomen of a doe, bordered cranially by peritoneal fluid (asterisk).
Citation: Journal of the American Veterinary Medical Association 261, 5; 10.2460/javma.22.11.0530

Ultrasonographic image of a heterogenous soft tissue mass (arrows) with a pocket of anechoic fluid (arrowheads) in the caudal abdomen of a doe, bordered cranially by peritoneal fluid (asterisk).
Citation: Journal of the American Veterinary Medical Association 261, 5; 10.2460/javma.22.11.0530
Ultrasonographic image of a heterogenous soft tissue mass (arrows) with a pocket of anechoic fluid (arrowheads) in the caudal abdomen of a doe, bordered cranially by peritoneal fluid (asterisk).
Citation: Journal of the American Veterinary Medical Association 261, 5; 10.2460/javma.22.11.0530
Pituitary neoplasia
Three goats were diagnosed with pituitary neoplasia. Two animals were Nigerian Dwarfs, and 1 was a mixed breed. All 3 had udder enlargement and a second distinct tumor type. These secondary tumors included uterine leiomyosarcoma, uterine sarcoma, and c-cell thyroid adenoma. Common clinical presentations and duration of clinical signs prior to presentation are summarized (Table 1).
Uncategorized neoplasia
The remainder of the neoplasms as well as location, signalment, tumor type, presenting complaint, and duration of complaint are summarized (Table 3). Three goats were diagnosed with hepatic neoplasia that included melanoma, adenocarcinoma, and biliary carcinoma.
Uncategorized tumors in 10 goats described by anatomic location, signalment, presenting complaint, and duration of complaint as a part of a retrospective descriptive study examining types, clinical features, and outcomes of caprine neoplasia cases seen at a veterinary teaching hospital.
Location | Signalment | Tumor type | Presenting complaint | Duration |
---|---|---|---|---|
Liver | 7 y Angora doe | Melanoma | Lethargy | 1 d |
17 y MB wether | Biliary carcinoma | Mass at thoracic inlet* | N/A | |
11 y Pygmy doe | Adenocarcinoma | Hemorrhagic vaginal discharge* | N/A | |
Urinary bladder | 17 y MB wether | LMS | Mass at thoracic inlet* | N/A |
8 y Cashmere doe | Leiomyoma | Seizure like activity | 3 h | |
Ataxia (progressive) | 3 mo | |||
Mandible | 4 y La Mancha wether | PGCG | Mandibular mass | 2 wk |
Dark teeth | 2 wk | |||
Nasal | 11 y Nubian doe | TCC | Nostril mass | 9 d |
Pylorus | 5 y Angora doe | Leiomyolipoma | Bloat | 1 wk |
Thyroid | 4 y ND doe | C-cell adenoma | Udder enlargement | N/A |
Adrenal | 11 y Saanen doe | Pheochromocytoma | Weight loss | 1 y |
Lethargy | 3 d | |||
Esophagus | 13 y Saanen doe | SCC | Bloat | 1 mo |
Hyporexia | 2 wk |
LMS = Leiomyosarcoma. MB = Mixed breed. ND = Nigerian Dwarf. PGCG = Peripheral giant cell granuloma. SCC = Squamous cell carcinoma. TCC = Transitional cell carcinoma.
*Presenting complaint considered unrelated to the diagnosed neoplasm.
Two goats were diagnosed with neoplasia of the urinary bladder including 1 leiomyosarcoma and 1 leiomyoma, both of which were considered incidental findings on necropsy. One of these goats was euthanized for acute seizure activity, and the other was euthanized due to a hemangiosarcoma at the thoracic inlet. Neither of these goats had uterine involvement.
The remaining neoplasms identified in goats during the study period included a peripheral giant cell granuloma of the mandible, nasal transitional cell carcinoma, leiomyolipoma of the pylorus, c-cell adenoma of the thyroid, pheochromocytoma of the adrenal gland, and an SCC of the esophagus.
