Primary malignant melanoma of the oesophagus: a clinical and pathological study with emphasis on the immunophenotype of the tumours for melanocyte differentiation markers and cancer/testis antigens.

SUMMARY: Primary malignant melanomas of the oesophageal squamous mucosa are exceedingly rare. We present here the clinical and pathological findings of 10 patients (mean age 64 years) with primary oesophageal melanoma, with emphasis on the immunophenotype of the tumours. The majority of melanomas were located in the mid to distal oesophagus and were large (mean tumour size at the time of diagnosis 6.2 cm; mean depth of invasion 1.86 cm). All but two of the melanomas were associated with an extensive in situ component. Half of the tumours were amelanotic. The histological spectrum was wide, including appearances mimicking lymphoma, poorly differentiated adenocarcinoma or sarcoma. Immunohistochemical studies were performed on six tumours using monoclonal antibodies (MAb) to S100 protein, tyrosinase (MAb T311), Melan-A (MAb A103), and gp100 (MAb HMB-45), as well as antibodies to five cancer/testis (CT) antigens (MAb CT7-33 to CT7/MAGE-C1, MAb ESO121 to NY-ESO-1, MAb 57B to MAGE-A4, MAb MA454 to MAGE-A1, and MAb M3H67 to MAGE-A3). Seven patients had metastatic disease at the time of presentation. All but one patient underwent resection of the tumour with negative surgical margins. Survival was poor, with a mean survival of 19.8 months. One patient, however, whose tumour was limited to the submucosa, is still alive 108 months post-oesophagectomy. All six melanomas examined by immunohistochemistry were positive for all the melanocyte differentiation markers tested. In addition, they were all positive for CT antigens, with MA454 being the most commonly found, suggesting that CT antigens may be a promising immunotherapeutic target for oesophageal melanomas.