Mimicry in older patients: tophaceous pseudogout as a tumorlike lesion: a case report.

Pseudogout is frequently seen in painful arthritis of larger joints, especially the knees and shoulders. This case report describes a rare clinical entity of soft-tissue calcium pyrophosphate dihydrate crystal deposition disease surrounding the second metatarsal bone of an 81-year-old man with moderate painful swelling of the right forefoot for 2 years. Diagnostic imaging demonstrated a calcified soft-tissue tumor adjacent to the second metatarsal bone by considering a neoplastic process in the differential diagnosis. Excisional biopsy revealed a chalklike material on the calcified soft tissue that was pathognomonic for chondrocalcinosis or pseudogout. The excisional biopsy findings led to stagnation of the clinical symptoms, and no recurrence of the initial tumor was seen during 12-month follow-up. In the literature, only 28 cases of tophaceous pseudogout tumors in the extremities have been described. In these cases, the lesions were suspected of being chondrosarcomas. For this reason, a correct diagnosis has to be pursued by performing a biopsy to treat the disease correctly.