Secondary Lymphomas of the Skin

Malignant lymphomas that secondarily involve the skin are relatively common and may be difficult to distinguish from primary skin lymphomas. While the morphologic features of primary and secondary lymphomas of the skin are often very similar, the clinical behavior of primary and secondary disease is often dramatically different. Although large series of secondary cutaneous lymphomas are uncommon, secondary lymphomas or lymphomas that involve both nodal sites and the skin at presentation appear to represent approximately 25% of all cutaneous lymphomas and up to 50% of cutaneous lymphomas other than mycosis fungoides. In a recent survey of cutaneous lymphomas diagnosed at Stanford University, 24.6% were considered secondary based on a prior or simultaneous diagnosis of non-cutaneous lymphoma. The frequency of each lymphoma type among secondary cutaneous lymphomas at Stanford is given in parentheses after each disease type below. In contrast to primary cutaneous lymphoma, secondary cutaneous lymphomas show a B cell predominance. Similar to other sites of lymphoma, diffuse large B cell lymphoma and follicular lymphoma secondarily involving the skin are relatively common. However, secondary cutaneous involvement by T and NK cell proliferations is still more common in the skin than the frequency of primary nodal NK and T cell lymphomas.