Gastrointestinal Stromal Tumor Markers in Cutaneous Melanomas

Melanoma expresses c-kit, a gastrointestinal stromal tumor marker, but has not been extensively evaluated for protein kinase C theta (PKC theta) or DOG1, and these stains have not been correlated with prognostic factors. We immunostained 62 primary cutaneous and 15 metastatic melanomas for polyclonal c-kit (pc-kit), monoclonal c-kit (mc-kit), PKC theta, and DOG1 and correlated results with prognostic parameters and survival. Of the cutaneous melanomas, 34 (55%) stained for pc-kit, 30 (48%) for mc-kit, 11 (18%) for PKC theta, and 2 (3%) for DOG1. The Breslow depth was 1.00 mm or less in 21 (68%) of 31 pc-kit+ cutaneous melanomas compared with 7 (27%) of 26 pc-kit- melanomas (P = .002). The pc-kit+ melanomas had less nodal disease (1/31 [3%] vs 9/25 [36%]; P = .001) and local recurrence (1/33 [3%] vs 6/27 [22%]; P = .021) but no statistically significant difference in the rate of distant metastases (13/32 [41%] vs 14/27 [52%]; P = .388) or survival (10/34 [29%] vs 16/39 [41%]; P = .301). We found that pc-kit correlates better with prognostic parameters than does mc-kit.