Discussion
The present study identified several interesting clinical aspects of neoplasia in a primarily pet goat population. One notable finding was the low prevalence of neoplasia (3.2%) within the goat study population. In contrast, a previous investigation10 found a higher prevalence of 8.7% in samples submitted to a diagnostic lab for necropsy or histopathology. The present study looked at confirmed cases of neoplasia in goats that presented for clinical evaluation at a veterinary teaching hospital. The lower prevalence of 3.2% was surprising because Colorado State University sees a primarily older pet goat population and serves as a referral center for unusual or challenging cases. Both features would seem likely to increase the number of goats with neoplasia within the patient population. Unfortunately, there are limited data reporting the prevalence of neoplasia in goats in other patient populations, making it difficult to surmise whether neoplasia is underdiagnosed in clinical settings or, more specifically, in pet goats.
Many of the goats in the present study were kept as pets rather than production animals. Pet goats often have a longer life-span and owners who are not constrained by the need for their goat to be economically productive. Neoplasms that affect fertility, weight gain, and lactation may be diagnosed sooner when the animal’s productivity is more closely monitored in a production setting. For example, goats with infertility due to uterine neoplasia would likely be recognized sooner in a production setting than in a pet goat that is not regularly bred. However, goats in production settings that become ill or show an unexplained drop in production are more likely to be culled from the herd without pursuing a diagnosis.
One large-scale investigation10 of neoplasia in goats found some similarities with the present study. One similarity was the age of affected goats with a median age of 8 in the present study compared to the previously reported 7 years. This finding was not surprising because neoplasia is generally uncommon in young animals. Another notable similarity was identifying Saanens and Nubians as the most commonly affected breeds. This was particularly noteworthy in the present study in which Saanen goats were not the most common breed in the general goat patient population. Saanens living in Colorado with their light pigmentation are likely at higher risk than other darker pigmented breeds for developing SCC. Nubian does made up half of the mammary tumor group in the present study, which was similar to the 3 of 7 observed by Löhr10 when describing does with mammary carcinomas. A case report3 of a mammary adenocarcinoma has also been described in a Nubian buck. Of the 10 does with mammary tumors in the present study, 3 had kidded at least once, 4 had never been bred, and 3 had unknown breeding histories. Further studies may be warranted to investigate a correlation between milking breeds as well as the significance of lactation status on mammary tumors.
A large portion (14/58 [24%]) of neoplasms in the present study were SCC, but the prevalence of SCC within the goat study population was similar to what has been reported in sheep11 and goats.12 One of the few reports looking at the prevalence of SCC in goats published a prevalence of 5.8% and 0.75% on 2 separate Brazilian farms.12 Another study investigating SCC in Australian farmed sheep found a prevalence of 0.12% to 4%.11 The prevalence of SCC in the present study, which evaluated patients that were presented to a teaching hospital, was similar to these findings at 1% (14/1,441). This suggests that SCC is a common type of neoplasm in goats but not a commonly diagnosed condition. This discrepancy is likely to be true for other neoplasms as well. It is possible that SCC in goats is even less common in other geographic locations. The high elevation around Fort Collins, Colorado (1,519 m), with greater radiation exposure likely increases the risk of SCC, especially in lightly pigmented animals like Saanens. Lack of skin pigmentation and high UV light exposure have been shown to be predisposing factors for the development of SCC due to increased cellular mutations.13 Therefore, not unexpectedly, 87% of goats with SCC had white hair coats. Additionally, goats with SCC are often treated initially by local veterinarians and only referred if lesions are more advanced. Because the Colorado State University livestock clinic serves as both a referral and primary care facility, it is possible that goats with SCC are seen for both initial diagnosis and treatment as well as in cases of advanced disease or poor response to prior therapy.
