Atypia is a medical term for cells that appear abnormal but are not cancerous. Pathologists identify these cells by looking at tissue samples under a microscope, noting irregularities in their structure, size, or shape. Atypia is not a diagnosis of cancer. It is a signal that the body has produced cells that deviate from their normal state, warranting closer medical attention.
Understanding the Spectrum of Cell Changes
Cellular structure and growth exist on a continuum, with atypia representing a middle ground between normal and cancerous states. Healthy tissues maintain a predictable organization of cells that are uniform in size, shape, and function. The first step away from this baseline is hyperplasia, a condition where there is an increase in the number of cells, but the cells themselves retain their normal appearance.
Atypia introduces a new level of change where the cells themselves begin to look unusual. Under a microscope, a pathologist might observe that the nuclei are enlarged, irregularly shaped, or contain an abnormal amount of genetic material. The overall organization of the cells within the tissue may also appear disorderly, signaling that the normal processes regulating cell form have been disrupted.
This differs distinctly from cancer, where abnormal cells grow and divide uncontrollably. As an analogy, if normal cells are perfectly spelled words, hyperplasia is like repeating a word. Atypia is a misspelled word—recognizable but incorrect. Cancer is a jumbled paragraph where the structure and meaning are lost entirely.
Common Locations of Atypia
Breast
In breast tissue, atypia is found in the milk ducts or the lobules, which are the glands that produce milk. When it occurs in the ducts, it is called atypical ductal hyperplasia (ADH), and in the lobules, it is known as atypical lobular hyperplasia (ALH). While neither ADH nor ALH are cancer, they are risk factors that indicate a higher likelihood of developing breast cancer.
Cervix
Atypia in the cervix is identified during a Pap test. Results may show “atypical squamous cells of undetermined significance” (ASC-US), which means there are slightly abnormal cells with an unclear cause. A more concerning finding is “atypical squamous cells, cannot exclude high-grade squamous intraepithelial lesion” (ASC-H). These cellular abnormalities are linked to the human papillomavirus (HPV), though many low-grade changes resolve on their own.
Skin
On the skin, atypia presents as atypical moles, medically known as dysplastic nevi. These moles have irregular features, such as uneven borders, mixed coloration, or a larger size compared to common moles. While they can resemble melanoma, dysplastic nevi are benign. The presence of numerous atypical moles increases a person’s lifetime risk of developing melanoma.
Endometrium/Uterus
Within the uterus, atypia can occur in the endometrium, the tissue lining the uterine wall. This condition, called endometrial hyperplasia with atypia, involves the overgrowth of the endometrium with an accumulation of structurally abnormal cells. It is considered a precancerous condition with a high probability of progressing to endometrial cancer if not addressed.
Diagnostic Procedures and Follow-Up
The discovery of atypia begins with a tissue or cell sample. The specific procedure depends on the location; a Pap test collects cells from the cervix, while a skin biopsy removes a suspicious mole for examination. In the breast, atypia is an incidental finding from a biopsy performed to investigate an abnormal mammogram.
Once atypia is confirmed, the next step is careful evaluation and monitoring, an approach called “active surveillance.” The goal is to observe the cells for signs of progression. This may involve more frequent screenings, such as mammograms for breast atypia or a follow-up Pap test for cervical atypia.
This surveillance allows providers to track the cells’ behavior over time. Atypical cells may remain stable or even regress, especially if caused by a temporary factor like inflammation. The follow-up plan is tailored to the specific type of atypia and its location.
Factors Influencing Atypia and Management
Several factors can contribute to the development of atypical cells, including:
- Chronic inflammation, where a prolonged immune response leads to errors in cell division.
- Hormonal fluctuations, particularly in tissues like the breast and endometrium.
- Genetic predispositions that make an individual more susceptible to cellular abnormalities.
- Infections, such as HPV in the cervix, which can directly cause cellular changes.
Management strategies are determined by the location of the cells and the assessed risk of progression to cancer. If the risk is low, continued monitoring may be the only action needed. When the risk is higher, proactive steps are recommended, like the surgical removal of the tissue containing the atypical cells.
In some situations, risk-reducing medications may be prescribed. For women with certain types of breast atypia, medications that block the effects of estrogen can help lower their future breast cancer risk. The management approach is personalized, balancing the potential for progression against the impacts of any intervention.