Malignant melanoma, GIST, MPNST, sarcomatoid renal cell carcinoma, and malignant fibrous histiocytoma will be positive for vHMB-45, c-kit, S-100, RCC marker, and CD68, respectively, and will be negative for desmin, synaptophysin, inhibin, Melan-A, and calretinin. The gene discussed is KIT; the disease is melanoma.