Primary cutaneous anaplastic large cell lymphoma (PC-ALCL) is a rare CD30-positive T-cell lymphoproliferative disorder (TCLPD) that can present diagnostic and management challenges, particularly when overlapping with other CD30+ entities such as lymphomatoid papulosis (LyP) and mycosis fungoides (MF). We present the case of a 44-year-old man with a 4-year history of waxing and waning erythematous lesions on the buttocks and thigh. Biopsy of the left buttock lesion revealed CD30+ ALK-negative anaplastic large cell lymphoma, while the contralateral thigh lesion was consistent with eczema. PET/CT demonstrated a solitary hypermetabolic right external iliac node, and biopsy confirmed focal CD30-positive TCLPD with T-cell immunophenotype (CD2+, CD4+, CD5dim+, CD30+, loss of CD3 and CD7). No systemic B symptoms or additional disease burden were identified.
This presentation highlights the diagnostic complexity of differentiating PC-ALCL from systemic ALCL with secondary skin involvement, given the waxing and waning cutaneous lesions suggestive of LyP, and the erythematous thigh patch raising concern for MF. Accurate subclassification is essential, as prognosis and therapeutic approaches differ substantially. Localized PC-ALCL is often indolent with excellent outcomes following targeted approaches such as topical steroids or radiotherapy, whereas systemic ALCL requires multiagent chemotherapy or targeted therapy. The advent of brentuximab vedotin, an anti-CD30 antibody-drug conjugate, offers an effective, less toxic option for refractory or multifocal disease.
This case underscores the importance of clinicopathologic correlation, thorough staging, and multidisciplinary review in the evaluation of CD30-positive TCLPDs. Early recognition of overlapping disease processes enables tailored management strategies to optimize patient outcomes.
