Mucinous Rectal Adenocarcinoma in a Urutu Snake (Bothrops alternatus).

A 15-year-old captive female Urutu snake (Bothrops alternatus) was presented with anorexia, apathy, dehydration, pale mucous membranes and marked enlargement of the caudal third of the coelomic cavity. Radiographs and ultrasonography were suggestive of faecal impaction or neoplasia. Post-mortem findings consisted of solid faecal impaction of the intestines, secondary to obstruction caused by a rectal tumour. Cytological examination of impression smears of the tumour revealed polygonal to round neoplastic cells arranged in clusters in an abundant extracellular mucinous matrix. Histologically, there was transmural growth of neoplastic epithelial cells arranged in small nests or individually and immersed in abundant extracellular mucin lakes. The neoplastic cells were immunopositive for cytokeratin. Clinical and pathological aspects indicated a diagnosis of mucinous rectal adenocarcinoma.