Primary cutaneous peripheral T-cell lymphoma with a late relapse solely in the ileum mimicking monomorphic epitheliotropic intestinal T-cell lymphoma

Background

Primary cutaneous peripheral T-cell lymphomas (PC-PTCLs) are classified into mycosis fungoides (MF) and other rare specific types; and those do not fit into any specific entities are designated as PTCL, not otherwise specified (NOS), an aggressive neoplasm. Monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL) is an aggressive primary intestinal T-cell lymphoma with enteropathy in the non-neoplastic mucosa. We report a rare case of PC-PTCL-NOS with a late relapse solely in the ileum after complete remission. We discuss the importance of evaluating enteropathy, megakaryocyte-associated tyrosine kinase (MATK) immunostaining, and the implication of clonal relationship of metachronous lymphomas.

Case report

We reviewed the histopathology and immunohistochemistry of the skin tumor from a 68-year-old female and the relapsed intestinal T-cell lymphoma. The tumor cells “trans-regressed” from large and pleomorphic in the skin to small/medium-sized cells with clear cytoplasm in the ileum; and furthermore, there was immunophenotypic alteration. However, there was no enteropathy in the non-tumoral ileal mucosa adjacent to the tumor proper and both the cutaneous and ileal tumors were negative for MATK. Clonality study showed clonal TRG and TRB rearrangement with identical band sizes of the amplicons, confirming primary cutaneous tumor with a late relapse in the ileum.

Conclusions

Although PC-PTCL-NOS is an aggressive neoplasm, rare cases such as this might have a long-term survival. Furthermore, the late relapse mimicking MEITL is intriguing and exceptional, in spite the fact that MEITL is a primary intestinal T-cell lymphoma with a typical histopathology and immunophenotype. Detailed clinicopathological and molecular studies are mandatory to elucidate the clonal relationship of metachronous lymphomas, as this has important clinical implication for treatment. Evaluation of the non-tumoral intestinal mucosa for enteropathy and immunostaining for MATK might help to differentiate a mimicker from a true MEITL.