Treatments for goats with SCCs are presented (Table 2). The majority of goats had surgical excisions performed, a few with adjunctive cryotherapy (1 to 2 sessions/goat) or radiation therapy (intraoperative brachytherapy; n = 1). Lesion size was not consistently available in the medical records. In 1 study4 of SCC in goats, lesion resolution was hypothesized to be more closely related to size of the initial mass as opposed to treatment performed, emphasizing the importance of early treatment to achieve remission. Medical management of SCC was attempted in 2 goats. One was treated with meloxicam (1.25 mg/kg, PO, q 24 h) and the other with piroxicam (0.3 mg/kg, PO, q 24 h). Neither of these resulted in mass resolution. The goat treated with meloxicam was euthanized 3 weeks after initiation of medical management for a suspected acute kidney injury diagnosed on necropsy. The goat treated with piroxicam was euthanized at an unknown time following initial treatment for continued mass growth. Research has shown that piroxicam may be useful in the treatment of oral SCC in dogs14; however, to the authors’ knowledge, there have been no studies to date evaluating the efficacy of piroxicam for treatment of SCC in livestock species. Further studies on caprine SCC investigating lesion size and response to treatment are needed.
Udder enlargement was the main clinical sign in goats with mammary neoplasia and goats diagnosed with pituitary tumors. In humans with pituitary tumors, prolactin produced by the anterior pituitary gland is often upregulated, leading to galactorrhea.15 It is possible that a similar process occurs in goats, making pituitary neoplasia an important differential diagnosis for goats with unexplained udder enlargement. Udder enlargement was also a key clinical finding in goats with mammary neoplasia with a wide range from 0.5 to 240 months. Of the 10 goats in the mammary neoplasia group, 5 had a history of treatment for suspected mastitis at 1 point prior to admission to the veterinary teaching hospital. This data demonstrates the need for milk cultures to definitively diagnose mastitis as well as the need for further diagnostics in the event of a negative culture or unresponsive treatment. Neoplasia should be considered a differential in goats with udder enlargement.
Within the group of goats diagnosed with thoracic neoplasia, the most common neoplasm was a thymoma. The majority (3/4 [75%]) of mediastinal thymoma neoplasms were considered incidental findings as they did not have associated clinical signs and were found coincidentally on radiographs or necropsy. Reported clinical signs associated with mediastinal thymomas appear to be variable as one report6 found that goats with mediastinal masses displayed evidence of respiratory distress or marked tachypnea while another2 reported that no clinical signs could be attributed to thymomas in dairy goats. Neoplasms that are found incidentally or do not appear to negatively affect a goat’s health may go undiagnosed due to the risk and cost of pursuing invasive diagnostics. As a result, the incidence of mediastinal thymomas may be higher than what was reported in the present study. In contrast, goats with ventral cervical thymomas presented most commonly for a visible mass. The majority of these goats underwent surgical excision without complications. Resecting these masses is important because clinical signs associated with compression of adjacent structures include respiratory signs or megaesophagus.16 Resection of suspected ventral cervical thymomas prior to definitive diagnosis may be an appropriate treatment in some cases because diagnosis with minimally invasive techniques like FNA can be challenging.17 In 6 of 9 of the goats diagnosed with thymomas, the initial attempt at mass diagnosis was FNA and cytology. Of these 6 goats, FNA was nondiagnostic in 3 (50%). The large number of proliferating lymphoid cells in thymomas make diagnosis by FNA challenging. The small number of cells evaluated by cytology is often insufficient to definitively differentiate a thymoma from other structures or masses, such as lymph nodes and lymphoma. Biopsy for histopathology, while more invasive and costly, could increase the likelihood of obtaining a diagnosis in goats with suspected thymoma.
