BackgroundAmong the many challenges in cancer diagnosis is the early distinction between metastatic cancer and a secondary tumor. This difficulty stems from the lack of markers that offer high sensitivity and specificity and can be easily applied in routine laboratory work. An example of this challenge is distinguishing gastric metastases originating from breast cancer from a gastric primary tumor. Hepatocyte nuclear factor 4 alpha (HNF4A) has been suggested as a potential marker in these cases.The aim of this study was to analyze the expression of HNF4A, estrogen receptor (ER), progesterone receptor (PR) and gross cystic disease fluid protein 15 (GCDFP-15) in a Brazilian cohort.MethodsWe performed immunohistochemistry analysis of HNF4A, ER, PR and GCDFP-15 in 126 patients divided into three cohorts: primary breast cancer, primary gastric cancer and both types of tumors.ResultsOur data confirmed the sensitivity and specificity of the HNF4A marker compared to other currently used clinical markers.ConclusionHNF4A alone could be a gold standard marker for distinguishing primary gastric cancer from breast metastasis, thus validating its potential clinical use, especially in populations with high genetic diversity.Electronic supplementary materialThe online version of this article (doi:10.1186/s13000-017-0635-2) contains supplementary material, which is available to authorized users.

Introduction: Breast sarcoma is a rare form of malignancy that arises from connective tissue, comprising less than 5% of all sarcomas. Undifferentiated pleomorphic sarcoma (UPS) of the breast is a rare and aggressive subtype of radiation-induced sarcoma that can occur in treated breast cancer patients. The diagnosis is challenging and often missed due to the low incidence, long latency period, unspecific imaging finding, and difficulties in clinical and histological detection. Case report: A 56-year-old woman was diagnosed with early-stage triple-negative breast cancer in 2013 and underwent breast-conserving therapy (BCT). After five years follow-up, she developed mastalgia and breast induration, and after mammography and ultrasound without suspicious lesions, a magnetic resonance imaging (MRI) was performed and showed a highly suggestive malignancy mass measuring 8.0 cm and invading the chest wall. The core biopsy revealed a spindle cells malignant tumor, negative for pan cytokeratin and most of immuno-histochemical markers, suggesting sarcoma, but requiring investigation of surgical specimen to exclude metaplastic carcinoma. She underwent Halsted radical mastectomy, full-thickness left anterior chest wall resection contemplating segments of the 4th and 5th ribs and reconstruction with synthetic mesh. The surgical specimen evidenced a UPS with clear margins. The patient had good postoperative recovery and remains in follow-up with the mastology team. Conclusion: This report shows that radiation-induced sarcomas of the breast can be difficult to diagnose, and how later treatment can demand a major surgery with higher morbidity. Prognosis may improve if detected early.