Malignant "histiocytic" lymphoma in childhood

Forty-one cases of childhood "histiocytic" lymphoma were studied morphologically and immunologically to determine whether this tumor type is composed of true histiocytic cells. Lysozyme and alpha-1-antichymotrypsin were used as markers for histiocytes, and cytoplasmic immunoglobulins were used as markers for B cells. Both indirect immunofluorescence and immunoperoxidase methods were used for functional characterization of tumor cells. Eight different subgroups were identified in the series, and only one case was proved to be true histiocytic lymphoma. When survival was evaluated for different subgroups, excluding convoluted lymphocytic, unclassified, and true histiocytic lymphomas, mixed follicular cell lymphoma had the most favorable prognosis; six of seven patients survived for at least one year. Immunoblastic lymphoma, by contrast, had an unfavorable prognosis; none of four patients were alive one year after diagnosis. The difference is statistically significant (P < 0.05) by chi-square analysis. Other groups of lymphoma (large cleaved, large noncleaved, and small noncleaved) had an intermediae prognosis (three of five, six of nine, and five of nine patients surviving at one year). Our results indicate that "histiocytic" lymphoma is a morphologically heterogeneous group of neoplasms, mostly not related to true histiocytes, and that morphologic subclassification may be useful in predicting prognosis.