Enteric adenocarcinoma of the Thymus

Abstract

Abstract Introduction/Objective Thymic adenocarcinomas are extremely rare. Enteric type thymic adenocarcinoma is an even more rare subtype morphologically and immunophenotypically indistinguishable from colorectal primaries. Methods/Case Report We report a case of a 63-year-old female who presented with shortness of breath and cough. Computerized tomography (CT) scan showed an 11 x 6 cm right-sided anterior mediastinal mass extending from the great vessels to the diaphragm. Within the mass, there was a 4.8 cm possible thymic cyst that had been originally identified in 2005. Multiple right pleural and bilateral intrapulmonary nodules, and a 2 cm pericardial lymph node were also observed. A core biopsy showed a mucinous adenocarcinoma that was positive for the colorectal markers CK20, CDX2, MUC-2 and the thymic marker C-KIT, and negative for CD5, PAX8, CK7, TTF-1, and ER immunostains. The tumor was negative for PDL1 22c3 (CPS<1) and positive for TROP2. PET-CT did not reveal any other primary. A diagnosis of enteric adenocarcinoma of the thymus Masaoka stage IV was established and the patient is scheduled to receive chemotherapy. Genomic testing is pending to guide potential targeted therapy. Results (if a Case Study enter NA) NA Conclusion A recent compilation of 29 cases mostly from the literature described aggressive clinical behavior, high association with thymic cysts, and coexpression of CD117 and enteric markers similar to this case. All patients had poor response to conventional platinum-taxanes regimens. Two patients received targeted therapy without benefit. None of these patient received colorectal type regimens. Although the number of reported cases is still very small, these results suggest that optimal therapy for these aggressive tumors has yet to be defined.