Introduction/Background Uterine leiomyosarcoma (LMS) is a rare uterine malignancy tumor originated from smooth uterine muscle. Compared with other types of uterine cancers, LMS is an aggressive tumor associated with a high risk of recurrence and death. Most cases are diagnosis incidentally after a surgery for presumed benign uterine leiomyoma. Sometimes patients may describe symptoms as vaginal bleeding or abdominal pressure due to a rapid uterine growth. The goal of this study is to determinate the clinical features in patients with LMS and the influence of type of diagnosis, comparing unexpected versus suspected LMS.

Methodology Retrospective observational study of patients diagnosed with LMS in the Gregorio Marañon Hospital (1985 – 2021). A comparation between groups of incidental and suspected diagnosis was performed.

Results Table 1 shows results. 52 patients have been diagnosed of LMS. In contrast with previous analysis, in our study less than 50% of the patients were incidentally diagnosed after a myomectomy or a hysterectomy for presumed benign pathology, meanwhile 55,8% were suspected after abnormal vaginal bleeding and/or rapid growth of a uterine leiomyoma. The age at diagnosis was significant lower in the group of incidental diagnosis and these patients were significant less associated with comorbidities. Most of the patients were diagnosed at early stages and almost all of them received surgical treatment but this percentage is higher when the diagnosis is unsuspected. This could explain the reason why those patients are associated with higher rates of complete resection, and lower needed of adjuvant treatment and recurrence. Although global risk of recurrence and death is high, as is has been descripted previously, our study shows a significant higher disease-free survival rate when diagnosis are unsuspected.

Conclusion LMS are aggressive uterine tumors leading to elevated rates of recurrence and death. The events leading to the diagnosis may influence the prognosis.