Ultrastructural criteria in evaluating leukemic infiltration in prepubertal testicular biopsies.

The diagnosis of leukemic infiltration in the testis by routine histology is not always possible. During the past 5 years, 46 bilateral testicular biopsies from prepubertal boys were examined by electron microscopy for the purpose of establishing the presence or absence of leukemic infiltration. The ultrastructure of the cells of acute lymphoblastic leukemia is described from the positive cases and compared with cases from the literature. Variations in ultrastructure between the T-cell, B-cell, and "null cell" types are discussed. The ultrastructure of the normal prepubertal cellular elements, which include immature Leydig cells, primitive fibroblastic cells (intertubular), and attenuated peritubular fibroblasts, is described. Ultrastructural criteria are summarized that enable a definitive evaluation of cases that are equivocal by histologic examination.