Glycogen-rich clear cell carcinoma of the breast with solid papillary pattern: Two cases with heterogeneous clinicopathological features

Invasive breast cancer is a heterogeneous disease, both in its histopathological classification and clinical course. Glycogen-rich clear cell carcinoma of the breast is an extremely rare subtype of invasive breast carcinoma, accounting for up to 3% of all breast carcinomas. The tumor is composed of polygonal cells with abundant clear cytoplasm containing glycogen and has a very controversial prognosis. Solid papillary pattern is an uncommon morphological variant of breast carcinoma which is associated with indolent behavior in the absence of an invasive component. To date, there are only three cases of glycogen-rich clear cell carcinoma with solid papillary pattern reported in the English literature. In this article, we present two cases of glycogen-rich clear cell carcinoma of the breast, encountered in our daily clinical practice over a period of 5 years (2015-2020) and perform a brief review of currently published literature. Unlike most cases of glycogen-rich clear cell carcinoma documented to date, follow-up of our case featuring solid papillary pattern revealed extremely favorable clinical outcome, suggesting a better prognosis for tumors with this morphology.