In routine diagnostic practice, how many sections should we examine from cases of products of conception?

In order to determine whether a single representative section taken from routine specimens of products of conception would contain sufficient material to trigger a more comprehensive search for the features of a hydatidiform mole, cases of gestational trophoblastic disease submitted over a five year period were reviewed. Partial hydatidiform moles were either suspected or diagnosed on the first histological section in 46 (92%) cases. In the remaining four cases, although abundant placental tissue showing diagnostic features was available in later blocks, most of the tissue in the first block consisted of endometrial tissue with only occasional chorionic villi being identified. The current study shows that a molar gestation can be suspected after examining a single tissue block, providing that it contains a representative number of chorionic villi. If a molar pregnancy is suspected clinically or pathologically, additional blocks should be examined to secure the diagnosis and classify the condition.