Clinicopathologic spectrum of cutaneous manifestations in systemic follicular lymphoma. A study of 11 patients.

Follicular lymphoma is rarely diagnosed on the basis of only a cutaneous biopsy. Eleven patients with primary follicular lymphoma of lymph nodes who developed skin lesions were studied. Skin lesions involved the scalp, head and neck, trunk, and buttocks and were small cleaved cell type in four cases, large cell type in three cases, and mixed type in four cases. The follicular pattern with a bottom-heavy distribution was identified in only six of the 11 cases. One case showed a nodular, perivascular pattern in the deep dermis and subcutaneous tissue. Four cases were characterized by a diffuse pattern of lymphocytic infiltrate. One patient with a diffuse pattern had an isolated subepidermal band of lymphoma cells representing primary cutaneous T-cell lymphoma. Cutaneous involvement by lymphoma previously diagnosed as low-grade (follicular growth pattern) transformed to higher grade disease in five of ten asynchronous cases. The 5-year survival rate was 60% among the transformed cases and 100% among the nontransformed cases. Extranodal cutaneous involvement in follicular lymphoma occurred in 3.8% of cases. The correct histologic diagnosis in a skin biopsy specimen can be established in cases with a follicular pattern (60%) with conventional histologic criteria such as redundancy of follicles, uniformity of follicular center cell composition, lack of interspersed phagocytic histiocytes, and absence of immunosecretory cellular elements such as plasma cells and immunoblasts.