Detection of atherosis in preeclamptic placentas: comparison of two gross sampling protocols.

Two standardized gross sampling protocols were compared with the intention of maximizing the histologic detection rate of atherosis in at-risk (i.e., preeclamptic) placentas. The first, 4-block, protocol was designed to be broadly representative of good current practice (central, edge, en face shave, and membrane roll blocks). A second, 5-block, protocol incorporated all of protocol 1 with the addition of a block composed of multiple flat membrane leaves stacked and sectioned 5 times at 200-mum intervals. Data were available on the first protocol from 80 consecutive accessioned cases of singleton preeclamptic placentas and on the second protocol from 40 cases. Criteria for diagnosis for atherosis were relatively rigorous and excluded "burnt-out" fibrinoid lesions in which foam cells were not positively identified. With the first protocol, atherosis was detected in 30 of 80 (37.5%) of placentas studied. With the second protocol, atherosis was detected in 25 of 40 (62.5%) of placentas studied. This increase was related to a high detection rate of 50% in the flat membrane stack block. Evaluation of the more traditional forms of block produced atherosis detection rates of 2.5% for central full-thickness blocks, 14% for edge blocks, 10% for en face shave blocks, and 25% for membrane rolls. The flat membrane stack was found to be the single most sensitive block for detection of atherosis. When used in conjunction with traditional blocking techniques, it offers significantly increased reliability for detection of atherosis in placentas when maternal vascular compromise is suspected.