Abstract

Inflammatory myofibroblastic tumors (IMT) of the uterus are often associated with pregnancy and are delivered with the placenta. We describe the clinical, pathologic, and molecular findings in nine cases of placental associated IMT (PaIMT). All the lesions were incidentally discovered at delivery or on placental pathological examination. Maternal age ranged from 21 to 41 (mean 30.6) years. Eight patients had high-risk pregnancies and, when known, all patients were multigravida. Macroscopically, eight tumors were well-defined ranging in size from 2 to 6 cm present at the maternal surface of the placenta (n=3), membranes (n=4), or separately delivered with the placenta (n=2). All nine lesions revealed classical IMT morphology with spindle cells associated with a lymphoplasmacytic infiltrate and thin elongated vessels. Five showed decidualization and five showed coagulative necrosis. All tumors expressed CD10. Of the seven tumors that were ALK positive, six were confirmed to have an ALK rearrangement by fluorescent in situ hybridization (FISH), whereas one failed FISH testing. Fusions included TIMP3-ALK (n=3), THBS1-ALK (n=2), and a novel SYN3-ALK fusion (n=1). Clinical follow-up was available in three patients, with no recurrence reported. There appears to be an increased frequency of uterine IMTs in pregnancy and associated with the placenta. No PaIMT has behaved aggressively, although follow-up has been quite limited. This may speak to a specific behavior of these tumors when associated with pregnancy.

View details for DOI 10.1016/j.humpath.2020.09.005

View details for PubMedID 32971128