Tonsillar Leishmaniasis: A Rare Clinical Entity Mimicking Malignancy in the Oropharynx - A Case Series from Northeastern Italy.

Purpose: Tegumentary leishmaniasis (TL) is a neglected disease in Europe, often underdiagnosed or misdiagnosed due to its variable clinical presentation. Mucosal leishmaniasis (ML) is a rare manifestation of TL, and isolated tonsillar leishmaniasis is an even rarer finding, with very few reported cases. This study aims to expand knowledge on this unusual clinical entity by describing five cases of isolated tonsillar leishmaniasis diagnosed in the Emilia-Romagna region (ERR), northeastern Italy, emphasizing diagnostic challenges and treatment outcomes.

Methods: Between January 2014 and December 2024, all consecutive patients presenting with unilateral tonsillar swelling and pharyngodynia were evaluated at otolaryngology units in ERR hospitals. Histopathological analysis, special stains (H&E, Giemsa, PAS, Ziehl-Neelsen), and immunostaining (CD1a) were performed at the referring hospital. Microbiological confirmation was obtained through real-time PCR targeting Leishmania kDNA and rRNA. Treatment was administered according to current TL guidelines.

Results: We included five patients who presented with unilateral tonsillar swelling mimicking malignancy and with a histological diagnosis of non-necrotizing granulomas. Histology revealed amastigotes in four cases. PCR confirmed Leishmania infection in all cases. Treatment with liposomal amphotericin B or pentamidine led to complete clinical remission.

Conclusion: Isolated tonsillar leishmaniasis should be considered in the differential diagnosis of head and neck tumors, especially in endemic regions. Histological and molecular tools are essential for accurate diagnosis. Increased awareness among clinicians and pathologists is necessary to improve recognition and management of this rare presentation.