Metastatic carcinoma presenting as hind-limb lameness: diagnosis by synovial fluid cytology

A dog presented for evaluation of left hind-limb lameness and pain associated with manipulation of the tail. Synovial metastasis of a carcinoma was diagnosed by joint fluid examination. A primary bronchiolar-alveolar carcinoma with widespread (including synovial and skeletal) metastases was diagnosed on postmortem examination. Metastasis to synovial surfaces is uncommon, but when it occurs, the metastasis-induced arthritis may be the initial presenting complaint for which medical attention is sought. Although rarely reported, cytological examination of synovial fluid may be diagnostic. This paper presents an interesting clinical case and reviews the literature concerning metastatic disease of the synovium.