Lymphomatoid papulosis followed by anaplastic large cell lymphoma in a pediatric patient.

Lymphomatoid papulosis (LyP) is a benign, self-healing, papular eruption that can wax and wane over time. Transformation to T-cell lymphoma has been well documented in 10% to 20% of adults with LyP. However, this transformation rarely occurs in patients younger than 20 years of age. Here, we present the first known pediatric patient in Korea, a 12-year-old boy who developed a subcutaneous nodule on the scrotum 13 months after papulonecrotic lesions of LyP were identified on both lower extremities and face. Histological and immunohistochemical examination of the subcutaneous nodule revealed anaplastic large cell lymphoma (ALCL). A T-cell receptor gene rearrangement analysis demonstrated an identical rearranged pattern in the two specimens, indicating that a common T-cell clone had proliferated over time in both the LyP and ALCL lesions.