Squamous cell carcinoma of unknown primary origin in a dog presenting with bone metastasis.

A 10-year-old female American Pit Bull dog was diagnosed with metastatic undifferentiated carcinoma of the scapula. Immunohistochemistry showed positive immunoexpression for cytokeratins (AE1/AE3, 34BE12, CK7) and vimentin, confirming squamous cell carcinoma. No evidence of nodules was found in the complete physical examination and imaging procedures conducted. The patient was diagnosed with carcinoma of unknown primary origin. Amputation and adjuvant chemotherapy with doxorubicin and piroxicam were performed, but the patient died of respiratory failure after 737 days of diagnosis. Necropsy confirmed undifferentiated carcinoma infiltrating the lungs and kidneys, and showing the same immunoexpression as the tumor in the scapula. Amputation associated with chemotherapy extended the overall survival time of this patient.

Melanoma of unknown primary origin metastasizing to visceral organs in a sheep

Malignant melanomas are quite uncommon in sheep and goats. A three-year-old native female sheep with a history of sudden death was referred for postmortem examination. Gross evaluations revealed multiple brown to black neoplastic masses with compact nodular appearance, involving lungs, mediastinal lymph nodes, liver and kidneys. Comprehensive physical examination of skin, all mucous membranes and mucocutaneous junctions revealed no evidence of concomitant pigmented lesions or dark discoloration. Microscopically, the masses were predominantly composed of round and polyhedral-shaped neoplastic cells of various sizes with abundant pale eosinophilic cytoplasm containing variable amounts of dark brown melanin pigment and peripherally located, oval to round, vesicular nuclei with prominent nucleoli. Immunohistochemically, the neoplastic cells displayed diffuse and positive expression for S100 protein, vimentin and melan-A. These histopathological and immunohistochemical findings were consistent with a final diagnosis of metastatic malignant melanoma, “epithelioid” type. To the author knowledge, metastatic melanoma without an identified primary origin has not yet been reported in the domestic animals.(AU)

Melanoma of unknown primary origin metastasizing to visceral organs in a sheep

Malignant melanomas are quite uncommon in sheep and goats. A three-year-old native female sheep with a history of sudden death was referred for postmortem examination. Gross evaluations revealed multiple brown to black neoplastic masses with compact nodular appearance, involving lungs, mediastinal lymph nodes, liver and kidneys. Comprehensive physical examination of skin, all mucous membranes and mucocutaneous junctions revealed no evidence of concomitant pigmented lesions or dark discoloration. Microscopically, the masses were predominantly composed of round and polyhedral-shaped neoplastic cells of various sizes with abundant pale eosinophilic cytoplasm containing variable amounts of dark brown melanin pigment and peripherally located, oval to round, vesicular nuclei with prominent nucleoli. Immunohistochemically, the neoplastic cells displayed diffuse and positive expression for S100 protein, vimentin and melan-A. These histopathological and immunohistochemical findings were consistent with a final diagnosis of metastatic malignant melanoma, “epithelioid” type. To the author’ knowledge, metastatic melanoma without an identified primary origin has not yet been reported in the domestic animals.