Localized Tonsillar Amyloidosis Associated With a Plasma Cell Neoplasm Presenting as an Oropharyngeal Mass: A Diagnostic Challenge.

Amyloidosis is a rare and heterogeneous group of disorders characterized by extracellular deposition of misfolded proteins, which may present as either localized or systemic disease. In the head and neck region, the presentation of amyloidosis is uncommon and may clinically mimic neoplastic processes. We report the case of a 58-year-old man with a five-year history of progressive oropharyngeal symptoms, initially perceived as a foreign body sensation and intermittent odynophagia, later evolving to dysphagia to solids. Physical examination revealed marked asymmetry of the palatine tonsils due to a mass originating from the left tonsillar fossa. Imaging studies confirmed a well-defined lesion without clear signs of invasion. Given the progressive symptoms and the size of the lesion, surgical excision was performed. Histopathological analysis demonstrated amyloid deposition confirmed by Congo red staining, with immunophenotypic features consistent with a lambda-restricted plasma cell neoplasm. The patient was referred for further hematologic evaluation to exclude systemic disease, but declined additional workup. This case illustrates how localized amyloidosis may closely resemble neoplastic disease both clinically and radiologically, and highlights the central role of histopathological evaluation. It also emphasizes the importance of considering systemic involvement even in apparently localized presentations.