History
A 10-year-old male neutered domestic longhair cat weighing 6.6 kg was presented to the University of Georgia College of Veterinary Medicine Small Animal Internal Medicine Service for worsening of a chronic nonproductive cough present since 1 year of age and a 1-month history of lameness on the left thoracic limb, with no other significant health history. The cough was previously managed with oral maropitant for around 1 year. The patient was an indoor-outdoor cat, was up to date on rabies vaccinations, and received monthly flea and tick prevention.
Clinical and Gross Findings
On physical examination, the cat was overweight with a body condition score of 7/9. The left thoracic limb was painful on palpation, and there were increased bronchovesicular sounds bilaterally. On a sedated examination, the third and fourth digits were found to have overgrown nails penetrating the paw pads. Radiographs of the left thoracic limb showed marked lysis of P3 of digits 3 and 4. Thoracic radiographs showed multifocal, ill-defined, cavitated soft tissue opacities in the left and right caudal lung lobes, along with a moderate diffuse interstitial pattern in the remaining lung fields. A transtracheal wash showed large numbers of neutrophils, fewer macrophages, and rare lymphocytes, consistent with neutrophilic inflammation. Few extracellular bacteria were present, occasionally adhered to squamous epithelial cells and presumed to be contamination. Culture did not reveal any bacterial growth.
Following diagnostics, the overgrown nails were trimmed, and the cat was sent home on oral maropitant and a fluticasone inhaler for presumptive chronic bronchitis, with instructions to monitor the cough and lameness.
After discharge, the front limb lameness did not improve, and the cat re-presented around 3 weeks later for persistent bleeding of the left thoracic and right pelvic paws, which progressed to include bleeding of the right thoracic paw. The cat was sedated, and a fine-needle aspirate was performed on the left thoracic and right pelvic paws; cytology is shown (Figure 1).
Photomicrograph of a cytology of the ulcerated digit from a 10-year-old cat presenting for reevaluation of lameness and bleeding digits. A—Numerous aggregates of cuboidal to fusiform neoplastic cells with round, basophilic nuclei are present throughout the slide. Wright-Giemsa stain; bar = 50 μm. B—Cells have round, paracentral nuclei, pale basophilic cytoplasm with moderate eosinophilic granulation (thin arrow), and occasional apical cilia (thick arrow). Wright-Giemsa stain; bar = 20 μm.
Citation: Journal of the American Veterinary Medical Association 261, 5; 10.2460/javma.22.09.0415
Formulate differential diagnoses, then continue reading.
Cytologic and Histologic Findings
Cytology showed numerous clusters of columnar to fusiform epithelial cells. Cells had basophilic cytoplasm, rounded eccentric nuclei with coarsely stippled chromatin, and up to 3 nucleoli. There was moderate anisocytosis and anisokaryosis. Eosinophilic granules were sometimes noted in the cytoplasm, and some cells had apical, slender, hair-like structures consistent with cilia. A moderate number of degenerate neutrophils and rare macrophages were present. The cytologic diagnosis was metastatic carcinoma with mixed neutrophilic and histiocytic inflammation. The top differential was metastatic pulmonary adenocarcinoma given the history of radiographic lung lesions, lesions on multiple paws, and presence of ciliated columnar epithelium and likely goblet cells.
The cat did not fully recover from sedation and was euthanized due to grave prognosis and poor expected quality of life. A necropsy was performed after euthanasia.
On necropsy, all lung lobes were moderately to markedly expanded by numerous tan to cream-colored, firm, discrete to coalescing nodules, at times markedly distorting the pulmonary lobar structure and occasionally displaying central cavitation. The third digit of the right thoracic and third and fourth digits of the right pelvic limbs were grossly enlarged (Figure 2). Histopathology of the lungs and digits was performed (Figure 3). The lungs showed effacement of around 90% of normal parenchyma by a dense, poorly demarcated, and unencapsulated population of neoplastic cells. Cells had an acinar arrangement, frequently extended from peribronchial tissue, and were supported by a dense desmoplastic stroma. Cells were cuboidal to columnar with round central nuclei and a moderate amount of eosinophilic granular cytoplasm. Anisokaryosis and anisocytosis were moderate, and there were 2 mitotic figures/2.4 mm2 (equivalent to 10 FN22/40 X fields). Lymphatic invasion was identified. Histopathology of the digits showed a similar population of cells; there was moderate effacement of the distal phalange and dermis with cuboidal to columnar, pseudostratified, occasionally ciliated epithelial cells arranged in acini, with moderate intraluminal mucus, supported by a desmoplastic stroma. Marked bone lysis was present.
Gross photographs of the lungs and paw from a 10-year-old cat at necropsy with lung-digit syndrome. A—Gross photograph of the lungs; all lung lobes were expanded by numerous multifocal to coalescing, firm, tan to cream-colored nodules with occasional central cavitation. B—Gross photograph of the right thoracic paw; digit 3 was enlarged and dark red to purple, measuring 2 X 1.5 X 1 cm.
