Incidence and Predictors of Unexpected Malignancy in Benign Myomectomy or Hysterectomy

Introduction Detection of gynecological cancers preoperatively is imperative for practitioners for optimal patient management and outcome. This study aimed to estimate the incidence of unexpected malignancy (UM) in patients who underwent hysterectomy or myomectomy for presumed benign indications and to detect the predictive factors of UM. Methods A retrospective analytical study that included patients who underwent hysterectomy or myomectomy for benign indications from January 1st, 2016, to December 31st, 2020, was conducted at the Department of Obstetrics and Gynecology at Salmaniya Medical Complex, Bahrain. The main outcome was the overall incidence of UM and the incidence of each malignancy. Characteristics of UM were compared with benign pathologies. Fisher's exact and Pearson's chi-square tests were used to compare categorical variables and the Mann-Whitney U test or student's t-test for continuous variables. Binary logistic regression was used to identify the predictors of occurrence of UM. Confidence interval (CI) was set at 95%. A probability value (p-value) less than 0.05 was considered statistically significant. Results Out of 513 patients who underwent hysterectomy or myomectomy, 379 (73.9%) fulfilled the inclusion criteria, 314 (82.8%) hysterectomies and 65 (17.2%) myomectomies. The overall incidence of UM was 1.3% (n=5/379), 1.3% (n=4/314) among hysterectomies and 1.5% (n=1/65) among myomectomies. Three (0.8%) pre-malignant pathologies were identified: one (0.26%) smooth muscle tumor of unknown malignant potential, leiomyoma with bizarre nuclei, and mucinous borderline tumor of endocervical type of ovary each. The types of UM were sarcomas in three (0.26%) patients (two (0.5%) leiomyosarcoma and one (0.26%) endometrial stromal sarcoma) and endometrial adenocarcinoma and ovarian cancer in one (0.26%) patient each. No significant difference was found between the characteristics of UM and benign pathologies. Conclusion Although this study demonstrated a low incidence of UM among both hysterectomies and myomectomies, the age at the diagnosis of our patients with UM was as young as 34 years of age, and sarcomas were the most common type of UM. Disconcertingly, none of the studied independent variables had significantly predicted the occurrence of UM.