"this type is more likely to be infiltrative and carries a much worse prognosis."
"the growth pattern is often expanding, cellularity and mitotic activity are low, and cell atypia is not very prominent"
"The majority of well-marginated breast masses are benign but 10-20% of breast malignancies also could be well-circumscribed such as mucinous tumours; others include papillary, medullary, and metaplastic carcinomas as well as malignant phyllodes tumours. Because of the different patterns of mammogram and ultrasound, both should be performed in all cases of mucinous carcinoma of the breast and in some equivocal cases breast MRI is of great value."
"A pure mucinous subtype carries a relatively good prognosis compared to other adenocarcinomas: 5-year survival 95% (stage 2), 75% (stage 3), 35% (stage 4). Overall the tendency to metastasise is less than for other types of cancer (e.g. invasive carcinoma of no special type). The mixed mucinous subtype has a more aggressive behaviour."