Leukemic Non-nodal Mantle Cell Lymphoma: Diagnosis and Treatment.

OPINION STATEMENT: Mantle cell lymphoma (MCL) encompasses nearly 6% of all the non-Hodgkin lymphomas. It is considered an incurable neoplastic process arising from B cells. The cytogenetic abnormality t(11;14) (q13; q32) leading to cyclin D1 overexpression is the sentinel genetic event and provides an exceptional marker for diagnosis. MCL is generally considered to have an aggressive course as compared with other indolent lymphomas with traditionally reported median survival of 3-5 years. According to the 2016 WHO classification, there are two major known variants of MCL: classical which affects the lymph nodes and extra nodal sites and leukemic non-nodal MCL (L-NN-MCL) which characteristically involves the bone marrow, peripheral blood, and the spleen. It is important to distinguish between classical and leukemic non-nodal MCL since the latter variant of MCL follows a rather indolent course with a wait and watch approach in order to avoid overtreatment. However, a subset of patients with L-NN-MCL can transform into a more aggressive course requiring treatment. Current evidence suggests those patients with alteration in TP53 gene do not respond to standard chemotherapy agents and may need targeted therapy. In this review, we describe the characteristics of L-NN-MCL, its diagnosis, and management.