Hidden Identity: Unmasking Follicular Dendritic Cell Sarcoma Mimicking Squamous Cell Carcinoma

Abstract Background: We present the case of a 55-year-old male with progressive dysphagia and weight loss. CT neck revealed a large oropharyngeal lesion infiltrating the right tonsil, uvula, and soft palate. Initial biopsy and later excision specimens were examined. Aims: To diagnose and understand the rare presentation of Follicular Dendritic Cell Sarcoma (FDCS) in the tonsils and emphasize the importance of considering FDCS in the differential diagnosis. Materials and Methods: Biopsy and excision specimens were analysed for histopathological features. Immunohistochemistry was employed to confirm the diagnosis. Results: Histopathology revealed ulcerated squamous epithelium overlaying a tumour with epithelioid and spindle-shaped cells, multinucleate forms, and extensive necrosis. Immunohistochemistry confirmed CD21 and CD23 positivity. Conclusions: Our case underscores the need to consider rare entities like FDCS when encountering tonsillar neoplasms. Initial tests using epithelial markers were inconclusive, leading to the consideration of FDCS. Our findings contribute to the growing body of literature on extranodal FDCS and its diagnostic challenges. Keywords: Follicular Dendritic Cell Sarcoma, Immunohistochemistry, Oropharyngeal lesion, Tonsillar neoplasm.