Diagnosis: Mycosis fungoides
Following the biopsy of her right cheek, a histopathologic analysis demonstrated an atypical lymphocytic infiltrate positive for CD3 and CD4. These histopathologic features led to a diagnosis of recurrent mycosis fungoides (MF), a type of cutaneous lymphoma. (Our patient’s cutaneous lymphoma had been in remission for a year following local radiotherapy.)
MF is the most common type of cutaneous lymphoma, with an incidence of 6.4 to 9.6 cases per million people in the United States.1 There are also 2 rare subtypes of MF: the psoriasiform and palmoplantar forms. Psoriasiform MF presents with psoriasis-like plaques, while palmoplantar MF initially presents on the palms and soles.
Patients with classic MF typically present with patches and plaques—with the late evolution of tumors—on non–sun-exposed areas.1 Our patient’s clinical presentation was atypical because the rash manifested on a sun-exposed area of her body.
MF and other cutaneous lymphomas should always be part of the differential diagnosis for an unexplained persistent rash, especially in a patient with a history of MF. The development of lymphomas is thought to be a stepwise process through which chronic antigenic stimulation results in an accumulation of genetic mutations that then cause cells to undergo clonal expansion and, ultimately, malignant transformation. Genetic, environmental, and immunologic factors that contribute to the disease pathogenesis have been identified.2
Once clinical features point toward MF, the diagnosis can be further differentiated from other benign inflammatory mimics with a biopsy demonstrating cerebriform lymphocytes homing toward the epidermis, monoclonal expansion of T cells, and defective apoptosis.3
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