Inflammatory myofibroblastic tumors associated with the placenta: a series of 9 cases

Hum Pathol. 2020 Dec;106:62-73. doi: 10.1016/j.humpath.2020.09.005. Epub 2020 Sep 21.


Inflammatory myofibroblastic tumors (IMTs) 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 placenta-associated IMT (PaIMT). All the lesions were incidentally discovered at delivery or on placental pathological examination. The 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) and 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 anaplastic lymphoma kinase (ALK) positive, six were confirmed to have an ALK rearrangement by fluorescence 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.

Keywords: ALK1; Inflammatory myofibroblastic tumor; Placenta; Placental masses; SYN3.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Adult
  • Biomarkers, Tumor / analysis
  • Biomarkers, Tumor / genetics
  • Databases, Factual
  • Female
  • Gene Fusion
  • Humans
  • Hysterectomy
  • Incidental Findings
  • Myofibroblasts / chemistry
  • Myofibroblasts / pathology*
  • Placenta / chemistry
  • Placenta / pathology*
  • Pregnancy
  • Pregnancy Complications, Neoplastic / genetics
  • Pregnancy Complications, Neoplastic / metabolism
  • Pregnancy Complications, Neoplastic / pathology*
  • Pregnancy Complications, Neoplastic / surgery
  • Treatment Outcome
  • Tumor Burden
  • Uterine Neoplasms / chemistry
  • Uterine Neoplasms / genetics
  • Uterine Neoplasms / pathology*
  • Uterine Neoplasms / surgery
  • Young Adult


  • Biomarkers, Tumor