Double trouble: insights from a rare case of extranodal composite lymphoma in an elderly man, with comprehensive literature review.

Composite lymphoma (CL) is a rare cancer characterized by the concurrent occurrence of more than one type of lymphoma within the same organ or tissue in an individual. Its occurrence at extranodal sites is exceptional, with only a few cases documented in the literature. A 62-year-old gentleman presented with dystonia, dysphagia, and irregular enlargement of the right tonsil for the last three months. Based on a clinical suspicion of tonsillar malignancy, tonsillectomy was done. The histopathologic examination revealed effacement of the architecture by large irregular lymphoid nodules with interfollicular expansion. The nodules showed sheets of small atypical lymphoid cells, while the interfollicular areas showed large atypical lymphoid cells with scattered typical binucleate Reed-Sternberg cells. Immunohistochemistry confirmed mantle cell lymphoma (MCL) in the nodules and classical HL (cHL) in the interfollicular areas. Based on these features, a diagnosis of composite MCL with cHL was rendered. He was treated with bendamustine and rituximab chemotherapy and remained in complete remission for five years when he presented with significant right-sided neck swelling. Percutaneous fine needle aspiration and subsequent flow cytometry confirmed a relapse of the MCL component of the CL. The index report documents an exceptional case of CL, comprising MCL and cHL, presenting at an uncommon extranodal site. In addition, it also emphasizes the importance of adequate sampling and the simultaneous use of immunochemistry and/or flow cytometry to confirm the presence of more than a single type of lymphoma, which may be easily overlooked on microscopy alone.