Bilateral nasal discharge, respiratory noise, and decreased feed intake in a 19-year-old American Quarter Horse mare

Anna K. Tomlinson Department of Population and Production Medicine, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS

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Robin L. Fontenot Department of Population and Production Medicine, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS

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Marc A. Seitz Department of Clinical Sciences, College of Veterinary Medicine, Mississippi State University, Mississippi State, MS

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History

A 19-year-old 509-kg American Quarter Horse mare was referred for a 2-week history of bilateral nasal discharge, respiratory noise, and decreased feed intake. The referring veterinarian performed an upper airway endoscopy, which revealed masses and serosanguinous material in the left guttural pouch.

On physical examination, the patient had moderate respiratory stridor and mild dyspnea. There was a moderate amount of malodorous, serosanguinous nasal discharge coming from the left nostril, and crusting around the right nostril. No clinically significant abnormalities were seen on a CBC and serum chemistry. Radiographs of the skull were performed (Figure 1).

Figure 1
Figure 1
Figure 1

Radiographic images (left lateral [A] and dorsoventral [B]) of the guttural pouch region of a 19-year-old 509-kg American Quarter Horse mare evaluated for a 2-week history of bilateral nasal discharge, respiratory noise, and decreased feed intake.

Citation: Journal of the American Veterinary Medical Association 261, 3; 10.2460/javma.22.11.0514

Format differential diagnoses, then continue reading.

Diagnostic Imaging Findings and Interpretation

Two-view radiographs of the skull revealed a smoothly marginated, ovoid, soft tissue opaque mass within the ventral aspect of the left guttural pouch that measured approximately 13 X 6 cm and contained stippled gas throughout. The mass was causing ventral deviation of the guttural pouch, resulting in severe dorsoventral narrowing of the nasopharynx. The adjacent nasopharyngeal and laryngeal soft tissues were moderately thickened, and mild, smoothly marginated periosteal proliferation was present along the medial aspect of the left stylohyoid bone. The paranasal sinuses and nasal cavity that were visible were normal (Figure 2).

Figure 2
Figure 2
Figure 2

Same images as in Figure 1. A—There is a smoothly marginated, ovoid, soft tissue opaque mass (dashed line) within the ventral aspect of the left guttural pouch that contains stippled gas throughout. The mass is causing ventral displacement of the guttural pouch with resultant severe narrowing of the nasopharynx (white arrow). B—There is mild, smoothly marginated periosteal proliferation along the medial aspect of the left stylohyoid bone (black arrow). On the dorsoventral projection, the mass is seen as an ill-defined increase in soft tissue opacity superimposed over the left guttural pouch region, left of midline.

Citation: Journal of the American Veterinary Medical Association 261, 3; 10.2460/javma.22.11.0514

On the basis of these findings, the differential diagnoses included fungal etiologies, abscess, and neoplasia. An upper airway endoscopy was performed and revealed a nodular-like mass along the floor of the left guttural pouch with surrounding necrotic tissue, a smooth epithelium-covered swelling off the base of the stylohyoid bone in the right guttural pouch, and edema of the arytenoids, epiglottis, soft palate, and esophagus. Cytology and histopathology of samples taken during the endoscopy were nondiagnostic. Computed tomography was recommended for further evaluation of the extent of the mass and possible surgical planning to obtain biopsies.

