ANORECTAL MALIGNANT-MELANOMA - A CLINICOPATHOLOGICAL STUDY, INCLUDINGIMMUNOHISTOCHEMISTRY AND DNA FLOW-CYTOMETRY

BACKGROUND, Anorectal malignant melanoma is a rare tumor with an extre mely poor prognosis. DNA flow cytometric study as well as detailed imm unohistochemical study have not been reported previously. METHODS, Eig hteen cases of anorectal melanoma were studied, including immunohistol ogy for melanoma markers and epithelial markers and DNA flow cytometri c study of paraffin blocks. RESULTS. Most patients were Ashkenazi Jews , compared with Sephardi Jews and Arabs. Of the 17 patients followed, 14 died of disease at 4-39 months from presentation. Three patients we re alive with disease at 12, 53, and 72 months of follow-up. Tumor thi ckness ranged from 3-35 mm (mean, 12.8 mm). The 2 long term survivors had tumor thickness less than or equal to 7 mm. No correlation was fou nd between the mode of primary surgical treatment (8 patients: abdomin operineal resection; 10 patients: local excision) and outcome. Vimenti n, HMB-45, and S-100 protein stainings were positive in 18, 17, and 15 tumors, respectively. Polyclonal carcinoembryonic antigen (CEA), broa d-spectrum cytokeratin, epithelial membrane antigen, monoclonal CEA, a nd TAG-72 (B72.3) stainings were positive in 13, 3 (only focal and rar e staining), 2, 0, and 0 tumors, respectively. Thirteen tumors had ade quate material for DNA analysis, and all were DNA aneuploid. S-phase f raction could be assessed in 11 tumors and ranged from 7.7-24% (mean, 14%). An S-phase fraction of < 10% was observed in the 2 long term sur vivors. CONCLUSIONS. Anorectal melanoma in this study carried a grave prognosis. The frequent staining for polyclonal CEA (with negative mon oclonal CEA staining) was probably due to nonspecific cross-reacting a ntigens. The occasional staining for epithelial markers warrants a com prehensive immunohistochemical study to ensure a correct diagnosis, es pecially in small biopsies of amelanotic undifferentiated tumors that lack junctional changes. The aneuploidy of all tested tumors reflected their highly malignant behavior. A trend toward longer survival was o bserved in patients with thin tumors and an S-phase fraction of < 10%. However, due to the small number of survivors, the latter observation should be further tested in a larger scale series. (C) 1997 American Cancer Society.