A breast mass is an area of abnormal breast tissue detected during a physical exam or through medical imaging. While many breast masses are clearly benign, imaging sometimes identifies masses that cannot be definitively classified. These are termed “indeterminate” findings, meaning imaging characteristics are not clear enough to confirm if the mass is benign or malignant. This classification is common and does not automatically mean cancer. This article explains what an indeterminate finding signifies and the steps involved in determining its nature.
Understanding Indeterminate Findings
An “indeterminate” classification for a breast mass means its appearance on imaging (mammogram, ultrasound, or MRI) does not show features that are clearly benign or malignant. Radiologists use standardized systems like BI-RADS to categorize findings, and an indeterminate mass typically suggests further investigation. This uncertainty arises from overlapping imaging characteristics between benign and malignant conditions. For example, some benign growths may mimic cancerous lesions, or a mass might have suspicious features but not enough to be definitively malignant.
Limitations of the imaging technique itself can also contribute to an indeterminate finding. Breast density, small lesion size, or certain breast tissue types can obscure details, making full characterization difficult. An indeterminate finding is not a diagnosis of cancer. It indicates that additional information is required to determine the mass’s true nature, guiding healthcare providers to recommend further investigation for a conclusive diagnosis.
Further Evaluation Steps
Upon receiving an indeterminate breast mass finding, healthcare providers typically recommend immediate next steps to gather more information. This often involves additional or specialized imaging techniques beyond the initial screening. A diagnostic mammogram may be performed, including specialized views like magnification or focal compression, to obtain a clearer assessment of the mass’s borders and internal structures. These views increase fine detail and help differentiate unclear characteristics.
A dedicated breast ultrasound is frequently used to further evaluate indeterminate masses, as it can distinguish between fluid-filled cysts and solid masses. Ultrasound also provides additional details about the mass’s shape, margins, and internal echo pattern, important for characterization. In some cases, a breast MRI may be recommended, especially when other imaging findings are inconclusive or for high-risk individuals, as MRI offers high sensitivity for detecting breast cancer. Based on these additional images, a healthcare provider determines if the mass can be reclassified as clearly benign or if a biopsy is necessary for a definitive diagnosis.
Types of Biopsy Procedures
To definitively diagnose an indeterminate breast mass, a biopsy is often performed to obtain tissue samples for microscopic examination. One common method is a fine needle aspiration (FNA) biopsy, which uses a very thin needle attached to a syringe to withdraw fluid or cells from the mass. FNA is particularly useful for distinguishing between fluid-filled cysts and solid masses, and it can be guided by ultrasound for precise targeting. This quick procedure (10-15 minutes) usually involves local anesthesia to minimize discomfort.
A core needle biopsy (CNB) is another frequently used procedure, employing a slightly larger, hollow needle to remove small cylinders of breast tissue. This method collects more tissue than FNA, providing a more comprehensive sample for pathology analysis. CNB is often guided by imaging techniques like ultrasound, mammogram (stereotactic biopsy), or MRI to ensure accurate tissue collection, especially for masses that cannot be felt. Local anesthesia is administered, and a tiny incision may be made. After samples are taken, a small clip may mark the biopsy site for future reference.
In certain situations, an excisional (surgical) biopsy may be recommended, which involves surgically removing the entire suspicious mass along with a small margin of surrounding normal tissue. This procedure is performed in an operating room, typically under local or general anesthesia. For non-palpable masses, a wire or marker may be placed prior to surgery to guide the surgeon. The removed tissue is then sent to a pathologist for detailed examination.
Interpreting Your Biopsy Results
After a breast biopsy, tissue samples are sent to a pathologist for microscopic examination and a definitive diagnosis. Results typically fall into three main categories. A “benign” result means no cancer cells were found. This is the most common outcome, with about 75% of breast biopsies returning benign findings. Benign conditions include fibroadenomas, cysts, or fibrocystic changes. Generally, no further treatment is needed, and patients often return to routine annual screening.
A “high-risk” or “atypical” result indicates that while cancer is not present, findings suggest an increased risk of developing breast cancer in the future. Conditions like atypical ductal hyperplasia (ADH), flat epithelial atypia, or lobular carcinoma in situ (LCIS) are examples. These findings may warrant close monitoring with more frequent imaging or, in some cases, surgical excision to remove abnormal tissue.
A “malignant” result confirms the presence of cancer cells. The pathology report provides additional details about the cancer, such as its type (e.g., invasive ductal carcinoma), grade (how abnormal cells look and grow), and presence of hormone receptors or HER2 protein, which guide treatment decisions. For malignant results, treatment planning with a breast surgeon and/or oncologist typically follows to determine the most appropriate course.