Symptomatic Thyroglossal Duct Cyst Presenting With Synchronous and Localized Tongue Base Extranodal Mantle Cell Lymphoma. A Unique Case Report Demonstrating Lymphoma Colonization of Cyst Wall, Potentially Relating to a Persistent Embryological Foramen Cecum Remnant

A 77-year-old male presented with a progressively enlarging midline neck mass. On further investigation he was found to have synchronous thyroglossal duct cyst and extranodal mantle cell lymphoma (MCL) localized to the base of tongue. Both pathologies were managed simultaneously with a surgical approach and the patient remained in clinical remission at the time of publication without indication for systemic oncological treatment. Histology revealed primary extranodal nonblastoid MCL forming a base of tongue mass, with colonization of the thyroglossal duct cyst. Lymphoma was also found in the epithelium of a crypt-like tract traversing one of the tongue base tumor sections. This tract was anatomically and histologically consistent with documented descriptions of the foramen cecum. This case report illustrates a previously undescribed temporal, clinical, and histological association between a base of tongue MCL and symptomatic thyroglossal duct cyst. We provide evidence for a potential causal relationship for the presentation of the thyroglossal duct cyst as a result of oropharyngeal MCL, in the absence of clinical and histological evidence of disseminated disease, directly infiltrating from its tongue base origin to the infrahyoid neck region, potentially via an embryologic foramen cecum remnant. We also highlight the crucial role of the histopathologist in multidisciplinary clinicopathological discussion in demonstrating how fundamental embryological and microanatomical relationships can unite apparently separate diseases.