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Diagnosing Breast Cancer

  • A breast mass is identified on imaging test—a CT scan or MRI—and then biopsied
  • For diagnosing breast cancer, doctors rely on mammography, breast ultrasound, MRI, and breast biopsy
  • If breast cancer is found, the next step is determining its type and stage
  • Involves Radiology & Biomedical Imaging, Pathology


Thanks to successful breast cancer awareness campaigns, most women now understand the importance of mammography, and many even know about advanced screening technologies and treatment options. But not so many are aware that a doctor they will never see or talk to—a pathologist—is the one responsible for diagnosing their breast cancer and identifying the treatment that is most likely to be effective.

“We don’t take any of this lightly,” says Yale Medicine pathologist Malini Harigopal, MD, who specializes in making breast cancer diagnoses. The Yale Medicine Pathology Department brings deep expertise to the pathological assessment of breast cancer, she says. “In addition to having an excellent pathology team, we have pathologists who look mostly at breast pathology and are becoming more and more specialized in this area,” Dr. Harigopal says.

What is breast cancer?

When malignant cells are found in any part of the breast, breast cancer is diagnosed. The majority of breast cancers begin in the terminal duct lobular units – also known as the milk-producing glands (called lobules) – or the passages through which milk passes on its way to the nipple. Though it happens far less often, cancer can also develop in the stromal (connective) tissues, including the fatty and fibrous connective tissue in the breast. “Breast cancer may present as a mass, calcification or an architectural distortion of the breast,” says Dr. Harigopal.

How is breast cancer diagnosed?

About three quarters of breast cancer cases are first detected by mammography, which the American Cancer Society now recommends every year for women of average risk from ages 45 to 54, and every two years for women 55 and older. 

If an abnormality appears in a mammogram, additional imaging tests such as breast ultrasound or magnetic resonance imaging (MRI) will be used to determine whether a biopsy is required. At Yale Medicine, a breast biopsy is done using image guidance, and then the tissue sample is sent to the pathology lab for evaluation.

Time is of the essence in order to produce reliable results, says Dr. Harigopal. “Studies have shown that tissue samples, once removed from the patient, should reach the pathology lab within an hour,” she says. They must be fixed – processed in formalin – for the right amount of time to yield accurate results. This is especially true for assessment of estrogen, progesterone and HER2 human epidermal growth factor receptor 2 biomarkers in breast cancers.

What do pathologists look for when diagnosing breast cancer?

The first question a breast pathologist looks to answer is whether cancer is present. But the information included in the pathology report goes far beyond the “yes” or “no” diagnosis. 

“Even if the biopsy is benign, we need to ensure that the calcifications seen on imaging correlate with calcifications seen on the core biopsy pathology specimen,” says Dr. Harigopal. The earliest stage of breast cancer, which are called ductal carcinoma in situ (DCIS), are usually detected that way. If there is any discrepancy between imaging and pathology, the specialists in those two areas with then confer with each other to determine why, and then proceed with their evaluation accordingly, she says.

An initial biopsy report always has a detailed visual description of the tumor. This includes information on whether the tumor is confined within the ducts (in situ) or has breached the duct wall and invaded nearby tissue and vessels (invasive). Additional details will be studied and added to the patient’s pathology report after mastectomy and sentinel node biopsy, to determine whether the cancer has metastasized or spread to any lymph nodes.

Size, histologic grade, and lymph node status are indicators that provide valuable information about the likely outcome, says Dr. Harigopal. For example, patients who have tumors that are “well differentiated” (look more like the normal tissue that surrounds them), or that have clear margins, have better prognoses than patients whose tumors are poorly differentiated and present at the margin.

How does a pathology report guide breast cancer treatment?

Besides identifying the type of breast cancer and its stage, the pathology report includes vital information on additional tests that can help to predict how a particular patient’s breast cancer cells are likely to respond to specific treatment. For example, a hormone receptor assay examines cells for the presence of receptors for the hormones estrogen and progesterone. Receptors are proteins found on the breast cells that respond to growth signals; their presence is a sign that some therapies may work better than others. “This information is critical for survival and long-term prognosis,” says Dr. Harigopal.

Pathologists also search for genetic mutations that may respond to a targeted therapy. Not all health providers do this routinely, but Yale Medicine has the capacity to perform these tests when needed.

What makes Yale Medicine’s approach to diagnosing breast cancer unique?

We are highly focused on precise diagnosis and reliable results. “We make sure that the biopsies are done right and our molecular and histochemical labs are excellent,” says Dr. Harigopal. “We don’t take any chances when it comes to decisions that will affect the patient’s care.”

In addition to comprehensive studies and repetition to ensure accuracy, difficult diagnoses are reviewed at a daily consensus conference, where challenging cases are reviewed. These meetings serve as a “second opinion that is built into the system,” she says. “If our group doesn’t agree, we’ll send it out to another expert, if needed. The goal is to provide an accurate result for each patient.”

The team also meets weekly, as part of a multidisciplinary breast tumor board, where experts from various specialities—such as surgeons, radiologists and oncologists—meet to discuss patient management and review treatment options.

Another advantage that Yale Medicine offers is the use of standardized high-quality assays, analyses that reduce the likelihood of false positives or negative results. “In addition to a complete, detailed pathology report that is typically provided– which includes information about traditional pathologic factors such as tumor stage and estrogen receptors [ER] progesterone receptors [PR] and HER2 [human epidermal growth factor receptor 2], in all invasive breast cancers–molecular tests such as Oncotype DX are performed on some patients with ER positive breast cancers,” says Dr. Harigopal.

The steps our pathologists take ensure that every Yale Medicine patient’s cancer will be classified correctly and therefore will get the best available treatment option.