Publication:

Persistence pays: a case of primary cutaneous B-cell lymphoma masked by granulomas

Primary cutaneous diffuse large B cell lymphoma is a form of cutaneous lymphoma characterized by a clonal proliferation of B cells that is often presents with a delayed diagnosis, and therefore often carries poor prognosis. We report a 77-year-old female presenting with a shin lesion resembling a deep dermal or fungal process. Initial biopsy revealed superficial and deep mixed granulomatous inflammatory infiltrate, which suggested an initial diagnosis of Majocchi’s granuloma, despite negative fungal cultures. Despite treatment, the progressive worsening of the skin lesions prompted multiple repeat biopsies, which eventually revealed CD20, Bcl-2, and Bcl-6 staining, loss of CD3 and CD30, and high Ki67, compatible with a cutaneous high-grade B-cell lymphoma. Clinical presentations of primary cutaneous diffuse large B cell lymphoma can mimic several different clinical entities, rarely including granulomatous disease, such as a fungal pathology. This report highlights the importance of persistence and a multimodal approach to the diagnosis of unidentified skin lesions, especially in the setting of failure to respond to standard therapies.