Primary Tonsillar Epithelioid Follicular Dendritic Cell Sarcoma: Report of a Rare Case Mimicking Undifferentiated Carcinoma and a Brief Review of the Literature

Abstract

We present a 52 years old male with a left tonsillar follicular dendritic cell sarcoma with prominent epithelioid features that on light microscopical examination bore a striking resemblance to a lymphoepithelial or undifferentiated carcinoma. The tumor was immunohistochemically positive for CD21 and CD35 and negative for cytokeratins. Two distinct histopathological features (both present in our case) that may serve as clues to the correct diagnosis on light microscopical examination were formation of ectatic pseudovascular spaces lined by malignant cells and the presence of non-neoplastic multinucleated giant cells. Familiarity with the above-mentioned morphological clues, and awareness that this tumour may occur in anatomical sites outside the lymph node, are essential for accurate diagnosis.

Keywords: Carcinoma; Dendritic cell sarcoma; Follicular; Oropharynx; Palatine tonsil.

Fig. 1

a The tumor was predominantly composed of syncytial sheets of atypical epithelioid-appearing cells amidst a lymphocyte-rich background. Hematoxylin and Eosin stain, × 100 magnification. b The tumor cells exhibited enlarged nuclei, marked nuclear membrane irregularity, vesicular chromatin, and occasional discrete single nucleolus, Hematoxylin and Eosin stain, × 400 magnification. c In some areas, the tumor cells displayed a spindled morphology and were arranged in vague fascicles. Hematoxylin and Eosin stain, × 100 magnification. d On close inspection several foci contained scattered multinucleated giant cells. Hematoxylin and Eosin stain, × 400 magnification. e Occasional significantly dilated ectatic pseudo-vascular spaces lined by tumor cells were also present. Hematoxylin and Eosin stain, × 40 magnification

Fig. 2

a The tumour cells diffusely expressed CD21. Immunohistochemistry, CD21 antibody, × 20 magnification. b The tumour cells diffusely expressed CD35. Immunohistochemistry, CD35 antibody, × 40 magnification