Abstract
Summary
1. Ten samples of human milk collected from young, healthy, nursing women, whose sisters, mothers, or grandmothers had breast cancer, were examined with the aid of an electron microscope. Spherical particles, of a smooth surface and a high density† to the electron beam, varying in diameter from 20 to 200 mμ, in some instances grouped in pairs, or clusters, were found in all samples; they were particularly numerous, however, in 5 of the 10 samples examined. These spherical particles appeared to be similar to those previously observed in mouse milk known to contain the mouse mammary carcinoma agent.
2. Thirty-two control human milk samples, collected from young, healthy, nursing women having a family record apparently free from any malignant tumors for 2 preceding generations, were also examined with the aid of an electron microscope. Eleven of them were found to contain spherical particles essentially similar to those described above. Of the remaining 21 control milk samples, 17 were found to contain only occasional, isolated, single particles in some of the electron micro-scopic fields; the other 4 samples appeared to be free from spherical particles, but contained some unidentified debris.
3. No definite conclusions can be reached at this time as to the nature of the spherical particles revealed with the aid of the electron microscope in human milk.
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