Primary Cutaneous Large B-Cell Lymphoma, Leg Type, Localized on the Dorsum.

Primary cutaneous large B-cell lymphoma, leg-type (PCLBCL-LT), is a large B-cell lymphoma primarily involving the skin. It is distinguished from the other 3 subsets of this lymphoproliferative disorder by its immunohistopathological features, configuring confluent sheets of medium-sized to large B lymphocytes with round nuclei provided with evident nucleoli, resembling centroblasts or immunoblasts, which express Bcl-6, Bcl-2. Prevalently appearing on the lower limbs, as a single or multicentric and frequently ulcerated skin nodule or plaque, PCLBCL-LT has a worse prognosis than the other large B-cell lymphomas. Moreover, the age of onset is delayed (7th decade) compared to those of the other 3 subtypes (6th decade); it presents a slight female predominance (2:1), and a higher percentage of positivity to Bcl-2. We present a 52-year-old man who showed a 2-year standing, non-ulcerated, round, 4 cm in diameter, red plaque, medially located on the dorsum. After biopsy the diagnosis of PCLBCL-LT was made on histopathological and immunohistochemical studies, the latter showing positivity to CD20, Bcl-2, and Bcl-6. After treatment with radiotherapy the patient has shown a 4.4-year follow-up free of disease.