Primary Cutaneous B-Cell Lymphomas.

B-cell lymphomas occurring in the skin often tend to be of systemic origin with secondary cutaneous involvement. Primary cutaneous B-cell lymphomas tend to be indolent disorders, with the exception of primary cutaneous diffuse large B-cell lymphoma-leg type (PCDLBCL-LT). In indolent conditions, the distinction between cutaneous lymphoma and cutaneous lymphoid hyperplasia can be difficult. Integration of all available information, including the clinical setting, is crucial to arriving at the appropriate diagnosis. In this review, we cover the diagnostic approaches to primary cutaneous marginal zone lymphoma, primary cutaneous follicle center lymphoma, and PCDLBCL-LT, and discuss their differential diagnosis.