Mantle cell lymphoma with partial involvement of the mantle zone: an early infiltration pattern of mantle cell lymphoma?

Most patients with mantle cell lymphoma present with a diffuse or nodular infiltration of the involved organs at diagnosis. We present two patients with a rare morphological variant, displaying a partial involvement of the mantle zone. Patient 1 presented with an enlarged inguinal lymph node, which showed marked follicular hyperplasia with singly spread Cyclin D1+ small lymphoid cells in the mantle zones. An additional lymph node biopsy taken 3 months later showed the same pattern. Patient 2 presented with a classical mantle cell lymphoma with lymph node, bone marrow and gastro-intestinal involvement. However, revision of an appendectomy specimen taken 4 years earlier showed pronounced follicular hyperplasia with singly spread Cyclin D1+ small lymphoid cells in the mantle zones. Mantle cell lymphoma with partial involvement of the mantle zone has rarely been reported and many represent an early manifestation of mantle cell lymphoma. Our cases also illustrate that the inclusion of an anti-cyclin D1 antibody in the diagnostic panel of antibodies to study unexplained follicular hyperplasia, might be advised.