Angioimmunoblastic T-Cell Lymphoma

Lessons From the Friday Unknowns

Histologic sections show a large lymph node that is almost completely replaced by lymphoma. Scattered reactive follicles are present surrounded by the neoplasm. The neoplasm is composed predominantly of intermediate-size cells with abundant pale cytoplasm. Some high endothelial vessel proliferation is present. Eosinophils and plasma cells are rare.

The neoplastic cells are positive for CD3, CD4, CD5, CD7, CD30 (subset, 10–20%), PD1, ICOS, CXCL13, BCL–6 (subset), BCL–2 and cyclin D1 (small subset, <5%), and are negative for CD8, CD10, CD20, CD21, CD23, CD56 and PAX-5. The antibody specific for Ki-67 shows a proliferation rate of approximately 60–70%. The antibody specific for CD21 and CD23 show some disordered networks of follicular dendritic cells.

Rare small cells are positive but most likely represent bystander benign lymphocytes. The neoplastic cells are negative for EBER.