This observational study aims to gather comprehensive data on primary ovarian leiomyosarcoma (POLMS). This extremely rare malignancy accounts for less than 3% of primary ovarian malignancies and has an incidence of only 1% among ovarian cancers. This national, retrospective and prospective multicenter study will collect and analyze historical cases of POLMS with remote diagnoses accessed through clinical case reviews and newly identified cases. The study aims to expand a previously identified series of 113 cases described in the literature, uncovering patterns in diagnosis, treatment, and outcomes and ultimately establishing evidence-based guidelines for the optimal management of this rare and aggressive cancer.

This study adopts a national, multicenter, observational design, incorporating both retrospective and prospective methodologies to collect and analyze primary ovarian leiomyosarcoma (POLMS) cases. The retrospective component will include cases diagnosed since 1980, leveraging institutional archives and clinical case reviews.

Data collection will be standardized using an electronic Case Report Form (eCRF) implemented on REDCap. All data will be centralized for uniformity and undergo rigorous validation to ensure consistency across centers. Findings will be reported in aggregated form to preserve patient confidentiality.

The study will gather extensive data points, including:

• Patient demographics.
• Clinical presentation and tumor characteristics (symptoms, tumor markers such as CA-125, CEA, and Ki-67).
• Treatment modalities (surgical details, lymphadenectomy, chemotherapy, radiotherapy, or hormonal therapy).
• Recurrence patterns and outcomes (disease-free survival, overall survival).
• Immunohistochemical findings (positivity for desmin, SMA, and vimentin). The statistical analysis primarily involves descriptive and exploratory techniques to identify patterns and correlations within the dataset.

Inclusion Criteria:

• Diagnosis of primary leiomyosarcoma of the ovary;
• Patients diagnosed with POLMS for whom data relating to diagnosis and treatment are available.
• Aged between 18 and 99 years

Exclusion Criteria:

- All patients with other forms of ovarian sarcoma (rhabdomyosarcomas, fibrosarcomas, stromal cell sarcomas) and patients diagnosed with leiomyosarcoma of the uterus will be excluded.

Only individuals assigned female at birth are eligible to participate in this study.

Consent for study participation will be obtained from living patients during follow-up visits. Historical cases with remote diagnoses since 1980 will be accessed through clinical case reviews in the databases of each participating center. For patients lost to follow-up or deceased, a waiver of informed consent has been obtained from the Ethics Committee by applicable regulations.