Follicular Helper T-Cell Lymphoma

Lessons From the Friday Unknowns

Sections of the needle biopsies of left retroperitoneal lymph node reveal a diffuse, abnormal lymphohistiocytic proliferation, with effacement the normal lymph node. The lymphocytes are a mixed population of small, intermediate size and large cells, with predominance of intermediate sized cells. The lymphocytes are atypical, having angulated nuclei with irregular nuclear contours and a hyperchromatic nuclear staining pattern. Histiocytes are uniformly present in high number within the lymphomatous proliferation. A moderate small vascular proliferation is present.

Submitted immunoperoxidase-stained sections show positive immunoperoxidase staining of atypical lymphocytes for CD3, CD5, CD4, ICOS, PD-1 (weak), CXCL-13 and BCL-6, with non-immunoreactivity of atypical lymphocytes for CD7, CD8, CD20 and CD10. Approximately 30% of atypical lymphocytes show weakly positive immunostaining for CD30. Extra follicular meshworks of CD21 and CD23 positive follicular dendritic cells are not definitively detected. Approximately 70% of atypical lymphocytes show positive immunostaining for Ki-67. In situ hybridization for EBV (EBER) is negative.