Mantle cell lymphoma. Morphologic findings in bone marrow involvement.

Although mantle cell lymphoma (MCL), has been well described in lymph nodes, involvement of blood and bone marrow has not been well defined. The authors reviewed involved blood and marrow specimens from 13 patients with MCL to determine patterns of infiltration. These findings were compared to marrow involvement by follicular small cleaved cell lymphoma (SCCL) and small lymphocytic lymphoma (SLL). Peripheral blood involvement by MCL was present in 5 patients (38%). The circulating lymphoma cells were small (7-10 mu) with slightly folded nuclei. Marrow involvement ranged from 5% to 90% of the marrow space and was predominantly intertrabecular, including nodules and interstitial infiltrates (9 cases each; 68%). Paratrabecular aggregates (6 cases; 46%) and diffuse replacement by lymphoma (3 cases; 23%) were also seen. In SCCL, paratrabecular involvement was seen as were interstitial nodules. Cases of SLL showed diffuse, interstitial or nodular involvement without paratrabecular localization. Cytologic comparison showed nuclei that were angulated in SCCL, round in SLL, and slightly irregular in MCL, with considerable overlap among the groups. The architectural and cytologic findings in marrow involved by MCL show features of both SCCL and SLL, and cannot be used to definitively diagnose MCL.