Synchronous adenocarcinoma and follicular lymphoma of the stomach.

A 73-year-old Japanese man with synchronous follicular lymphoma and adenocarcinoma of the stomach underwent curative surgical resection. The follicular lymphoma lesion was preoperatively diagnosed as extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) according to biopsy samples. However, postoperative pathological evaluations revealed components of CD10-positive and CD10-negative lymphoma cells within the lymphoma lesion. This case highlights the potential difficulty of diagnosing gastric follicular lymphoma. In such cases, conducting repeat pathological examinations of biopsy samples or resected specimens is required to obtain a correct diagnosis of follicular lymphoma.