Incidental choriocarcinoma confined to a near-term placenta.

A large solitary choriocarcinoma was found incidentally in a placenta from a 36-week gestation following caesarean section performed because of intrauterine fetal distress. Macroscopically, there appeared to be a large old infarct in the centre of the placenta proper. Microscopically, there was extensive central necrosis with a rim of viable trophoblastic tumour that had the typical morphology of choriocarcinoma. Although the tumour was floating within maternal blood and was also detected in direct contact with fetal vessels, no metastatic disease was reported in the subsequent 1 1/2 years either in the mother or in the child. Placental infarcts are often not examined histologically, and an intraplacental tumour may thus be missed. Central friability and an unusual colour should alert the pathologist and lead to histological clarification. The management of an incidentally discovered intraplacental choriocarcinoma should be an expectant one, consisting of extensive workup for any evidence of metastases and serial beta-HCG measurements in both mother and child.