Histopathologic subclassification of diffuse histiocytic lymphoma and response to therapy.

In 55 patients with diffuse histiocytic lymphoma (Stages I-IV), the disease was subclassified as large cleaved-cell (17 patients), large noncleaved-cell (12 patients), mixed follicular-center cell (14 patients), blastic (6 patients), and pleomorphic pyroninophilic (6 patients). Two-year survival rates for these subclasses were 47%, 42%, 64%, 17%, and 33%, respectively, suggesting that histopathologic subclass is an important prognostic factor in diffuse histiocytic lymphoma. The mean tumor dose that produced local control in 22 patients who were treated with radiation therapy alone was 4,834 rad (48.34 Gy), whereas the mean tumor dose for local control when chemotherapy was used in combination with radiation therapy (16 patients) was 3,679 rad (36.79 Gy). This suggests that when chemotherapy is used with radiation therapy, a lower tumor dose will be sufficient to achieve local control than when radiation therapy is used alone. In addition, 43% of the patients who presented with an intra-abdominal primary lymphoma experienced local failure following treatment. It is recommended that patients who present with an abdominal primary tumor be treated aggressively with combined modality therapy whenever feasible.