The patient was placed under general anesthesia and scanned in dorsal recumbency with a 16-slice CT scanner in the transverse plane with the following settings: 120 kVp, 50 mA, 7,400-millisecond exposure time, 2-cm slice thickness, 512 X 512 matrix, and an 18-cm field of view. Sagittal and dorsal reconstructions were available for review as well. Within the ventral aspect of the left guttural pouch, a soft tissue–attenuating, smoothly marginated, and irregularly shaped mass was present, measuring 12.4 X 5.8 X 7.1 cm, and it had numerous gas bubbles throughout its parenchyma. The mass was causing rightward deviation and ventral compression of the nasopharynx and laryngopharynx as well as a rightward midline shift of the soft tissue between the guttural pouches. Additionally, within the right sphenopalatine sinus, there was a soft tissue–attenuating, irregularly marginated, and irregularly shaped mass that measured approximately 2.3 X 4.9 X 4.7 cm. This mass was causing permeative lysis of the adjacent right proximal hamulus of the pterygoid bone, ethmoid bone, and maxillary bone with complete cortical destruction and a long zone of transition, consistent with an aggressive lesion. The remaining right hamulus and adjacent maxillary and ethmoid bones had multifocal, irregularly marginated periosteal reaction (Figure 3). Other findings not pictured included mild fluid within the gravity-dependent portion of the right caudal maxillary and frontal sinuses; a smoothly marginated, ovoid mass within the ventromedial aspect of the right guttural pouch that measured 1.9 X 2.1 X 3.6 cm; multifocal periosteal proliferation and moth-eaten to permeative lysis of the left stylohyoid bone with incomplete cortical destruction and short zone of transition; and moderately thickened soft tissues of the nasopharynx and laryngopharynx. These findings made neoplasia the primary differential, but fungal etiologies could not be definitively ruled out.

Figure 3
Figure 3
Figure 3
Figure 3
Figure 3

Noncontrast transverse CT images of the skull of the horse described in Figure 1. A—Within the ventral aspect of the left guttural pouch, there is a soft tissue–attenuating, smoothly marginated, irregularly shaped mass (dashed line) that has numerous gas bubbles throughout its parenchyma. The mass is causing rightward deviation and severe narrowing of the nasopharynx (white arrow) and laryngopharynx. B—Within the right sphenopalatine sinus, there is a soft tissue–attenuating, irregularly marginated, and irregularly shaped mass (asterisk). C—The mass is causing irregularly marginated periosteal proliferation and permeative lysis of the adjacent right proximal hamulus of the pterygoid bone, ethmoid bone, and maxillary bone (black arrows) with complete cortical destruction and a long zone of transition, consistent with an aggressive lesion. D—Cross-sectional necropsy image sliced at a level similar to CT images B and C, illustrating the sphenopalatine mass (asterisk) located medial to the ramus of the mandible (white arrow) and ventral to the right side of the calvarium (pound sign). The globe has been removed, and periorbital fat is seen in its place (ampersand). The horse’s right side is toward the left of the images. Images A and B are displayed in a soft tissue window (window width, 400 HU; window level, 50 HU), while image C is displayed in a bone window (window width, 4,000 HU; window level, 500 HU). All CT images were obtained with settings of 120 kVp, 50 mA, 7,400-millisecond exposure time, 2-cm slice thickness, 512 X 512 matrix, and an 18-cm field of view.

Citation: Journal of the American Veterinary Medical Association 261, 3; 10.2460/javma.22.11.0514

Treatment and Outcome

Due to the aggressive nature and extent of the mass and the involvement of surrounding structures seen on CT, the patient was euthanized. Histopathology samples taken during necropsy revealed that the masses within the right sphenopalatine sinus (Figure 3) and left guttural pouch were squamous cell carcinomas (SCCs). The mass within the left guttural pouch was necrotic and contained remnants of a lymph node, likely due to metastatic spread from the primary sinus mass. The mass seen on CT within the right guttural pouch was an extension of the left guttural pouch mass. Given the location of the mass, the affected lymph node was likely the left medial retropharyngeal lymph node. All gross necropsy findings were consistent with the abnormalities seen on CT. However, necropsy revealed an intimate association between the sphenopalatine sinus mass and the cranial calvarium and right optic nerve, which was not fully appreciated on imaging.

