Gastrointestinal manifestations of Malignant Melanoma – Observations from a single center study

Background: Gastrointestinal manifestation of malignant melanoma (GMM) is a rare entity. It usually occurs as a metastasis of extra-intestinal malignant melanoma (MM), but rarely no primary tumor can be detected. Histopathological differentiation from other gastrointestinal (GI) malignant tumors is challenging. Methods: All GMM cases diagnosed between 2004 and 2014 were retrieved from the histopathological database of the 1st Department of Pathology and demographic, clinical and pathological parameters were analyzed. Results: During the 11-year study period 14 GMM cases were found. In 4 cases, despite extensive diagnostic workup, no primary tumor could be detected. The most common location of GMM was small intestine in 6 cases, followed by rectum in 4 cases, upper GI tract in 3 cases and colon in 2 cases. In 2 cases multiple locations were affected, simultaneous liver metastases were present in 6 cases. Age at diagnosis was ranging from 26 to 75, gender distribution was similar (7 males, 7 females), females (mean age: 67 years) tended to be older than males (mean age: 62 years). Cases in the upper GI tract and small intestine were younger than cases in the colorectum. Immunohistochemical stainings (S-100, Melan- A, HMB-45) for MM were highly positive. Conclusions: MM can manifest in the entire GI tract either as a primary or as a metastatic malignancy. It affects both genders equally. Small intestine and rectum seems to be the most common location. Although a rare entity, GMM should be considered as a differential diagnostic possibility of GI tumors, especially in cases with a history of MM. This study was supported by the Hungarian Scientific Research Fund (OTKA-K111743 grant).