Cutaneous and subcutaneous metastases of gastrointestinal stromal tumors: a series of 5 cases with molecular analysis.

Gastrointestinal stromal tumors (GISTs) rarely metastasize to the skin. We describe 5 patients with GIST with subcutaneous and cutaneous metastases. The mean age at metastasis was 54 years (range 30-68 years) with a male predominance (4:1). Primary tumors occurred in the stomach (n = 3), small bowel (n = 1), and abdomen, not otherwise specified (n = 1). The average time from primary tumor resection to the resection of skin metastases was 59 months (range 11-155 months). The metastases occurred in the scalp (n = 2), cheek (n = 1), and abdomen (n = 2) with 3 patients presenting with solitary nodules and 2 patients with multiple nodules. The average size was 2 cm (range 0.6-4 cm). Histologically, 2 cases were spindled and 3 cases demonstrated mixed epithelioid and spindle cell morphology. All were confirmed to have CD117 reactivity. KIT genotyping was performed in 4 of 5 cases. Two cases harbored a mutation in exon 11, and the remaining 2 cases were wild type in exons 9, 11, 13, and 17. All 5 patients had multiple concurrent or subsequent abdominal and/or hepatic metastases. In 4 patients with an average follow-up of 32 months (range 6-75 months), after the resection of the metastases, 2 were alive with disease and 2 died of disease. Cutaneous metastases seem to be a late complication of GIST, but their presence does not necessarily herald a rapid demise of the patient.