The overall prevalence of metastasis in the present study population was low (4/58 [7%]). The tumors with confirmed metastasis were mammary sarcoma with metastasis to the lungs, mediastinal carcinoma with metastasis to the lungs and mesentery, hepatic melanoma with metastasis to the spleen and kidney, and hepatic adenocarcinoma with metastasis to the lungs and mesenteric lymph nodes. In contrast to other species such as dogs18 and humans,19 there was no evidence of metastasis in any of the goats diagnosed with mammary carcinoma. Follow-up data were available for 5 of 8 goats that underwent surgical mastectomy for known or suspected mammary neoplasia. None of the goats that underwent mastectomy showed evidence of metastasis or regrowth on follow-up (range, 5 months to 4 years), suggesting that complete mastectomy may be curative if no metastasis is present at the time of surgery. Surgical mastectomy with small, noninvasive tumors is known to be an effective treatment in dogs.20 Mastectomy should be considered as a treatment option for pet goats with mammary neoplasia in which raising kids and producing milk are less important to owners than longevity and quality of life. It should be noted, however, that not all goats in the present study had additional diagnostics performed to evaluate for metastasis, diagnostics performed were mainly limited to thoracic radiographs, and metastasis may have occurred in goats after initial tumor diagnosis. Thus, the rate of metastasis may be higher than what was reported in the present study.
In the US, goats are legally considered a food-animal species regardless of their intended purpose (pet vs production animal). Therefore, any extralabel drug use in goats must satisfy the requirements for such use under the AMDUCA of 1994. Many medications (eg, piroxicam) that were identified in the medical records as having been given to goats in this study were not FDA approved for use in goats. In these cases, an official request should have been submitted to the Food Animal Residue Avoidance Databank for determination of an appropriate withdrawal interval. Due to the limited number of drugs approved for use in goats, responsible and legal extralabel drug use is therefore likely to continue to constitute an important means of treating goats with a wide range of diseases, including neoplastic conditions. There is no clear guidance regarding the use of radiation therapy under AMDUCA. Use of traditional chemotherapeutic agents was not identified in the medical records of the goats in the present study. Under the tenets of AMDUCA, a veterinarian must be able to ensure that administration of the drug to a food animal would not pose a public health risk and furthermore that a suitable withdrawal period can be established. Lack of data regarding legal, safe, and efficacious use of chemotherapeutics in goats is a major hurdle to incorporating these drugs into clinical practice. Laws regarding use of extralabel drugs, chemotherapeutics, and radiation therapy may differ in other countries.
The primary limitations of this study were the retrospective nature and small number of goats diagnosed with each type of neoplasia. Drawing conclusions about treatment and progress must be done with caution. Further studies are needed to prospectively investigate treatment and outcome in goats with neoplasia and identify risk factors to improve early diagnosis. In the mean time, it is important to emphasize to pet-goat owners the importance of early evaluation and close monitoring for clinical signs that could indicate neoplasia.
Acknowledgments
No third-party funding or support was received in connection with this study or the writing or publication of this manuscript. The authors declare that there were no conflicts of interest.
The authors thank Elizabeth Heiney for their assistance in data collection.
References
- 1.↑
Yau W, Rissi DR. Cholecystic adenocarcinoma and pancreatic insulinomas in a goat. J Vet Diagn Invest. 2014;26(6):827–831. doi:10.1177/1040638714553294
- 2.↑
Hadlow WJ. High prevalence of thymoma in the dairy goat. Report of seventeen cases. Vet Pathol. 1978;15(2):153–169. doi:10.1177/030098587801500202
- 3.↑
Wooldridge AA, Gill MS, Lemarchand T, Eilts B, Taylor HW, Otterson T. Gynecomastia and mammary gland adenocarcinoma in a Nubian buck. Can Vet J. 1999;40(9):663–665.
- 4.↑
Gibbons PM, Lamb L, Mansell J. Presentation, treatment, and outcome of squamous cell carcinoma in the perineal region of 9 goats. Can Vet J. 2015;56(10):1043–1047.
- 5.
