The aim of the current study was to estimate the incidence of unexpected leiomyosarcoma (LMS) in patients who underwent surgery due to leiomyomas in Konya province, and to contribute to the literature discussing comparisons with similar studies. The digital archives of eight high-volume hospitals were studied for surgeries performed due to leiomyomas between January 2012 and January 2019, and leiomyosarcoma incidence was calculated based on the data obtained. Twenty-one patients in 3703 cases were found to have unexpected leiomyosarcoma, which means we can expect one leiomyosarcoma in 176 (0.56%) surgeries. Six more malignant tumours were detected among the remaining cases. Thus, our study estimated the incidence of unexpected leiomyosarcoma as 1/176 (0.56%), which is higher than most of the studies in the literature justifying the debate started by the FDA in 2014. As the tumour biology is not yet clear, and the incidence of unexpected leiomyosarcoma tends to be so high, the key focus must be to try to detect uterine leiomyosarcomas preoperatively for robust patient care.IMPACT STATEMENTWhat is already known on this subject? The incidence of unexpected leiomyosarcoma varies widely from 1/498 to 1/8300 depending on the study method and the type of procedure, and there is still controversy, even after the FDA statement that led to a major restriction in laparoscopic surgeries due to concerns about inadvertent morcellation of leiomyosarcomas. What do the results of this study add? To the best of our knowledge, the current study found the highest incidence of unexpected leiomyosarcoma, and consequently a serious evaluation of all patients undergoing surgery due to leiomyomas preoperatively considering a leiomyosarcoma candidate is recommended. What are the implications of these findings for clinical practice and/or further research? Studies on tumour biology and novel markers must be supported for accurate preoperative diagnosis of leiomyosarcoma.