Primary Male Appendiceal Choriocarcinoma With Background of Low-Grade Appendiceal Mucinous Neoplasm: Diagnostic Challenges and Poor Prognosis.

Background/Aim: Choriocarcinoma is a highly aggressive trophoblastic malignancy that is most commonly gestational in origin. Non-gestational choriocarcinoma in the male gastrointestinal tract is extremely rare, and primary appendiceal involvement is exceptional. Case Report: We report such a case of a 75-year-old male who presented to the emergency room with severe abdominal pain. Physical examination indicated possible acute appendicitis suspicious for perforation, and computed tomography (CT) scans revealed a 7.5 cm mass in the lower right quadrant as well as numerous liver hypoechoic nodules. No lesions/nodules were identified in his testicles or mediastinum. Emergency surgery with right hemicolectomy and concurrent liver biopsy was performed. Pathology gross exam revealed a 7.5 cm appendiceal mass with associated appendiceal perforation. Histologically, the tumor showed a poorly differentiated carcinoma morphologically composed of syncytiotrophoblasts, cytotrophoblasts and intermediate trophoblasts with adjacent low-grade appendiceal mucinous neoplasm (LAMN). The carcinoma cells were positive for cytokeratin 7 (CK7), beta-human chorionic gonadotropin (β-hCG), GATA-binding protein 3 (GATA 3) and Sal-like protein 4 (SALL4). These features supported a primary appendiceal choriocarcinoma and the liver biopsy demonstrated metastasis of choriocarcinoma with extensive tumor necrosis. Post-surgery lab tests also revealed an exceptionally high serum β-hCG titer of 289,308 mIU/ml. The patient underwent hospice care after surgery and expired one month later. Conclusion: This is the first documented case of male primary choriocarcinoma with background of LAMN and poor prognosis. Recognition of the three carcinoma components in combination with the corresponding tumor immunohistochemical markers is the key for the precise diagnosis.