Meningeal carcinomatosis in two cats.

Multifocal to diffuse meningeal infiltration by neoplastic epithelial cells was observed in two aged cats with neurological signs and a history of surgical ablation of the auricular pinnae because of the presence of squamous cell carcinoma. In both cats, examination of the external ear canals revealed neoplastic lesions consistent with squamous cell carcinoma, but no changes of the tympanic bullae were noted. In one cat, post-mortem examination revealed marked thickening of the dura mater and infiltration of the arachnoid layer by cytokeratin-positive, neoplastic epithelial cells. In the other cat, no macroscopic brain lesions were noted, but multifocal dissemination of neoplastic epithelial cells to the leptomeninges was observed histologically. Several pathways by which neoplastic cells can reach the meninges have been suggested and haematogenous dissemination was considered most likely in these cats. Squamous cell carcinoma is the most common cutaneous malignant neoplasm in cats and meningeal carcinomatosis can be considered a rare complication.