RESUMO
Follicular dendritic cell sarcoma (FDCS) is a rare neoplasm arising from lymph nodes as well as extranodal sites. Despite the characteristic histopathological features and distinctive immunophenotype, extranodal FDCS are often misdiagnosed initially as undifferentiated carcinoma, inflammatory pseudotumour, meningioma, metastatic malignant melanoma, ectopic thymoma, etc., because of its rarity and lack of awareness. Correct diagnosis of this tumour is imperative given its potential for recurrence and metastasis. We report a case of tonsillar FDCS in a 30-year-old lady who presented with slowly progressing throat pain and dysphagia for a duration of one year. Local examination showed an enlarged left tonsil with an ulceroproliferative growth. The right tonsil was normal. There was no regional lymphadenopathy. Histopathological examination of the tonsillectomy specimen showed a 2.2 x 1.5 cm infiltrative tumour composed of ovoid to spindle cells arranged in characteristic storiform, interlacing fascicular and diffuse patterns. The tumour cells were immunopositive for CD21, CD23, CD35, and S-100 protein and negative for cytokeratin. The Ki-67 antigen-labelling index (Ki-67 LI) was 6%. The EBV status was negative. It was classified as a low risk FDCS. The patient was lost to follow-up after 6 months.