Renal cell carcinoma metastatic to the thumb: a case report and review of subungual metastases from all primary sites.

Subungual metastatic cancer from any primary site is rare. Only seven cases from primary renal cell carcinoma have previously been reported. We now describe a further example of this condition and review its clinical features, radiographic findings and pathological changes. The diagnosis of subungual metastasis should be considered in any patient with metastatic cancer who develops a new lesion of the distal phalanx.