Anorectal melanoma – histopathological and immunohistochemical features and treatment

Abstract

Anorectal melanomas should be characterized by location (anal, rectal and anorectal), color, size, shape and mobility and microscopically, by melanocyte subtypes, grade of melanin pigmentation, junctional changes in the squamous epithelium, atypical mitotic index, cellular atypia, inflammatory infiltrate, vascular and perineural invasion, sentinel lymph node, and anorectal parietal penetration. Anorectal melanomas must be staged by American Joint Committee on Cancer (AJCC) and/or TNM Classification of Malignant Tumours (TNM) criteria. As melanocytes can present with several shapes, sometimes the differential diagnosis with other tumors in this region may be difficult. Because of this, immunohistochemistry is mandatory to attain a precise diagnosis. This study is a report of 14 patients with anorectal melanoma, in whom histological examinations were remade and immunohistochemistry was performed with several markers for melanocytes and for other tumor cells of the anorectal region, properly establishing the diagnosis. The most rational surgery is the extended local resection, when the disease is restricted to the area or the abdominoperineal resection to advanced lesions. Regardless of the technique used, the results are always poor. The authors deny any efficacy of current radio and/or chemotherapy as part of treatment of anorectal melanoma. Target-therapy for metastatic disease has been considered a good strategy, but the results are still inconclusive.

A case report of anorectal malignant melanoma in the transitional zone

“…Histological examination describes the pigmented lesions is based on the presence and location of atypical melanocytes. Immunohistochemical studies are mostly positive for protein S-100, melanoma antigen HMB-45, and vimentin, whereas positive staining for carcinoembryonic antigen, cytokeratin, epithelial membrane antigen is suggestive of adenocarcinoma [ 11 , 9 ].…”

Spindle cell proliferations of the sigmoid colon, rectum and anus: a review with emphasis on perineurioma

“…Metastatic melanoma to the sigmoid colon, rectum and anus is rarely encountered; there may be long disease‐free intervals after diagnosis of the primary cutaneous tumour . The histopathological and immunohistochemical features of primary and metastatic melanoma in the anorectum (Figures and ) are the same as for melanoma at other sites . Melanoma is well known as the ‘great imitator’ of both benign and malignant entities; therefore, accurate diagnosis of this morbid malignancy relies on pathologists having a high index of suspicion.…”

Melanoma anal: relato de caso raro e revisão de literatura

“…6,7 A etiologia dos melanomas anorretais é associada a exposição da pele a raios ultravioletas, o que explica a raridade deste tumor na região anorretal, área geralmente não exposta. 8 Entre todos os melanomas, 0,4% a 1,6% surgem na região anorretal, sendo o canal anal o sítio mais frequente de melanoma depois da pele e retina. 2,5,8 A distribuição é similar em homens e mulheres, com uma discreta predileção pelo sexo feminino, com idade média de apresentação do tumor na sexta e sétima década de vida.…”

“…8 Entre todos os melanomas, 0,4% a 1,6% surgem na região anorretal, sendo o canal anal o sítio mais frequente de melanoma depois da pele e retina. 2,5,8 A distribuição é similar em homens e mulheres, com uma discreta predileção pelo sexo feminino, com idade média de apresentação do tumor na sexta e sétima década de vida. 1,2,9 O grande fator de risco para o melanoma cutâneo, a exposição aos raios ultravioletas não esteve tão relacionada ao melanoma maligno anal.…”

“…Os únicos fatores de risco identificados incluem história familiar e uma mutação de ativação de C-KIT. 1,2,8 Sua sintomatologia é extremamente inespecífica, o que retarda ainda mais o diagnóstico. Proporcionalmente, 14 -78% dos pacientes apresentaram sangramento perianal; dor perianal esteve presente em 7 -27% dos casos; 9 -20% dos pacientes apresentaram massa perianal; constipação ocorreu em 6 -9% dos pacientes e diarreia esteve presente em 1 -4%.…”