Primary gastric malignant melanoma: challenge in preoperative diagnosis

Abstract

Primary gastric melanoma is an extremely rare clinical entity. The clinical manifestation is not specific and usually similar with other common malignancies at this site, such as gastric cancer and lymphoma. And there are no specific radiological features either. Preoperative diagnosis via biopsy is usually difficult, since melanoma pigment could be absent in the biopsy tissue. Here, we report a case of a 50-year-old woman with a mass in the stomach found by gastroscopy. Biopsy was taken twice preoperatively under gastroscope and it was diagnosed as gastric carcinoma and neuroendocrine tumor respectively. Radical surgery was performed with gastrectomy and D2 lymph node dissection. Postoperative pathological examination finally made a definite diagnosis of gastric melanoma by immunohistochemistry. We summarize the reasons for preoperative misdiagnosis and discuss the difficulty in diagnosing gastric melanoma according to literature.

Keywords: Primary gastric malignant melanoma; extracutaneous melanoma; preoperative diagnosis.

Figure 1

Abdominal CE-CT showing large mass involving the lesser curvature of stomach.

Figure 2

Photomicrograph of postoperative specimen showing combined pattern of the tumor composing of spindled (A), epitheliod (B), and small round cells (C). Melanin pigment distributes unevenly with the tumor.

Figure 3

Photomicrograph of postoperative specimen showing strong positive for HMB-45, scattered positive for Melan-A and nests of staining of S-100.