Metastatic Gastric Melanoma Masquerading As Bleeding Ulcer: A Challenging Case Of Rarity

The most common cause of death secondary to melanoma is widespread metastasis. Malignant melanomas appear to have a particular tendency of metastases to the gut. However, these metastases rarely involve the gastric mucosa of the stomach. We present a case of 68-year-old male with a past medical history of cutaneous melanoma 3 years prior treated with wide excision and no evidence of metastasis at the time, presented with complaints of a one-month history of nausea, dizziness, black stool and a 15-lb weight loss. Initial workup revealed a Hemoglobin 9.4 g/dl (reduced from his baseline of 14g/dl) and positive occult blood in the stool. Physical exam was benign otherwise. Given the presentation of anemia, melena and weight loss, the patient underwent esophagogastroduodenoscopy (EGD), which revealed diffuse mild gastropathy, three large ulcerative gastric polyps about 3-4 cm, and several smaller gastric polyps [Image 1]. Biopsy revealed metastatic gastric melanoma with staining positive for S100+, SOX 10+, MART1+, AMB45 +, and BRAF + [Image 2,3]. CT (Computed Tomography) of the chest and abdomen, revealed lesions affecting the lung and liver. The patient was diagnosed with Stage 4 metastatic melanoma. Chemo and radiation therapy were started, however, he was soon changed to hospice care and died within 4 months of diagnosis. Melanoma can metastasize to the gastrointestinal tract. Studies report up to 60% pathological involvement of the gastrointestinal tract in autopsies of patients with metastatic melanoma. However, rarely do these metastases involve the gastric mucosa of the stomach, only reaching clinical relevance in a median of 2% of patients with metastatic melanoma (range: 0.8-8.9%). Gastric manifestations are non-specific and may present as obstruction, gastrointestinal hemorrhage, anemia, weight loss, or abdominal pain. Non-specific pulmonary, hepatic, or GI symptoms in conjunction with the history of melanoma should raise the suspicion of metastases. Management includes surgical and non-surgical interventions, including, chemotherapy and palliative radiation therapy (XRT). Metastatic gastric melanoma should be considered when evaluating a patient with melanoma, especially in those who manifest with nonspecific GI symptoms. Identification of metastases early on can better guide therapeutic treatment recommendations and improve patient outcomes.2644_A Figure 1. Esophagogastroduodenoscopy (EGD) revealed diffuse mild gastropathy, th ree large ulcerative gastric polyps about 3-4 cm, and several smaller gastric polyps.2644_B Figure 2. Diffuse S100 + staining in the tumor cells supporting the diagnosis of melanoma.2644_C Figure 3. H&E stained section shows gastric mucosa being replaced by tumor. The tumor is growing in a diffuse fashion. It is comprised of cells with round, oval and spindled nuclei. There is a moderate amount of amphophilic to eosinophilic cytoplasm. Mitotic figures are easily identified.