Prognostic significance of atypical mitotic figures in smooth muscle tumors of uncertain malignant potential (STUMP) of the uterus and uterine adnexa

We aimed to assess whether the presence of atypical mitotic figures (AMF) in smooth muscle tumors of uncertain malignant potential (STUMP) of the uterus and uterine adnexa is associated with increased risk of recurrence, and the association of AMF with the Stanford criteria, that is, significant cytologic atypia, mitotic index ≥ 10/10HPF, and coagulative tumor cell necrosis (CTCN). A systematic review was performed to identify all studies reporting the presence of AMF and oncologic outcomes in STUMP series. Fisher’s exact test was used to assess the association of AMF with the three Stanford parameters. Kaplan–Meier and Cox regression survival analyses with hazard ratio (HR) calculation were performed to assess the association between AMF and STUMP recurrence. A p-value < 0.05 was considered significant. Five studies with 80 STUMPs were included, out of which 23.8% had AMF. AMF were significantly associated with the presence of significant atypia (p = 0.023), but not with the presence of a mitotic index ≥ 10/10HPF (p = 0.769), CTCN (p = 1), or more than one Stanford parameter (p = 0.171). AMF was not significantly associated with the risk of STUMP recurrence at both univariate (HR = 0.366; p = 0.188) and multivariate analyses (HR = 0.528; p = 0.463). In STUMP of the uterus and uterine adnexa, AMF are more common in the case of significant cytologic atypia, but do not seem to increase the risk of recurrence. Further studies are necessary in this regard.