Clinical history: 73 year old female with mass lesion on screening mammogram.
What is the diagnosis?
Mucinous carcinoma of the breast.
Microscopically, there are islands of cells floating in pools or lakes of mucin. On higher power, the cells show only low grade atypia. For the diagnosis of pure mucinous carcinoma of the breast, greater than 90% of the total lesion must contain mucinous histology and must contain only low grade nuclear features. The differential diagnosis on biopsy is that of other mucinous lesions, such as a benign mucocele.
These lesions most frequently occur in older women and are important to recognize as they have a very good prognosis.