Cutaneous lymphomas: correlation of histochemical and immunohistochemical characteristics and clinicopathologic features.

Twenty-four cases of cutaneous lymphomas were classified as T-cell (18 cases), B-cell (three cases), and true histiocytic (three cases), on the basis of the histochemical and immunohistochemical characteristics. Important differences in clinical and histopathologic features exist among these three types: skin lesions of T-cell lymphoma are usually chronic, pruritic, and sometimes ulcerative; those of B-cell lymphoma are nonpruritic and nonulcerative; lesions of true histiocytic lymphoma are often pruritic and ulcerative. All three patients with true histiocytic lymphoma died within six months of diagnosis. Two of the three patients with B-cell lymphoma died within two years of diagnosis. Only two of the 18 patients with T-cell lymphoma died, one after 12 years and the other after six years. Histologically, B-cell lymphoma shows a grenz zone in the upper dermis and absence of epidermal involvement; both T-cell and true histiocytic lymphomas show epidermal infiltration and absence of a grenz zone. True histiocytic lymphoma can appear similar to T-cell lymphoma clinically and histologically by routine examination, but histiocytic lymphoma has a much worse prognosis. Histochemical and immunohistochemical studies are very helpful in the differential diagnosis.