Comments

While radiographs did confirm the presence of a mass in the left guttural pouch, CT was crucial in the discovery of the primary mass in the sphenopalatine sinus and the extent of the regional tissue involvement of both the primary and metastatic squamous cell carcinoma masses. Squamous cell carcinoma is the most commonly reported neoplasia in the paranasal sinuses of horses and usually originates from the oral cavity or metaplastic epithelium within the sinuses.1 These tumors are aggressive and infiltrative, and metastasis to regional lymph nodes, the pharynx, the mandible, and stylohyoid bones can occur.1 The sphenopalatine sinus can be difficult to access, and it is in close approximation with several important vascular and neural structures, making tumors in this area especially challenging to diagnose and treat.2 Clinical signs of SCC in the paranasal sinuses can vary, but the most commonly reported signs include nasal discharge, nasal obstruction, facial swelling, epiphora, blindness, and mastication problems.1 Similarly, the patient described herein presented with bilateral nasal discharge and decreased feed intake. Airway obstruction and dyspnea can occur in cases with metastasis to surrounding tissues.3 For example, the patient’s reported respiratory noise and stridor in this case were explained by the mass compressing the adjacent nasopharynx and laryngopharynx. Most affected horses have unilateral enlargement of local lymph nodes, but this is usually secondary to a reactive lymphadenopathy as only about 20% metastasize to surrounding lymph nodes.4 This makes the metastasis of the primary lesion in the sphenopalatine sinus to the presumed contralateral retropharyngeal lymph node in the left guttural pouch an interesting finding in this case.

Radiographs may be used in some cases to detect the presence of a paranasal sinus mass, but CT has become the preferred imaging modality in assessing sinus disorders in recent years.5 Since the guttural pouch is a gas-filled structure, the margins of soft tissue opaque masses are often easily seen on lateral projections because the gas acts as a negative contrast agent. Superimposition of structures with resultant border effacement makes delineating masses on the dorsoventral or ventrodorsal projection more challenging. In some cases, an oblique projection may help identify the dorsal margin of smaller masses.

Computed tomography has superior contrast resolution, eliminating the superimposition of structures seen on radiographs while providing enhanced visualization of soft tissue and bony detail. The result is better evaluation of lesion location, character, and infiltration into adjacent soft tissue and osseous structures.1 This was well illustrated with this case, as radiographs confirmed the mass in the left guttural pouch but failed to detect the sphenopalatine sinus mass. Furthermore, the extent of osteolysis and airway involvement was not appreciated with radiographs alone. The tomographic anatomy provided by CT combined with the ability to generate multiplanar reconstructions also makes it superior in cases for which planning of further therapy such as surgery or radiation is needed. The superior anatomic detail also provides prognostic information based on the location and extent of tissues involved. Imaging findings that supported the aggressive nature of the mass included the presence of 2 masses, invasion into other soft tissue and osseous structures, osteolysis with a long zone of transition and cortical destruction, and irregularly marginated periosteal proliferation. While CT findings can confirm an aggressive osteolytic soft tissue mass, there is significant overlap in imaging findings among neoplasms, as well as nonneoplastic infectious disease. Hence, a definitive diagnosis can only be made via biopsy with histopathology.1

Biopsy for histopathology can be challenging for masses in the sphenopalatine sinus. Their location can limit endoscopic access, and results may only identify secondary pathological changes if the sample was not taken from the tumor parenchyma that is deep within the mass.4 There are several described approaches for accessing masses within the sphenopalatine sinus; however, no single method can be used in every case, and none are free of the risk of complications.2

The prognosis for SCC in the paranasal sinuses is poor to grave in most cases. Once clinical signs develop and a diagnosis is made, the tumor is usually at an advanced stage and infiltration of surrounding structures is extensive. At this point, there are few, if any, effective therapeutic options, so most cases end in euthanasia at the time of diagnosis. There are no reported cases of successful treatment of SCC in the sphenopalatine sinus. For cases in which treatment is pursued, the use of multiple therapeutic modalities is recommended.4

References

  • 1.

    Kowalczyk L, Boehler A, Brunthaler R, Rathmanner M, Rijkenhuizen ABM. Squamous cell carcinoma of the paranasal sinuses in two horses. Equine Vet Educ. 2011;23(9):435440.

    • Search Google Scholar
    • Export Citation
  • 2.

    Perez JA, Hutton AE, Cudd SK, Brown JA. Standing trans-nasal endoscopic guided CO2 laser fenestration of the palatine bone to access the sphenopalatine sinus in a horse. Vet Surg. 2021;50(6):13501358.

    • Search Google Scholar
    • Export Citation
  • 3.

