Mucinous carcinoma is more common in post-menopausal women. Pure mucinous carcinomas comprise up to 2% of all breast cancers. Focal mucinous differentiation is seen in additional 2% of breast cancers. For prognostic reasons, the term mucinous carcinoma should be applied to pure tumors showing stromal mucin in >90 of the tumor. Grossly, the tumor is generally well-circumscribed and has a gelatinous or jelly-like bluish-gray cut surface.