Lichen sclerosus mimicking mycosis fungoides preceding B-cell lymphoma - diagnostic challenges

Introduction: The diagnosis of cutaneous lymphomas is extremely difficult because of their morphological diversity and clinical similarity to many dermatoses. Objective: Presentation of the case of a 70-year-old woman diagnosed with lichen sclerosus in whom the evolution of skin lesions raised suspicions of lymphocytic hyperplasia. Case report: The patient diagnosed with lichen sclerosus was hospitalized three times due to exacerbation of skin lesions with accompanying mycosis fungoides-mimicking infiltration. Cutaneous lymphoma was excluded in biopsy specimens collected from skin lesions. In the following months, a new nodular lesion appeared on the patient’s face that turned out to be marginal zone lymphoma. After increasing the dose of methotrexate to 20 mg/week, a rapid remission of skin lesions was achieved. Conclusions: The presented case shows that the diagnosis of primary cutaneous lymphoma is a significant challenge in everyday dermatological practice and requires repeated biopsy.