CD5-Positive Low grade Follicular Lymphoma Involving the Bone Marrow

Lessons From the Friday Unknowns

Sections show bone core biopsy with marrow occupied by a diffuse, focally nodular small lymphocytic infiiltrate. Single area shows increased large cells, less than 15 per high power field, where Ki67 reaches ~60% (focal).

CD3: Numerous small lymphocytes in the background are positive
CD5: Numerous small lymphocytes in the background are positive
CD10: Multiple clusters of lymphocytes are highlighted (follicular pattern)
CD20: Most lymphocytes are positive
CD21: Focal follicular dendritic cell meshworks are highlighted
CD43: Numerous small lymphocytes in the background are positive
BCL2: Most lymphocytes are highlighted. Coexpression with BCL6, CD10 and CD20.
BCL6: Multiple clusters of lymphocytes are highlighted (follicular pattern)
Cyclin D1: negative
Ki67: Overall <10% proliferation rate of the affected bone. Focal area shows ~60% proliferation rate.
LEF1: Scattered small lymphocytes are positive

CD20

CD5

BCL2

Ki67

CD10

Link to digital slides: bit.ly/3aDM5ht|Case 5

Further Read:

Follicular pattern of bone marrow involvement by follicular lymphoma - PubMed