Bone marrow involvement by non-Hodgkin's lymphom.

We retrospectively studied 156 patients with non-Hodgkin's; ymphoma (NHL) in order to evaluate the incidence of bone marrow (BM) involvement at the time of diagnosis. The incidence of marrow involvement in NHL was 35% (55 patients). The most common histologic type of lymphoma was diffuse large cell lymphoma with 30% of the cases having bone marrow involvement. The highest incidence of marrow involvement was seen in immunoblastic lymphoma & the lowest incidence in diffuse mixed cell lymphoma. Bone marrow lymphoma was present in 50% of low-, 34% of intermediate-, and 55% of high-grade lymphomas. B-cell vs T-cell lymphoma in cases of marrow involvement was 56% to 42%. The most frequent pattern of marrow involvement was interstitial & diffuse (56% & 31%). The paratrabecular pattern was rare (4%). Most lymphomas (42%) extensively involved marrow space greater than 76% of the total marrow space. Discordant histology between lymph node and BM was seen in 10 cases (18%). Biopsy was the best method compared to smear & clot section (sensitivity 82% vs 72% vs 69%). In conclusion, our study revealed that the most common histologic type of marrow lymphoma was diffuse large cell type with frequent interstitial and diffuse pattern and extensive involvement of the marrow space. No predilection for a trabecular pattern was found. This result was in contrast to that in the Western literature.