An overlapping case of in situ mantle cell neoplasia and leukemic non-nodal mantle cell lymphoma.

In situ mantle cell neoplasia (isMCN) and leukemic non-nodal mantle cell lymphoma (nnMCL) are classified as an indolent subtype of mantle cell lymphoma (MCL). The tumor cells of isMCN are restricted to the inner layer of the lymphoid tissue mantle zone, exhibiting an in situ pattern histologically. On the other hand, nnMCL is distributed in the peripheral blood, bone marrow and sometimes the spleen, but lymphadenopathy or systemic organ involvement is rare. We report a case of isMCN in a submandibular lymph node resected from a 65-year-old Japanese male. The tumor cells were positive for cyclin D1 (CCND1) and SOX11 expression, and were restricted to the mantle zone area of the lymph node. However, tumor cells were also detected in the stomach mucosa, bone marrow tissue and peripheral blood, suggesting nnMCL. isMCN and nnMCL may have a partly overlapping disease spectrum, although the correlation between these two subtypes has not been well described. This present case demonstrated characteristics overlapping between isMCN and nnMCL.