Citation: Journal of the American Veterinary Medical Association 261, 5; 10.2460/javma.22.09.0415
Photomicrographs of histology from the lung and digits of a 10-year-old cat with lung-digit syndrome. A—There is multifocal, severe effacement of normal lung parenchyma by neoplastic epithelial cells. Cells are arranged in acini and are columnar to cuboidal with basilar nuclei and moderately distinct cell borders. H&E stain; bar = 20 μm. B—P3 shows multifocal bone lysis with areas of cellular infiltrate and irregular acini within the bone and surrounding soft tissue. The inset shows an acinus surrounded by hemorrhage and inflammatory debris, containing multiple layers of cuboidal to columnar, ciliated cells with basophilic nuclei; occasional goblet cells are also present. This population is consistent with neoplastic pulmonary epithelium. H&E stain; bar = 200 μm; inset bar = 20 μm.
Citation: Journal of the American Veterinary Medical Association 261, 5; 10.2460/javma.22.09.0415
Diagnosis
Pulmonary adenocarcinoma with digital metastasis (lung-digit syndrome).
Comments
At initial examination, pulmonary carcinoma was considered as a differential diagnosis, but given the presence of a 9-year history of symptomatically managed cough and the presence of ingrown claws on the grossly affected toes, the respiratory symptoms and lameness were treated as separate nonneoplastic issues. Cytology of the digits was only pursued upon re-presentation due to progression of lameness and bleeding to additional paws. Cytologic findings of the digit fine-needle aspirate were consistent with ciliated columnar epithelial and goblet cells, consistent with digital metastasis of pulmonary adenocarcinoma (lung-digit syndrome) given the clinical history and radiographic findings of the patient.
Primary pulmonary tumors are relatively uncommon in cats, composing between 0.69% and 0.75% of feline biopsy samples.1 These tumors tend to be found in middle-aged to older cats, with an increased prevalence in Persians, and are most commonly found to be adenocarcinomas.1–3 Affected cats most often present with coughing, anorexia, lethargy, and weight loss, although 20% of cats in 1 study3 were asymptomatic and diagnosed due to incidental findings on thoracic radiographs. Initial diagnosis is usually made based on the presence of 1 to several frequently cavitated masses seen on thoracic radiographs in the absence of other primary tumors.3 The treatment of choice for pulmonary carcinoma in cats is surgery. Due to the difficulty and morbidity involved in sampling intrathoracic masses for biopsy, treatment decisions and prognosis are determined using severity of clinical signs and WHO staging criteria; any nodal or distant metastasis, presence of pleural effusion, or dyspnea upon presentation is associated with poor prognosis and mean survival times of < 3 days with lung lobectomy.3 For cats in which surgery is performed, histologic criteria are prognostically significant; cats with well-differentiated tumors have higher mean survival times than cats with intermediate or poorly differentiated tumors.2,3
Pulmonary carcinoma has a higher metastatic rate and more aggressive behavior in cats than in dogs.1–3 The most common metastatic sites are intrapulmonary, thoracic lymph nodes, and pleural cavity (carcinomatosis), though extrathoracic metastasis occurs in up to 16% of cases.2 Unique to feline pulmonary carcinoma, distal digit metastasis has been repeatedly documented, and as in this case, lameness is sometimes the presenting complaint leading to diagnosis.1,4 Feline digits are often amputated for presumed recurrent or unresolving bacterial infections of the nail bed, but 74% of amputated digits were found to have neoplastic disease present in 1 study,5 with 20.6% of neoplasms diagnosed as metastatic adenocarcinoma. This prevalence suggests that although feline lung-digit syndrome is considered uncommon, thoracic radiographs should always be performed before amputating a digit due to chronic or recurrent disease in cats. Likewise, amputated digits should always be submitted for histopathology, as cats with digital metastases from pulmonary adenocarcinoma have a very poor prognosis and short survival time after surgery.4,5
References
- 1.↑
D’Costa S, Yoon BI, Kim DY, Motsinger-Reif AA, Williams M, Kim Y. Morphologic and molecular analysis of 39 spontaneous feline pulmonary carcinomas. Vet Pathol. 2012;49(6):971–978.
- 2.↑
Hahn KA, McEntee MF. Primary lung tumors in cats: 86 cases (1979–1994). J Am Vet Med Assoc. 1997;211(10):1257–1260.
- 3.↑
Maritato KC, Schertel ER, Kennedy SC, et al. Outcome and prognostic indicators in 20 cats with surgically treated primary lung tumors. J Feline Med Surg. 2014;16(12):979–984.
- 4.↑
Gottfried SD, Popovitch CA, Goldschmidt MH, Schelling C. Metastatic digital carcinoma in the cat: a retrospective study of 36 cats (1992–1998). J Am Anim Hosp Assoc. 2000;36(6):501–509.
- 5.↑
Wobeser BK, Kidney BA, Powers BE, et al. Diagnoses and clinical outcomes associated with surgically amputated feline digits submitted to multiple veterinary diagnostic laboratories. Vet Pathol. 2007;44(3):362–365.
