Pathology of different benign and malignant lesions of the breast

Diagnosis of Breast Cancer

The treatment of breast cancer is a multidisciplinary team effort, and the role of the pathologist is to determine the correct diagnosis. The majority of breast cancers are first detected on abnormal screening imaging, such as mammography, magnetic resonance imaging (MRI) or ultrasound. The type of radiographic imaging used depends upon the patient's age and the characteristics of the breast tissue such as how fibrous or fatty the breast tissue is.

When a mass or a radiographic abnormality is detected, a tissue sample must be obtained to determine the correct diagnosis. The pathologist evaluates the tissue to determine if it is benign or malignant (cancerous). Not all masses that are detected by imaging are cancer; some breast masses are benign tumors such as fibroadenomas. Different types of methods may be used to get a sample of breast tissue to submit to the pathologists for evaluation. These methods include fine needle aspiration (FNA), core needle biopsy, and excisional biopsy. An FNA consists of using a fine needle to pull out (aspirate) cells from the lesion. A core needle biopsy consists of a small needle that takes a thin core of tissue out of the mass; this is often done under radiographic guidance by interventional radiologists. A core needle biopsy is the most common type of specimen obtained for initial evaluation of a breast mass or radiographic abnormality. Excisional biopsies consist of removal of a larger amount of tissue, such as 2x2cm, than is removed with a core needle biopsy; these are performed by surgeons in an operating room.

The decision of what method to use is influenced by the characteristics of the mass as well as the patient's breast tissue. For instance, a lesion which appears to be a simple benign cyst may be aspirated by FNA. Masses which are superficial or easily accessible may be sampled by core needle biopsy. If a mass is very deep in the breast, such as adjacent to the chest wall, it may be too deep to be reached by a needle biopsy. In these cases, excisional biopsy may be the only way to sample the tissue.