Follicular pattern of bone marrow involvement by follicular lymphoma.

Five patterns of bone marrow infiltration by non-Hodgkin lymphoma or Hodgkin lymphoma are currently recognized, but a true follicular pattern of bone marrow involvement by follicular lymphoma has not been described. In 260 bone marrow trephine biopsy specimens involved by follicular lymphoma, we identified 12 cases with a follicular pattern of bone marrow involvement. The paratrabecular pattern was not present at all in 9, and it accounted for less than 10% of tumor burden in 3 cases. Malignant follicles in the bone marrow were similar to malignant follicles in the respective lymph nodes. Follicular dendritic cells were identified by immunohistochemical analysis. The true follicular pattern of bone marrow involvement by follicular lymphoma seems to be more frequent in women than in men. It is important to recognize this pattern of follicular lymphoma in the bone marrow because it is possible to misinterpret interstitial lymphoid aggregates as benign in the absence of the more characteristic paratrabecular pattern.