Abstract

We report a case of a 66-year-old woman who presented with hyperpigmented papules scattered on the trunk and an erythematous papule on the left ventral forearm. The forearm lesion was biopsied and microscopic examination revealed marked epidermal spongiosis, lymphocytic exocytosis, and prominent intraepidermal atypical lymphocytes. A biphasic population of lymphocytes was noted with larger and smaller cells in the epidermis and scattered larger cells in the dermis. Immunohistochemical stains highlighted the epidermal and dermal CD3, CD4, and CD8 positive T-cells. The atypical intraepidermal T-cells and scattered larger dermal T-cells were positive for CD30 and CD3, and were predominantly CD8 positive, with rare possible cells staining for CD4. Overall, the combined histologic and clinical features favor a diagnosis of an uncommon variant of lymphomatoid papulosis (LyP) with DUSP22-IRF4 rearrangement with prominent spongiosis. The differential diagnosis includes mycosis fungoides, anaplastic large cell lymphoma, and reactive conditions like CD30 positive lymphomatoid drug reactions. This is an unusual case of a rare entity with marked spongiosis, mimicking acute spongiotic dermatitis histologically, that highlights the importance of clinicopathologic correlation in arriving at a correct diagnosis.