Clear Cell Carcinoma of the Breast: A Rare Breast Cancer Subtype – Case Report and Literature Review

BACKGROUND: Glycogen-rich clear cell breast carcinoma is a rare histological breast cancer subtype. Its prognosis may vary depending on specific clinical and pathological characteristics such as low grade, strong positivity of estrogen receptor (ER) expression and early diagnosis. CASE PRESENTATION: We present the case of a 53-year-old woman with a bleeding 10-cm-diameter mass in the left breast. The histological examination showed a poorly differentiated tumor with malignant cells characterized by abundant clear cytoplasm. The diagnosis of clear cell carcinoma was based on the histological characteristics of the tumor, and a nonmammary origin was initially ruled out. The tumor was triple negative [i.e. ER, progesterone receptor (PR) and HER2 negative]. Four months after the initial locoregional treatment, the patient developed lung and distant lymph node metastases. CONCLUSIONS: Glycogen-rich clear cell carcinoma of the breast is a rare tumor. Early diagnosis, absence of lymph node metastases and ER/PR positivity are associated with a better prognosis, as in other common breast cancer subtypes.