Unexpectedly High Coexistence Rate of In Situ/Invasive Carcinoma In Phyllodes Tumors. 10-Year Retrospective and Review Study.

Objective: Phyllodes tumors (PTs) are a rare group of breast tumors. Most malignant transformations are in situ carcinomas that are extremely rare and are limited to individual cases in the literature. The presence of in situ/invasive carcinomas is important as this may alter clinical judgment and management. In this study, we aimed to determine the association of in situ/invasive carcinomas among PTs.

Materials and methods: This retrospectively designed study included cases diagnosed with PTs between 2011 and 2020 in the pathology department of a tertiary level hospital. Tumors were grouped into benign, borderline and malignant, according to stromal overgrowth, stromal atypia, stromal cellularity and mitotic activity. In addition, age, location, type of operation, tumor diameter, and surgical margin information were recorded. in situ and/or invasive carcinoma foci accompanying the PTs were assessed.

Results: A total of 29 patients diagnosed with PTs were identified, among whom 14 (48.2%) had benign PTs, 10 (34.4%) had borderline PTs, and 5 (17.2%) had malignant PTs. Of the patients with PTs, 3 (10.3%) had coexistent invasive carcinoma and 1 (3.4%) had carcinoma in situ. In this cohort the incidence of coexistence of PT and carcinoma was 4/29 (13.7%), which is much higher than previously reported (1.1% and 6%). The incidence of carcinoma was 2/5 (40%) in malignant PT patients and 2/10 (20%) in borderline PT patients. The coexistence of malignant PTs and carcinoma was significantly higher than those of benign and borderline PTs (p<0.05).

Conclusion: The multidisciplinary team dealing with breast diseases has a great responsibility in both diagnosis and treatment. We anticipate that these rates will increase with an increase in the awareness and importance of this coexistence of carcinoma and PTs.