Clinical and pathological investigation of microscopic mole.

To clarify the pathological significance of the quasi-mole lesions of the placenta, morphological and morphometrical study of villi was undertaken. The material comprised products of conception in 70 cases of artificial abortion, 110 cases of spontaneous abortion and 11 cases of complete mole: The artificially aborted material was regarded as having normal villi. The products, after being observed with a stereo microscope, were subjected to microscopic examination of paraffin sections. A vascular villi with central liquefaction and proliferation of trophoblasts were found not only in the group of overt mole but also in spontaneously aborted and even in artificially aborted material, though less frequently. By morphometry, villi were shown to be involved in these changes even when macroscopically there seemed to be no significant abnormalities, a condition we prefer to call "microscopic mole." This was prevailing particularly in cases in which the average minor axis of villi exceeded 1 mm; it became more predominant with enlarging axis, gradually approaching the shape of complete mole. Some of the cases with enlarged villi proved to develop later invasive mole. Thus, whether or not the average minor axis exceeds 1 mm is likely to have a profound clinical significance.