Thymic localization of gallium-67 in pediatric patients with lymphoid and nonlymphoid tumors.

To determine the significance of 67Ga localization in the thymus of children, 142 67Ga photoscans from 45 children with various tumors were studied. Sixty-nine photoscans were taken for 17 cases of lymphoma, 73 photoscans were made for 28 cases of nonlymphoid tumors. Thymic localization of 67Ga was positive in 16 (36%) of the 45 patients and in 30 (21%) of the 142 photoscans. Positive thymus scans were seen in five (29%) of the 17 cases of lymphoma and 11 (39%) of the 28 solid tumors. The positive incidence was highest (90%) in ages 1-2 yr old. Of the eight grade 2 (strong positive) patients, the thymus in one case of Hodgkin's disease was diagnosed as malignant and the other seven solid tumor cases were nonmalignant. Most of the latter seven cases became positive after beginning of treatment (surgery and/or chemotherapy). Although the precise mechanism is not well understood, thymic localization of 67Ga may represent immunologic response to tumors, especially in infants with nonlymphoid neoplasms.