Abstract

We report a case of a 68-year-old Caucasian male with a two-year history of Stage IIA mycosis fungoides and new onset of heme-crusted, pruritic, pink papules at his bilateral thighs without associated systemic symptoms. The patient was undergoing management of the cutaneous lymphoma with oral acitretin. Tangential shave biopsy and histopathologic analysis of the patient’s new skin lesions demonstrated a diffuse atypical lymphocytic infiltrate with epidermotropism, larger cells with CD30 positivity, and clonal populations on T-cell receptor rearrangement studies. The clinical and histopathologic findings confirmed a diagnosis of large cell transformation of mycosis fungoides, and the patient underwent staging with PET/CT and bone marrow biopsy which were negative for systemic T-cell lymphoma involvement. The patient was initiated on six cycles of brentuximab with clinical improvement of his cutaneous mycosis fungoides. Large cell transformation of mycosis fungoides can occur in up to 50% of advanced mycosis fungoides (Stage IIB or greater) and has been associated with a poorer prognosis. In addition, upwards of 90% of cases of large cell transformation are diagnosed in the advanced stages of mycosis fungoides. A diagnosis of focal large cell transformation in early-stage mycosis fungoides (Stage IA to Stage IIA) is rare, but often necessitates aggressive therapy, such as in our patient’s case. Dermatopathologists should be aware of the histopathologic findings and significance of large cell transformation of mycosis fungoides to facilitate early diagnosis and treatment of this condition.

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