Clinicopathologic characteristics of esophageal primary malignant melanoma

Malignant melanoma is a rare tumor that commonly occurs in the skin; however, it can also develop in other sites, including the esophagus, oral cavity, sinonasal tract, anorectal region, vagina, and eye. Esophageal primary malignant melanoma (EPMM) accounts for approximately 0.2–0.3 % of all malignant esophageal tumors. The mean age of patients who develop EPMM is 61 years (range 21–90 years). EPMM predominantly affects males (male to female ratio 2.4:1). The tumor preferentially occurs in the lower and middle part of the thoracic esophagus and commonly appears as a polypoid mass. Histologically, it is composed of polygonal or spindle cells with atypical nuclei and varied amounts of melanin pigment in the cytoplasm. Immunohistochemical stains for S-100 protein, HMB-45, and Melan-A are useful for a correct pathological diagnosis. EPMM often has scattered lesions and occasionally melanocytosis around the main tumor. EPMM and malignant melanomas occurring in other organs exhibit aggressive biological behavior. A review of autopsy cases indicates that EPMM commonly metastasizes to the lymph nodes (82 %), liver (72 %), lung (69 %), peritoneum (45 %), and bone marrow (41 %). Although improved survival with the molecular targeting agent vemurafenib has been demonstrated in cutaneous melanoma with BRAF ^V600E mutation, recent evidence indicates that EPMM has genetic alterations unique from those observed in cutaneous and other mucosal melanomas. Since information regarding the genetic features of EPMM is limited, further progress in understanding the molecular pathology of this disease is required for the development of novel therapeutic strategies. This paper aims to review previously reported EPMM cases to clarify its clinicopathologic features that could aid in the development of effective therapeutic strategies.