Year: 2018
Type: conference-abstract
Abstract: The vast majority of gastrointestinal melanomas are metastatic in nature. Whether primary colorectal melanoma exists is still controversial. Case study. Case Summary: A 32-year-old African American male patient presented with a history of anemia for 2.5 years. Clinical workup revealed sickle cell trait and iron deficiency anemia. There was no rectal bleeding. Colonoscopy showed a 1-mm black pigmented region in the mucosa of the distal rectum near the anorectal junction. On pathologic examination, H&E sections showed an increased number of melanocytes. The melanocytes were enlarged. Immunohistochemical stains for S100, HMB45, Melan-A, and SOX10 highlighted melanocytes in the mucosa with prominent dendritic processes. The cytological atypia was mild. A follow-up flexible sigmoidoscopy performed 2 months later revealed a small mucosal scar where the original pigmented lesion had been biopsied. This specimen demonstrated benign colonic mucosa without any melanocytes detected by melan-A, HMB-45, and SOX-10. A thorough medical history and detailed physical examination revealed no primary melanoma elsewhere, including the skin or ocular area. Anorectal mucosal colonic melanoma (ARMM) is a rare tumor. Typically, gastrointestinal melanomas are most often the result of metastases from a cutaneous site. Although anorectal melanoma is generally believed to arise from melanocytes distal to the dentate line that extend into the distal rectum, the presence of melanocytic cells within the epithelium of the distal rectum, in our case, supports the argument that a colonic mucosal melanoma can arise from melanocytes in the distal rectum and thus give rise to primary anorectal mucosal melanoma. Here we report a case of tissue obtained during a colonoscopy showing an atypical intramucosal melanocytic cell proliferation in the distal rectum. This provides evidence supporting that primary melanoma could potentially arise from primary melanocytic lesions in the colon.
Authors: Bin Zhang, Robert Strauss, Anna Moran, Paul Zhang, Xiaowei Xu
Institution: University of Pennsylvania Health System
Language: English
Subfield: Oncology
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2891308063