High Grade B-Cell Lymphoma, Double Expressor

Lessons From the Friday Unknowns

Histologic sections show fragments of bone and bone marrow tissue involved by a malignant neoplasm.

The neoplasm is composed predominantly medium-sized lymphoid cells with relatively dispersed chromatin, many with blastoid appearance. Apoptotic bodies are easily identified. No areas of overt necrosis are seen. A few small foci show bone marrow elements with trilineage.

By immunohistochemistry, the neoplastic cells are positive for CD20, PAX5, MUM1 (~95%), BCL6 (~90%), BCL2 (~90%) and MYC (~50%). They are negative for CD3, CD10, CD21, CD138, cyclin D1, SOX11, TdT and CD34. A subset of the tumor cells appears to be weakly positive for CD5. The proliferation index measured by Ki-67 is approximately 90% in the tumor cells. CD3 and CD5 highlight T cells in the background. CD138 highlights plasma cells, which show no definite clonality demonstrated by kappa and lambda immunostains. In situ hybridization for Epstein-Barr virus-encoded small RNA (EBER) is negative.

Link to digital slides: https://bit.ly/3eSyhlz ~ Case 3