UMBILICAL-CORD PSEUDO-VASCULITIS FOLLOWING 2ND-TRIMESTER FETAL DEATH - A CLINICOPATHOLOGICAL AND IMMUNOHISTOCHEMICAL STUDY OF 13 CASES

Amniotic fluid bacterial infection is an occasional cause of second tr imester septic abortion. We describe an autolysis-related histological artifact, umbilical cord 'pseudo-vasculitis', which can erroneously i mplicate amniotic bacterial infection in fetal death, Clinicopathologi cal features of 13 second trimester fetal deaths with umbilical cord p seudo-vasculitis are reported, In four cases (31%), an incorrect patho logical diagnosis of umbilical vasculitis had initially been rendered, Umbilical cords from five cases of pseudo-vasculitis and one comparis on fetus (18-week septic abortion with true umbilical vasculitis), wer e studied with chloroacetate esterase and with immunohistochemical sta ining for myeloperoxidase, muscle-specific actin (HHF35) and smooth mu scle actin. Histologically, umbilical pseudo-vasculitis exhibited nume rous small, rounded, degenerating cells with irregular, multilobed nuc lei (closely resembling neutrophils) located within the umbilical vess el wall. Immunohistochemical studies demonstrated that all cells resem bling neutrophils were of smooth muscle origin, Moderate to severe fet al autolysis was present in all cases of umbilical pseudo-vasculitis, suggesting that this finding represents autolysis of umbilical vascula r smooth muscle secondary to post mortem fetal retention, Vascular smo oth muscle in other fetal and placental locations did not demonstrate the finding, suggesting that this striking degenerative artifact of sm ooth muscle is restricted to the umbilical cord.