Veterinary Clinic Case Study

Veterinary Clinic Case Study

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A 9-year-old, spayed, female, 4.7 kg (10.4 lbs) Domestic Shorthair cat is brought to the clinic by her owner for evaluation. She has a small mass on the nasal planum that has been present for several months. The mass has recently increased in size and become ulcerated and painful. The mass was originally noted by the owner after the cat returned home from being missing for several days. This patient lives in a household with two other cats and a dog. On physical exam, her temperature is 39.4°C, heart rate is 212 beats per minute and has a respiratory rate of 60 breaths per minute. She is bright, alert and responsive. Upon palpation, you find a mild mandibular lymphadenopathy. Physical exam is otherwise unremarkable.

Results of appropriate studies return and are shown: Thoracic and abdominal radiographs: No evidence of metastases. Cytology of aspirated mandibular lymph node: Similar cells with and without granules are observed among the lymphocytes, indicating a metastasis of the nose tumor. Histopathology of the nose mass: Pleomorphic population of variably shaped neoplastic cells arranged in nests and whirls with occasional brown pigment granules in cytoplasm, marked anisocytosis and anisokaryosis and frequent mitotic figures. Findings are consistent with a malignant neoplasm.

About the case

Cutaneous malignant melanoma is rare in cats and in most domestic species except for dogs, in which it is common. Feline non-ocular melanomas have been reported in Domestic Shorthair cats of all ages, but there is no apparent sex or color predilection. The majority of tumors occur on the head, most frequently the nares, forehead, base of ear and pinna. Metastases are commonly found in regional lymph nodes. Treatment is primarily surgical excision with additional therapies including radiation, chemotherapy and vaccination. Studies involving cats are not numerous enough to make survival predictions, but poorly pigmented tumors and evidence of metastases are associated with a poor prognosis. The tumors are derived from melanocytes that are of neuroectoedermal origin. Malignant melanoma resembles the more common benign counterpart with less pigmentation and wide variation in cell morphology and arrangement. This variability complicates the cytologic and histopathologic diagnosis. On cytologic specimens, groups of cells may appear to be of epithelial origin (occurring in clusters) or mesenchymal origin (individual oval to spindle-shaped cells) or appear as discrete, round cells. Advances in immunohistochemical staining are helping to diagnosis poorly pigmented tumors.