Rationale: Mycosis fungoides (MF) is the most common primary cutaneous T-cell lymphoma, yet palmar MF is extremely rare and easily mistaken for chronic dermatoses such as psoriasis. Delayed recognition can lead to inappropriate treatment and worse outcomes. This case demonstrates how careful histopathology and immunohistochemistry can provide critical diagnostic clarity in atypical presentations. Patient concerns: A 63-year-old woman presented with an 8-year history of erythema, dryness, scaling, and fissuring on both palms. The lesions had been misdiagnosed as psoriasis and showed no response to long-term topical calcipotriol. Diagnoses: Histopathology of a palm biopsy revealed epidermotropism of atypical lymphocytes with cerebriform nuclei and Pautrier microabscesses. Immunohistochemistry demonstrated positivity for CD2, CD3, CD4, and CD45RO with immunophenotypic variation, confirming palmar MF. The patient was staged as early MF (IA–IB). Interventions: Systemic therapy with intramuscular interferon α-2b, oral methylprednisolone, and acitretin was initiated due to chronicity, bilateral palm involvement, and resistance to topical therapy. Outcomes: Significant improvement was noted after 2 months. At the 1-year follow-up, her palms showed complete clearance of lesions with sustained remission. Lessons: This case highlights the diagnostic pitfalls of palmar MF and underscores the necessity of early biopsy in patients with persistent, treatment-resistant palm dermatoses. Raising clinical awareness of this rare entity may prevent misdiagnosis, facilitate timely therapy, and ultimately improve patient prognosis.
Zhao et al. (Fri,) studied this question.