Precancerous cells in the breast represent a significant finding that places a patient on a spectrum of elevated risk for developing invasive breast cancer. A diagnosis of precancerous cells is not cancer itself, but rather a warning sign identified through microscopic examination of breast tissue. These cellular changes indicate that the normal, orderly growth pattern of cells within the breast’s ducts or lobules has been disrupted. This finding often prompts enhanced surveillance and risk-reduction strategies.
Understanding the Spectrum of Atypia
The breast is composed of a system of ducts and lobules. Precancerous conditions arise when the epithelial cells lining these structures begin to grow abnormally, a process broadly termed hyperplasia. When proliferating cells look relatively normal under a microscope, it is classified as usual hyperplasia, which carries a slightly elevated risk for future breast cancer.
Atypical hyperplasia, or atypia, represents the next step on this continuum. It is characterized by cells that not only overgrow but also appear structurally disorganized, or “atypical.” These atypical cells show some, but not all, features of non-invasive cancer. The presence of atypia significantly increases the lifetime breast cancer risk by three to five times compared to the general population.
Pathologists closely examine the extent of this cellular disorganization to classify the abnormality. This classification determines the specific type of precancerous lesion and guides subsequent medical management.
Specific High-Risk Breast Lesions
Precancerous findings are categorized based on whether the atypical cells are located in the ducts or the lobules. These lesions are not invasive, meaning the abnormal cells have not broken through the basement membrane separating the ducts and lobules from the surrounding breast tissue.
Atypical Ductal Hyperplasia (ADH)
Atypical ductal hyperplasia (ADH) involves the disorganized overgrowth of atypical cells confined to the milk ducts. This moderate-risk lesion typically increases a person’s lifetime risk of developing breast cancer by about four to five times. ADH cells share many microscopic features of low-grade ductal carcinoma in situ (DCIS) but do not meet the size criteria for a DCIS diagnosis. Because ADH can be found alongside more significant disease, a diagnosis on a needle biopsy often leads to a recommendation for surgical removal of the surrounding tissue.
Lobular Carcinoma In Situ (LCIS) / Lobular Neoplasia
Lobular Carcinoma In Situ (LCIS), often grouped with Atypical Lobular Hyperplasia (ALH) under the term lobular neoplasia, affects the lobules, the milk-producing glands of the breast. Despite the term “carcinoma,” LCIS is not considered a true cancer but a significant marker for an elevated risk of developing invasive breast cancer in either breast. Individuals with LCIS have a seven to ten times greater likelihood of developing invasive breast cancer compared to the average population. This lesion signifies a widespread susceptibility to cancer development throughout the breast tissue.
Ductal Carcinoma In Situ (DCIS)
Ductal Carcinoma In Situ (DCIS) represents the most advanced form of premalignancy and is classified as a non-invasive, or Stage 0, breast cancer. In DCIS, the abnormal cells are entirely contained within the milk ducts, having not yet broken through the duct wall into the surrounding fatty tissue. Because DCIS carries a risk of progression to invasive cancer if left untreated, it is managed as a malignancy rather than a high-risk marker.
DCIS is graded based on cellular appearance and division rate; high-grade lesions carry a greater potential for becoming invasive. This condition is typically detected on a screening mammogram through the presence of tiny calcium deposits, known as microcalcifications.
How Precancerous Cells Are Identified and Assessed
Precancerous cells are most often discovered incidentally during diagnostic procedures or routine screening, such as mammography. Since these lesions rarely cause a lump or other noticeable symptoms, they may also be found during an ultrasound or magnetic resonance imaging (MRI) examination.
A definitive diagnosis requires a tissue sample obtained through a core needle biopsy. A small amount of tissue is removed from the suspicious area and sent to a pathologist for microscopic evaluation. The pathologist determines the specific classification of the lesion, distinguishing between benign changes, atypical hyperplasia, and non-invasive cancer like DCIS.
Risk stratification is a crucial part of the assessment, particularly for DCIS. Pathologists analyze the grade and size of the cells, and whether they express hormone receptors, such as estrogen receptors. These factors help predict the likelihood that the lesion could progress to an invasive cancer or recur after treatment.
Treatment and Long-Term Surveillance Strategies
Management for precancerous breast lesions is highly individualized and focuses on reducing the future risk of developing invasive cancer. For high-risk lesions like ADH, surgical excision, such as a lumpectomy, is often recommended to ensure complete removal and rule out hidden invasive cancer. For select patients with low-risk ADH, active surveillance with enhanced imaging may be an alternative approach.
Lesions like classic LCIS and ALH are typically managed with enhanced surveillance. This includes more frequent clinical breast examinations every six to twelve months and annual diagnostic imaging, often alternating between mammograms and breast MRIs.
For DCIS, which is considered a Stage 0 cancer, treatment is more definitive, involving surgical removal through lumpectomy or mastectomy. Risk-reduction medications, known as chemoprevention, may be offered to patients with high-risk markers like ADH or LCIS, or those treated for DCIS. Medications such as Tamoxifen or Raloxifene can significantly lower the incidence of future estrogen receptor-positive breast cancers.