Inflammatory Myofibroblastic Tumor Associated With the Placenta: Short Tandem Repeat Genotyping Confirms Uterine Site of Origin.

Inflammatory myofibroblastic tumor (IMT) is a neoplasm of intermediate malignant potential that only rarely involves the gynecologic tract. Several cases of IMT arising in various locations including the lung, bladder, trachea, and breast in association with pregnancy have been reported in the literature, and 3 cases involving the placenta have been previously described. We report 2 cases of IMT identified in association with pregnancy; the first was an intrauterine mass delivered entirely separate from the placenta and fetus, and the second was an incidental mass identified within the placental parenchyma following delivery. Short tandem repeat genotyping was used to compare tissue from the tumor and the placenta for both cases. Both tumors were determined to be of maternal origin, confirming that uterine IMTs may present within the placenta or as a separate mass following delivery. This demonstrates the utility of short tandem repeat genotyping in determining the origin of tumors presenting in association with the placenta.