    McConnico RS, Blas-Machado U, Cooper VL, Reiners SR. Bilateral squamous cell carcinoma of the guttural pouches and the left middle ear in a horse. Equine Vet Educ. 2001;13(4):175178.

    • Search Google Scholar
    • Export Citation
  • 4.

    Lamb L. The challenges of equine paranasal sinus neoplasia. Equine Vet Educ. 2014;26(11):568569.

  • 5.

    Tannahill VJ. Best way to assess the sphenopalatine sinus. Equine Vet Educ. 2018;30(9):475476.

Contributor Notes

Corresponding author: Dr. Fontenot (rfontenot@cvm.msstate.edu)

In collaboration with the American College of Veterinary Radiology

  • Figure 1

    Radiographic images (left lateral [A] and dorsoventral [B]) of the guttural pouch region of a 19-year-old 509-kg American Quarter Horse mare evaluated for a 2-week history of bilateral nasal discharge, respiratory noise, and decreased feed intake.

  • Figure 2

    Same images as in Figure 1. A—There is a smoothly marginated, ovoid, soft tissue opaque mass (dashed line) within the ventral aspect of the left guttural pouch that contains stippled gas throughout. The mass is causing ventral displacement of the guttural pouch with resultant severe narrowing of the nasopharynx (white arrow). B—There is mild, smoothly marginated periosteal proliferation along the medial aspect of the left stylohyoid bone (black arrow). On the dorsoventral projection, the mass is seen as an ill-defined increase in soft tissue opacity superimposed over the left guttural pouch region, left of midline.

  • Figure 3

    Noncontrast transverse CT images of the skull of the horse described in Figure 1. A—Within the ventral aspect of the left guttural pouch, there is a soft tissue–attenuating, smoothly marginated, irregularly shaped mass (dashed line) that has numerous gas bubbles throughout its parenchyma. The mass is causing rightward deviation and severe narrowing of the nasopharynx (white arrow) and laryngopharynx. B—Within the right sphenopalatine sinus, there is a soft tissue–attenuating, irregularly marginated, and irregularly shaped mass (asterisk). C—The mass is causing irregularly marginated periosteal proliferation and permeative lysis of the adjacent right proximal hamulus of the pterygoid bone, ethmoid bone, and maxillary bone (black arrows) with complete cortical destruction and a long zone of transition, consistent with an aggressive lesion. D—Cross-sectional necropsy image sliced at a level similar to CT images B and C, illustrating the sphenopalatine mass (asterisk) located medial to the ramus of the mandible (white arrow) and ventral to the right side of the calvarium (pound sign). The globe has been removed, and periorbital fat is seen in its place (ampersand). The horse’s right side is toward the left of the images. Images A and B are displayed in a soft tissue window (window width, 400 HU; window level, 50 HU), while image C is displayed in a bone window (window width, 4,000 HU; window level, 500 HU). All CT images were obtained with settings of 120 kVp, 50 mA, 7,400-millisecond exposure time, 2-cm slice thickness, 512 X 512 matrix, and an 18-cm field of view.

  • 1.

    Kowalczyk L, Boehler A, Brunthaler R, Rathmanner M, Rijkenhuizen ABM. Squamous cell carcinoma of the paranasal sinuses in two horses. Equine Vet Educ. 2011;23(9):435440.

    • Search Google Scholar
    • Export Citation
  • 2.

    Perez JA, Hutton AE, Cudd SK, Brown JA. Standing trans-nasal endoscopic guided CO2 laser fenestration of the palatine bone to access the sphenopalatine sinus in a horse. Vet Surg. 2021;50(6):13501358.

    • Search Google Scholar
    • Export Citation
  • 3.

    McConnico RS, Blas-Machado U, Cooper VL, Reiners SR. Bilateral squamous cell carcinoma of the guttural pouches and the left middle ear in a horse. Equine Vet Educ. 2001;13(4):175178.

    • Search Google Scholar
    • Export Citation
  • 4.

    Lamb L. The challenges of equine paranasal sinus neoplasia. Equine Vet Educ. 2014;26(11):568569.

  • 5.

    Tannahill VJ. Best way to assess the sphenopalatine sinus. Equine Vet Educ. 2018;30(9):475476.

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