Linton JK, Heller MC, Bender SJ, Stefanovski D, Fecteau ME. Neoplasia of the tubular genital tract in 42 goats. J Am Vet Med Assoc. 2020;256(7):808–813. doi:10.2460/javma.256.7.808
- 6.↑
Hill JA, Fubini SL, Hackett RP. Clinical features, treatment, and outcome in goats with thymomas: 13 cases (1990-2014). J Am Vet Med Assoc. 2017;251(7):829–834. doi:10.2460/javma.251.7.829
- 7.↑
Whitney KM, Valentine BA, Schlafer DH. Caprine genital leiomyosarcoma. Vet Pathol. 2000;37(1):89–94. doi:10.1354/vp.37-1-89
- 8.↑
Quintas H, Alegria N, Mendonça A, Botelho A, Alves A, Pires I. Coexistence of tuberculosis and mammary carcinoma in a goat. Reprod Domest Anim. 2014;49(4):606–610. doi:10.1111/rda.12332
- 9.↑
Cooke MM, Merrall M. Mammary adenocarcinoma and granulosa cell tumour in an aged Toggenberg goat. N Z Vet J. 1992;40(1):31–33. doi:10.1080/00480169.1992.35695
- 10.↑
Löhr CV. One hundred two tumors in 100 goats (1987-2011). Vet Pathol. 2013;50(4):668–675. doi:10.1177/0300985812471544
- 11.↑
Hawkins CD, Swan RA, Chapman HM. The epidemiology of squamous cell carcinoma of the perineal region of sheep. Aust Vet J. 1981;57(10):455–457. doi:10.1111/j.1751-0813.1981.tb05764.x
- 12.↑
Barbosa JD, Duarte MD, Oliveira CMC, et al. Carcinoma de células escamosas perineal em cabras no Pará. Pesqui Vet Bras. 2009;29(5):421–427. doi:10.1590/S0100-736X2009000500011
- 13.↑
Méndez A, Pérez J, Ruiz-Villamor E, García R, Martín MP, Mozos E. Clinicopathological study of an outbreak of squamous cell carcinoma in sheep. Vet Rec. 1997;141(23):597–600. doi:10.1136/vr.141.23.597
- 14.↑
Schmidt BR, Glickman NW, DeNicola DB, de Gortari AE, Knapp DW. Evaluation of piroxicam for the treatment of oral squamous cell carcinoma in dogs. J Am Vet Med Assoc. 2001;218(11):1783–1786. doi:10.2460/javma.2001.218.1783
- 15.↑
Malarkey WB. Prolactin and the diagnosis of pituitary tumors. Annu Rev Med. 1979;30(1):249–258. doi:10.1146/annurev.me.30.020179.001341
- 16.↑
Parish SM, Middleton JR, Baldwin TJ. Clinical megaoesophagus in a goat with thymoma. Vet Rec. 1996;139(4):94. doi:10.1136/vr.139.4.94
- 17.↑
Willner J, Zhou F, Moreira AL. Diagnostic challenges in the cytology of thymic epithelial neoplasms. Cancers (Basel). 2022;14(8):2013. doi:10.3390/cancers14082013.
- 18.↑
Pérez Alenza MD, Tabanera E, Peña L. Inflammatory mammary carcinoma in dogs: 33 cases (1995-1999). J Am Vet Med Assoc. 2001;219(8):1110–1114. doi:10.2460/javma.2001.219.1110
- 19.↑
Welch DR, Steeg PS, Rinker-Schaeffer CW. Molecular biology of breast cancer metastasis. Genetic regulation of human breast carcinoma metastasis. Breast Cancer Res. 2000;2(6):408–416.
- 20.↑
Sorenmo KU, Shofer FS, Goldschmidt MH. Effect of spaying and timing of spaying on survival of dogs with mammary carcinoma. J Vet Intern Med. 2000;14(3):266–270. doi:10.1892/0891-6640(2000)014<0266:eosato>2.3.co;2