Localization of Indium-111 leukocytes in noninfected neoplasms

Indium-111-labeled autologous leukocyte studies in general carry a high sensitivity, specificity, and accuracy for the investigation of infections and abscesses. However, past studies have described sporadic cases in which ¹¹¹In leukocytes localized in tumors. Our experience using ¹¹¹In leukocytes for the investigation of fever of unknown origin in cancer patients, however, indicates a relatively high incidence of ¹¹¹In leukocyte localization in noninfected neoplasms. Out of the 61 patients studied for fever of unknown origin, 21 patients (34%) manifested abnormal localization of ¹¹¹In leukocytes in neoplasms without clinical evidence of infection. These included patients with abnormal localization in: (a) lymph nodes, (b) soft-tissue tumors, and (c) bone neoplasms. The tumors included both primary and secondary lesions, and hematologic as well as solid tumors. The mechanism of ¹¹¹In leukocyte localization in tumors is still not completely explained. Interpretations of ¹¹¹In leukocyte studies in cancer patients with fever should take into consideration the possibility that localization may occur in neoplastic tissue per se and does not always indicate the presence of infection.