Introduction/Background Serous Tubal Intraepithelial Carcinoma (STIC) is considered the main precursor of high-grade serous carcinoma (HGSC). There are no standardized diagnostic criteria; an algorithm combining histological and immunohistochemical (IHC) analysis has been proposed by Kurman to improve the standardization. In women undergoing Risk Reducing Salpingo Oophorechtomy (RRSO), the diagnosis of STIC is essential for the assessment of the risk of recurrence in this group of women.

Methodology A retrospective study was conducted in two Gynaecological Oncology Units (Mauriziano Hospital Torino and IRCC Candiolo, Italy). Pathological reports of the fallopian tubes of 128 BRCA mutation carriers/high risk women (who underwent RRSO or surgery for ovarian cancer) and 222 women at low risk for the development of breast and ovarian cancer (who underwent surgery for ovarian cancer or benign diseases) were analyzed searching hyperplasia, atypia, dysplasia, STIC and tubal carcinoma and classifying these lesions as not suspicious/suspicious/unequivocally STIC. Subsequently, in high risk patients with histological alterations, IHC stains (p53 and Ki67 index) were performed, to apply Kurman's algorithm.

Results Prevalence of pathological tubal lesions was higher in BRCA/ high risk patients compared to low-risk (14,8% vs. 4% p=0.0004; OR 4,2 (IC 1,8–9,4)). After IHC analysis 78.6% of ‘not suspicious for STIC’ alterations, were defined as normal/reactive epithelium. The remaining lesions (21.4%) were classified as Serous Tubal Intraepithelial Lesions (STIL). The Cohen concordance index K between histological diagnosis alone and its association with IHC was 0,019.

Conclusion The routinely association of IHC and histological analysis may help pathologists in producing more congruous and reproducible diagnoses, improving the assessment of atypical intermediate tubal lesions. Since the prognosis and the correct management of women undergoing RRSO diagnosed with STIC is still debated, this new type of combined technique of analysis may influence clinical attitudes when STIL or STIC are found.

Disclosure Nothing to disclose