Types of Breast Histologies

The earliest form of the disease, ductal carcinoma in situ (8500/2), comprises about 15-20% of all breast cancers and develops solely in the milk ducts. The most common type of breast cancer, carcinoma of no specific type (8500/3) (formally called Ductal carcinoma)(also referred to as mammary carcinoma), develops from ductal carcinoma in situ, spreads through the duct walls, and invades the breast tissue. Invasive ductal carcinoma accounts for about 70% of breast cancers.

Cancer that begins in the lobes or lobules is called lobular carcinoma (8520/3) and is more likely to be found in both breasts. Invasive lobular carcinoma originates in the milk glands and accounts for 10-15% of invasive breast cancers. Both ductal and lobular carcinomas can be either in situ, or self-contained; or infiltrating (invasive), penetrating the wall of the duct or lobe and spreading to adjacent tissue.

The most common histology codes for breast are
ICD-O-3 Code ICD-O-3.2 Description Notes
8500/2 Ductal carcinoma in situ
Intraductal carcinoma
Intraductal carcinoma, non-infiltrating, NOS
DCIS of Low nuclear Grade (Grade is L)
DCIS of intermediate nuclear Grade (Grade is M)
DCIS of high nuclear grade (Grade is H)		 See the Solid Tumor Rules, under Reporting Guidelines, Breast for additional subtypes
8500/3 Infiltrating duct carcinoma, NOS
Invasive breast carcinoma of no special type
Invasive breast carcinoma, NOS
Infiltrating duct carcinoma, NOS		 See the Solid Tumor Rules, under Reporting Guidelines, Breast for additional subtypes
8520/3 Lobular carcinoma, NOS
Invasive Lobular carcinoma		 See the Solid Tumor Rules, under Reporting Guidelines, Breast for additional subtypes
8520/2 Lobular carcinoma, in situ
Lobular neoplasia
Classic lobular carcinoma in situ
Florid lobular carcinoma in situ		 See the Solid Tumor Rules, under Reporting Guidelines, Breast for additional subtypes

See current version of the Solid Tumor Rules under Reporting Guidelines and section “General Instructions” for additional information on the Solid Tumor Rules.

Updated: January 10, 2025