S2942 Rare Case of Primary Gastric Small Cell Carcinoma in a Renal Transplant Recipient

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INTRODUCTION: Small cell carcinoma is a rapidly progressive, poorly differentiated neuroendocrine cancer that most often originates in the lungs; however, an estimated 2.5-5% of cases originate elsewhere. Extrapulmonary small cell carcinoma (ESCC) arising from the stomach is rare. Cases occurring in renal transplant recipients are even more uncommon. Here we present a case of metastatic ESCC from a gastric primary in a renal transplant recipient. CASE DESCRIPTION/METHODS: A 52-year-old Vietnamese male presented with 1 week of epigastric pain. He had a history two renal transplantations requiring multiple thymoglobulin inductions and long-term immunosuppression. Vital signs were normal. Physical exam revealed hepatomegaly. Labs were significant for Hgb 10.0 g/dL, ALP 155 U/L, AST 71 U/L, ALT 21 U/L. CT scan of the abdomen revealed hepatomegaly, innumerable hepatic masses up to 9 cm in diameter, retroperitoneal and portal lymphadenopathy and splenic and portal varices. MRI of the abdomen revealed suspicious circumferential gastric antral wall thickening up to 2.4 cm with adjacent nodularity (Figure A). Liver core biopsy was diagnostic for metastatic small cell carcinoma. Subsequent EGD revealed a large circumferential, infiltrative, fungating and ulcerated mass in the gastric antrum (Figure B) with biopsy confirming the diagnosis of primary gastric small cell carcinoma (GSCC). The patient completed 4 cycles of palliative chemotherapy and transitioned to hospice due to lack of significant response and severe neutropenic complications. DISCUSSION: Primary GSCC are rare, representing 0.1% of extrapulmonary small cell cancers and < 0.1% of all gastric cancers. These often present with early, widespread metastasis with a 5-year survival rate of 13-20%. An increased risk of de novo cancer and gastric cancers in renal transplant recipients has been well-described, however the overwhelming majority presenting as gastric adenocarcinomas. Extrapulmonary small cell carcinomas in renal transplant patients are also rare with most cases arising from genitourinary primaries, often from the donor kidney. There are reported cases of gastrointestinal primaries from the rectum, appendix, and duodenum. To our knowledge, this represents the first reported case of metastatic GSCC in a renal transplant patient that sheds a light on the association between immunosuppression and cancer risk. The absence of well-established epidemiological data, prognostic factors and treatment guidelines necessitates reporting these rare GSCC cases.Figure 1.: Hepatic masses with 2.4cm circumferential gastric antral wall thickening (red arrow).Figure 2.: Gastric antral mass.