Tutorial on Breast Pathology Part I: Ductal and Lobular Neoplasias Thomas J Lawton MD, Director Seattle Breast Pathology Consultants, LLC Seattle, WA

There are two main types of epithelial cells in the breast: Ductal and Lobular. The distinction is based on how the cells look and how they grow, not necessarily on their location in the breast. So ductal cells can travel into the lobules and lobular cells can travel up the ducts.

Normal breast duct and lobules lobule duct lobule

Let’s start with ductal….

There are three main ductal lesions: 1) ductal hyperplasia, usual type; 2) atypical ductal hyperplasia; and 3) ductal carcinoma in situ Ductal hyperplasiaAtypical ductal hyperplasiaDuctal carcinoma in situ

Ductal hyperplasia, usual type This basically means there are too many ductal cells in the ducts but they are not atypical. Often graded as mild, moderate, or severe (florid). Studies show there is an increased relative risk (1.5-2 times) for the subsequent development of invasive carcinoma with moderate to florid ductal hyperplasia. This risk applies to both breasts.

Ductal hyperplasia: What does it mean if my biopsy shows this? If found on core needle biopsy and the findings are concordant to the radiologist, no need for surgical excision. If found on a surgical excision and nothing more significant is found, no need for the pathologist to comment on margins and no need for surgical re-excision.

Atypical ductal hyperplasia This term describes a proliferation of ductal cells that has “some, but not all” of the features of low grade ductal carcinoma in situ. Studies show there is an increased relative risk (4- 5 times) for the subsequent development of invasive carcinoma. This risk applies to both breasts.

Atypical ductal hyperplasia: What does it mean if my biopsy shows this? If found on core needle biopsy, surgical excision is warranted because of an approximate 20-30% chance of finding carcinoma in situ or invasive carcinoma based on most studies. If found on a surgical excision and nothing more significant is found, no need for the pathologist to comment on margins and no need for re-excision in the vast majority of cases.

Ductal carcinoma in situ This term refers to a neoplastic proliferation of ductal cells that has not invaded beyond the confines of the duct. Studies show there is an increased relative risk (8- 10 times) for the subsequent development of invasive carcinoma. This risk applies to both breasts. However…… (next slide)

Ductal carcinoma in situ is also thought to be a PRECURSOR lesion to invasive carcinoma! This means most studies have shown that, if left untreated, ductal carcinoma in situ can progress to invasive carcinoma

Ductal carcinoma in situ: What does it mean if my biopsy shows this? If found on core needle biopsy, surgical excision is necessary. If found on a surgical excision, the size of DCIS, nuclear grade, presence of necrosis, and distance from all surgical margins should be reported by the pathologist. If margins are close, additional surgery may be needed. Radiation therapy may also be needed. In many cases, a medical oncologist may ask the pathologist to determine if the DCIS is estrogen receptor positive.

Now on to lobular…

Lobular hyperplasia Not a well-defined pathologic term Diagnosis not generally used

Atypical lobular hyperplasia A proliferation of small cells that begin to fill up but do not expand the milk-producing glands in the lobules. Studies show there is an increased relative risk (4- 5 times) for the subsequent development of invasive carcinoma, similar to atypical ductal hyperplasia. This risk applies to both breasts.

Atypical lobular hyperplasia: What does it mean if my biopsy shows this? If found on core needle biopsy, most doctors will recommend a surgical excision but this is somewhat controversial. If found on a surgical excision and nothing more significant is found, the pathologist does not need to comment on surgical margins, and no surgical re-excision is needed.

Lobular carcinoma in situ A proliferation of bland cells that fill up and expand at least 50% of the milk-producing glands in the lobules. Studies shows there is an increased relative risk (8-10 times) for the subsequent development of invasive carcinoma. This risk applies to both breasts.

Lobular carcinoma in situ

Lobular carcinoma in situ: What does it mean if my biopsy shows this? If found on core needle biopsy, most doctors will recommend a surgical excision but this is somewhat controversial. If found on a surgical excision and nothing more significant is found, the pathologist does not need to comment on surgical margins, and no surgical re-excision is needed.

Stay tuned for Part II which will cover invasive carcinomas…