Suspected unusual digital metastases of a primary renal cell carcinoma in a cat

An 8-year-old neutered male domestic shorthair cat was presented for exploration of a renal mass. Abdominal ultrasonography revealed a thick, anechoic, and irregular band partially encapsulating the left kidney with a thick echoic capsule and numerous thick echoic striations. Cytologic examination revealed moderate serosanguineous and chronic inflammatory effusion without atypical cells or causative agents. Swelling around several digits of both forelimbs and a small eyelid nodule appeared several days later. Radiographs of both forelimbs revealed aggressive osteolytic lesions of the distal phalanges of several weight-bearing digits. Thoracic radiographs were unremarkable. Despite the aggressive digital lesions, the owners decided to pursue the laparoscopy on the same day. The content of the cyst-like mass around the left kidney was aspirated, and the thick and firm wall was fenestrated. The ventral aspect of the wall was resected as much as possible. Histopathologic analysis revealed an ill-defined renal cell carcinoma with marked necrosis and suspected vascular embolization, as well as a solid carcinoma with respect to the eyelid lesion. Cytologic analysis of the digital lesions revealed malignant carcinomatous infiltration, presumed to be metastatic due to the multiple locations of the lesions. Key clinical message: Multifocal digital metastases may have a primary neoplastic origin other than pulmonary in cats. In the presence of multiple and aggressive digital lesions in a cat with no lung mass, the search for a primary tumor other than pulmonary must be carried out.