Localized, nodular pseudolymphomas are more common and typically mimic B cell lymphoma. It should be noted that there are a variety of specific diseases that are sometimes referred to as pseudolymphomas, simply because they may resemble lymphoma. These disorders often show broad patches and plaques and often mimic cutaneous T-cell lymphoma. Examples include actinic reticuloid, lymphomatoid contact dermatitis and lymphomatoid drug eruptions. In pseudolymphoma, lymphocytes and other inflammatory cells are recruited to the skin in response to known or unknown stimuli.
Most cases are idiopathic.
A discrete subset of pseudolymphoma, borrelial lymphocytoma, is seen primarily in Europe in areas endemic for the tick Ixodes ricinus. It is a response to infection by Borrelia burgdorferi afzelius conferred by tick bite. Another subset of pseudolymphoma is the result of an unusual systemic response to medications, typically anti-convulsants. This syndrome is addressed elsewhere within this textbook in a chapter entitled Drug-induced Pseudolymphoma Syndrome. Localized variants rarely result in morbidity other than minor pain or pruritus.