Fetal Vascular Obstructive Lesions: Nosology and Reproducibility of Placental Reaction Patterns

Abstract

The purpose of this study was to assemble and test the reliability of a complete set of the placental reaction patterns seen with chronic fetal vascular obstruction in the hope that this might provide a standardized diagnostic framework useful for practicing pathologists. Study cases (14 with fetal vascular obstructive lesions, 6 controls) were reviewed blindly by seven pathologists after agreement on a standard set of diagnostic criteria. Majority vote served as the gold standard and 80% of the 180 diagnoses rendered (9 diagnoses each for 20 cases) were agreed upon by at least six of the seven scores. The sensitivity of individual diagnosis relative to the group consensus averaged 83% (range, 69-100%) and specificity averaged 91% (range, 86-100%). Reproducibility was measured by unweighted kappa-values and interpreted as follows: < 0.2, poor; 0.2-0.6, fair/moderate; > 0.6, substantial. Kappa values for lesions of distal villi were generally superior to those for lesions involving large fetal vessels: avascular villi (0.49), villous stromal-vascular karyorrhexis (0.58), and villitis of unknown etiology (VUE) with stem villitis and avascular villi (0.65) versus large vessel thrombi (any vessel, 0.34; chorionic plate vessel, 0.40) and intimal fibrin cushions (recent, 0.47; remote, 0.78). Reproducibility for a global impression of any villous change consistent with chronic fetal vascular obstruction was substantial (0.63), while that for a more severe subgroup was moderate (0.44). Three points are worthy of emphasis. Our system separately recognizes, but later combines, uniformly avascular villi and villous stromal-vascular karyorrhexis as manifestations of the same underlying process. We propose that this combined group of villous lesions be dichotomized with the terms fetal thrombotic vasculopathy or extensive avascular villi (and/or villous stromal-vascular karyorrhexis) being reserved for the group with 15 or more affected terminal villi per section. Scattered foci of avascular villi (and/or villous stromal-vascular karyorrhexis) could be used to describe less severe cases. Finally, we distinguish VUE with stem villitis and avascular villi (obliterative fetal vasculopathy) as a distinct process with substantial perinatal morbidity.

Placental Vascular Pathology Findings and Pathways to Preterm Delivery

“…In addition, previous studies have showed that interrater reliability for diagnosing histologic evidence of vasculature-related pathology is not high (22,24,31), perhaps because there is a lack of agreement as to what constitutes a critical mass of findings for the designation ''positive.'' Major strengths of this study include the sample, which was recruited from multiple community clinics and was shown to be highly comparable to community women giving birth during this period.…”

Increased Prevalence of Fetal Thrombi in Monochorionic-Twin Placentas

“…Avascular villi were defined by Ն15 affected terminal villi per section. 13 Chorangiosis was defined by 10 villi with Ն10 vascular channels. 14 Tenney-Parker change (excessive syncytial knotting) was defined by Ն30% of the tertiary villi with syncytial buds.…”

Placental Pathology in Intra Uterine Growth Retardation

“…10 In the present study incidence of chronic villitis was 14% in AGA group and 32% in IUGR group. In the present study, the placentas were significantly smaller in IUGR group than AGA group.…”