A263 MALIGNANT MELANOMA OF UNKNOWN PRIMARY WITH GASTRIC AND DUODENAL METASTASES: A CASE REPORT

This abstract presents a case of malignant melanoma of unknown with primary biopsy-proven gastric & duodenal metastases. Retrospective chart review report. This case report presents a 65-year-old male with a distant history of melanoma of the upper abdominal cutaneous surface. He underwent a successful wide-margin excision & a right sentinel axillary lymph node, which showed a 4mm focus. A follow-up right axillary lymph node dissection removed 5 melanoma-negative lymph nodes. Given these results, he was discharged by his oncologist and continued to have ongoing cutaneous surveillance by a dermatologist. The patient then presented with progressive fatigue, pre-syncope, dyspnea and was found to have a normocytic anemia with a Hgb of 75 g/L. His last Hgb was measured at 151 g/L three months prior on routine bloodwork. All of this occurred in the absence of any overt G.I. bleeding, abdominal pain or any other G.I. symptom, nor was there evidence of any cutaneous recurrence of his melanoma. Furthermore, the patient had a normal EGD and colonoscopy 9 months and 3 years prior, respectively. Gastroenterology was consulted for endoscopic evaluation of a possible G.I. source for his anemia. EGD showed multiple dark, flat 1mm lesions along the greater curvature of the stomach, which were biopsied, and multiple similar lesions found in the D1 & D2 segments of his duodenum (figure 1). Biopsy results were positive for metastatic malignant melanoma. Subsequent PET scan identified multiple metastases in the liver (the largest measuring 4.7cm) and diffuse uptake in the skeletal marrow suggesting malignant marrow infiltration. Bone marrow biopsy confirmed this with metastatic melanoma accounting for 70% of bone marrow cellularity. Oncology referral was made for chemotherapy initiation. Malignant melanoma is a rare tumor accounting for 1–3% of all tumors. It has been observed to have GIT (GI tract) metastases in up to 50–60% of cases. However, due to being largely asymptomatic, GIT metastases are mainly diagnosed post-mortem on autopsy. Only 1–5% of all cases are diagnosed in the ante-mortem period. Furthermore, when GIT metastases are present there are often metastases to other visceral organs, and the median survival time for patients with GIT metastases is less than 1 year. Collectively, this case highlights the potential utility for interval endoscopic surveillance in patients with a history of treated cutaneous melanoma and absence of identifiable cutaneous recurrence. Recent evidence has shown that endoscopic evaluation and diagnoses is more reliable than traditional radiographic identification of gastric metastases. Moreover, endoscopic evaluation allows for direct visualization of the gastric mucosa, direct biopsy of any identified lesions to obtain a pathologic diagnosis, and assessment of response to chemotherapy. None

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