Primary Diffuse Large B-Cell Lymphoma of the External Auditory Canal with Extensive Local Extension: A Case Report and Literature Review.

Introduction: Lymphoma is the second most frequent type of malignancy in the head and neck region, following squamous cell carcinoma. However, the external auditory canal (EAC) is an extremely rare primary site, with only 13 cases reported worldwide. Case Report: We present a case of middle-aged woman presented with a four-month history of swelling at the right EAC, reduced hearing, and intermittent otalgia. Over the following two months, she developed swelling at the right preauricular and cervical regions. Radiological evaluation revealed an enhancing mass at the right EAC with extensive local extension. Histopathological and immunohistochemical analyses confirmed the diagnosis of lymphoma. Determining the primary site was challenging due to the extensive involvement of multiple adjacent structures. However, we believe EAC was the most probable primary site, given that EAC swelling was the initial presenting symptom, although this cannot be established with certainty. Conclusion: The diagnosis of EAC lymphoma is challenging due to the rarity of the disease, nonspecific clinical presentation, and its frequent misdiagnosis as a benign lesion or infection at initial presentation. Additionally, obtaining an adequate biopsy sample for histopathological examination and immunohistochemical analysis can be difficult. Extensive involvement of surrounding structures at the time of presentation may further hinder accurate identification of the primary site. There is no well-established consensus on treatment guidelines, and prognosis is primarily determined by the lymphoma subtype, its clinical behaviour, the presence of B symptoms, and staging.