Primary squamous cell carcinoma of the breast (PSCCB) is a rare clinical classification of breast tumors. Little is known about its clinicopathological features, prognosis and potential therapeutic strategies. The purpose of this study is to evaluate the effect of postoperative radiotherapy (PORT) on patients with squamous cell carcinoma (SCC) of the breast.
We retrospectively analyzed patients diagnosed with PSCCB in our center. All pathological slides were reviewed by an experienced pathologist to confirm the diagnosis. Furthermore, we searched the public database for patients with SCC of the breast. Then, we analyzed the clinicopathological features, treatment methods and patient outcomes.
We identified 14 patients with primary SCC of the breast in our center. Additionally, 739 patients with SCC of the breast from the Surveillance, Epidemiology and End Results (SEER) database were diagnosed between 1975 and 2016. Only 453 patients who underwent surgery were included in this study. Patients from the SEER database had a more advanced tumor node metastasis (TNM) stage than patients from our center. The median overall survival (OS) of all patients was 104 months (95% confidence interval [CI], 87.2-120.8 months), and the 5-year OS was 60.8% (95% CI, 56.1%-65.5%). Most of the patients (58%) tested negative for hormonal receptor expression. Multivariate analysis showed that PORT was an independent prognostic factor for OS.
The results of our study demonstrate that SCC of the breast presents aggressive behavior with unique clinical characteristics. PORT improved OS significantly in patients with SCC of the breast. Longer-term studies are needed to confirm our findings.

© 2020 John Wiley & Sons Australia, Ltd.