Atypical hyperplasia is a term which refers to an accumulation of abnormal cells in the breast tissue. It is not cancer, but can be a pre-cancerous condition where the abnormal cells causing hyperplasia keep dividing in an uncontrolled manner. It may lead to non-invasive or invasive breast cancer in the long term.
People diagnosed with atypical hyperplasia have a higher risk of developing breast cancer in the future than those who don’t have the condition. Hence breast cancer screening and medications to lower the risk of breast cancer are recommended for women with atypical hyperplasia. However, it is worth noting that the majority of women with atypical hyperplasia never go on to develop breast cancer in their lifetime.
There are two types of atypical hyperplasia – ductal and lobular. This indicates the origin of the abnormal cells. ‘Ductal’ means the abnormal cells are detected in one of the ducts through which the breast milk travels to reach the nipple.
‘Lobular’ means the abnormal cell growth is in the lobules, which are the areas in the breast that make milk. While atypical ductal hyperplasia (ADH) increases breast cancer risk in the area where it was found, atypical lobular hyperplasia (ALH) increases the cancer risk in both the breasts.
Atypical Ductal Hyperplasia (ADH)
In ADH, the abnormal pattern of cell growth happens in the lactiferous ducts. It is not exactly a pre-cancerous condition, but is still linked to higher breast cancer risk in the future. In fact, patients with ADH have the highest probability of developing invasive cancer compared to patients with all other proliferative breast conditions.
ADH is closely related to the non-invasive malignant ductal carcinoma in situ (DCIS) and may be considered an early version of it. Both conditions indicate that the premalignant cell changes detected are at a very early stage, and the prognosis is good. On histological analysis, features of ADH closely resemble those of low-grade DCIS, but smaller in size. Two key criteria that help distinguish ADH from DCIS are:
1) there is uniform involvement of up to 2 duct spaces of the breast
2) the size of the lesion is under 2 mm
When ADH is detected, the sample tissue removed for biopsy needs to be examined under a microscope. If need be, more tissue may be excised from the surrounding area to confirm the type of abnormal cell growth. If this shows no serious abnormality, no treatment is necessary. Follow-up breast imaging and examinations can be scheduled as part of screening.
Atypical Lobular Hyperplasia (ALH)
Atypical lobular hyperplasia occurs within the breast lobules and is linked to an increased risk of breast cancer in the future. According to current breast tumor classification standards, any excess lobular epithelial cells should be classified under ‘lobular neoplasia’, which includes:
- lobular carcinoma in-situ (LCIS)
- pleomorphic lobular carcinoma in-situ (PLCIS)
Although this classification is particularly intended for pathologists, the distinction between these 3 types is usually made in the pathology reports that patients receive. However, the difference between these various types of lobular neoplasia may not be very important in terms of prognosis, treatment, or subsequent risk of developing cancer in the future. A 2003 study reported that invasive lobular carcinoma is 3 times more likely to develop in the same breast in which ALH was diagnosed than in the other breast.
Similar to ADH, in ALH treatment, microscopic examination of sample tissue reveals the cell growth pattern. Based on the results, doctors will decide if more tests are required. Follow up with imaging and physical examination is recommended.