Brain and ocular carcinomatosis diagnosed ante-mortem by cerebrospinal fluid and aqueous humor cytology in a dog

A 9-year old female cocker spaniel dog was presented with uveitis, blindness and neurological signs, with a history of mixed malignant mammary tumor that had been excised two months prior to presentation. Brain and ocular metastasis of mammary adenocarcinoma, with meningeal carcinomatosis (MC) were diagnosed by both cerebrosspinal fluid (CSF) and the aqueous humor (AH) cytology, which revealed numerous cells, with overall morphology compatible with epithelial secretory origin, demonstrating malignant characteristics. The morphologic diagnosis was a secretory cell carcinoma, most probably of mammary gland origin. The dog was euthanized at its owners’ request. Gross pathology showed multiple nodular masses of variable diameter (3 to 20 mm) on examination of the right ventral thalamus, inguinal mammary lymph nodes and lungs. Microscopic examination revealed neoplastic epithelial cell infiltrating the leptomeninges, brain parenchyma, inguinal mammary lymph nodes, eyes and lungs. The neoplastic cells were cytokeratin-positive, vimentin-negative, supporting their epithelial origin. The definitive diagnosis was malignant mixed mammary tumor with distant metastases to various organs, and MC. In this case, both CSF and AH cytological analyses were useful for the ante-mortem diagnosis of mammary carcinoma, MC and ocular metastases. These finding along with brain computed tomography suggested brain metastases.