Evaluation of new tumors in the setting of stage I/IIA mycosis fungoides

Although mycosis fungoides is usually a slowly progressive indolent lymphoma, new cutaneous tumors might signal an aggressive phase of the disease. In order to provide appropriate therapeutic management when such tumors arise, it is important to make a correct diagnosis, which requires a bridge between clinical and histopathologic evaluations of the tumors. In this article, we describe 4 patients with preexisting diagnoses of mycosis fungoides, each of whom developed a distinct, new skin tumor. These tumors represented the following: mycosis fungoides without transformation, large-cell transformation of mycosis fungoides, lymphomatoid papulosis-associated CD30⁺ lymphoproliferative disorder arising in a patient with mycosis fungoides, and a primary cutaneous CD30⁺ lymphoproliferative disorder arising in a patient with mycosis fungoides. Each new and histologically distinct tumor was identified and treated according to a diagnosis concluded by careful clinicopathologic correlation, allowing for the selection of appropriate treatment in each case.