Metastatic frequency of spontaneous mammary carcinoma in mice following biopsy and following local roentgen irradiation.

The risk of spread of malignant tumors follow ing biopsy has been the subject of numerous in vestigations (2), while only a few workers have been concerned with this risk following local roent gen irradiation. Yamamoto (4) found an increased frequency of metastasis to bone following local roentgen irradiation of the Kato rabbit sarcoma with doses of 600-1,800 r. Kaplan and Murphy (3) investigated the frequency of remote métas tases following local roentgen irradiation of the Bagg-Jacksen mammary carcinoma 755 trans planted into C57BL mice. Pulmonary métastases occurred in 44 per cent of 62 mice irradiated locally, as against 9.6 per cent of 52 controls.