Most breast malignancies arise from epithelial elements and are categorized as carcinomas. Breast carcinomas are a diverse group of lesions that differ in microscopic appearance and biologic behavior, although these disorders are often discussed as a single disease.
The in situ carcinomas of the breast are either ductal (also known as intraductal carcinoma) or lobular. This distinction is primarily based upon the growth pattern and cytologic features of the lesions, rather than their anatomic location within the mammary ductal-lobular system.
The invasive breast carcinomas consist of several histologic subtypes; the estimated percentages are from a contemporary population-based series of 135,157 women with breast cancer reported to the Surveillance Epidemiology and End Results (SEER) database of the National Cancer Institute between 1992 and 2001 :
Infiltrating ductal - 76 percent
- Invasive lobular - 8 percent
- Ductal/lobular - 7 percent
- Mucinous (colloid) - 2.4 percent
- Tubular - 1.5 percent
- Medullary - 1.2 percent
- Papillary - 1 percent