Primary malignant melanoma of the transverse colon: report of a case and review of the literature.

Gastrointestinal involvement by malignant melanoma is predominantly a metastatic phenomenon. Although primary malignant melanoma of the gastrointestinal tract has been documented in the esophagus, stomach, small bowel, and anorectum, the incidence of primary melanoma of the colon is rare and remains controversial in most cases. We present a case of solitary malignant melanoma of the transverse colon occurring in a 64-year-old African American male patient.

S100A4 protein and mesothelin expression in dysplasia and carcinoma of the extrahepatic bile duct.

We evaluated the expression of S100A4 protein and mesothelin in dysplasia and carcinoma of the extrahepatic bile duct (EBD) and their potential use as adjuncts for differentiating carcinomatous and significant high-grade dysplastic epithelium from reactive or inflammatory glandular atypia of the EBD. We used immunohistochemical analysis on formalin-fixed tissue sections from 10 cases of carcinoma, 6 cases of high-grade dysphasia (HGD), 4 cases of low-grade dysplasia (LGD), and 10 cases of benign or reactive or inflammatory epithelium from the EBD. Expression of S100A4 protein was observed in 8 invasive carcinomas (80%), 5 HGD/carcinoma in situ cases (83%), and 0 LGDs.