What Does a Breast Cancer Pathologist Do? At Work with Hannah Wen

Memorial Sloan Kettering pathologist Hannah Wen

Hannah Wen is a pathologist and director of the Breast Pathology Fellowship.

“I am a pathologist with expertise in breast pathology,” says Dr. Wen. “This means I help diagnose breast disease, mainly breast cancer. If a person has an abnormal mammogram, they may have a biopsy. I look at that biopsy under a microscope to determine if it’s cancer and, if so, what type of breast cancer it is.

“Breast cancer is not one disease. We treat different types of breast cancer in different ways, and treatment is very sophisticated. My job is to learn about the specific features of each cancer, such as tumor type, tumor grade, receptor status, to help our team of oncologists and the patient build a treatment plan together.”

A cassette

Dr. Wen holds a single paraffin block with a tissue sample.

“A big part of the pathology process involves making what we call the “cassettes” that then become slides. Our pathology assistants [PAs] are experts at preparing tissue samples for processing. Once they receive the biopsy tissue or surgical specimen from the operating room, a PA cuts it and puts it into a plastic cassette. This is called the fixation process. Once the tissue is fixed, it is embedded in paraffin, which is wax.”

Hannah Wen next to an automatic stainer

Dr. Wen next to an automatic stainer

“The paraffin blocks are then cut into very thin sections and placed onto glass slides. The slides go into a stainer, a machine that is about as big as an oven. In this machine, a robotic arm picks up the slides one by one and dips it into various solutions to stain the cells. Without this, the cells would be totally transparent and we wouldn’t be able to see them under a microscope.

“Finally, the robotic arm puts another piece of glass on the slide and I can now view the cells under a microscope.”

Microscope with slide on it

Dr. Wen looks at a triple-negative breast cancer slide with a microscope.

“One area of my research is to look for genetic mutations of triple-negative breast cancer [TNBC] that can be targeted with a drug. For another study, I am looking to see if the drug being tested actually works, if the tumor is responding to treatment at the cellular level.”

Cabinet of pathology slides

One of Dr. Wen’s cabinets of slides. Each slide has its own barcode so no information is lost due to human error.

“I’m involved in a lot of research projects. I have a couple of cabinets in my office that are full of slides. My main interest is TNBC, which is the most aggressive type of breast cancer and has the fewest treatment options for patients.”

Hannah Wen with a pathology assistant

Dr. Wen with lab supervisor Rene Serrette

“Because we review many samples, this laboratory never closes. Our technicians are cutting, processing, staining, and sorting slides 24-7 so our pathologists can view and analyze slides efficiently. Our turnaround time for biopsy is usually 24 hours or less so that patients can get answers as soon as possible. We have an excellent team here at MSK.”


Commenting is disabled for this blog post.

I was diagnosed with breast cancer last year at 52 years old . I was High grade double negative , and negative estrogen . I had stage 0 DCIS . No radiation , no chemo and no pills to take. Any recommendations on what I can do to help prevent reoccurrence .

Dear Paige, we’re sorry to hear that you went through this, but are glad to hear you’re doing well. We recommend that you discuss your concerns with your healthcare team. Thank you for your comment, and best wishes to you.

How long are the slides kept? Are facilities required to keep them for a specified time period or does it vary by facility? I have been looking for more information on high grade DCIS in women under 30 but apparently this is very uncommon.

Dear Pam, Clinical Laboratory Improvement Amendments (CLIA) regulations require that laboratories keep histology slides for a minimum of 10 years, but according to Dr. Wen, MSK keeps them much longer. We have some samples going back to the 1990s. Thank you for your comment.

I was diagnosed in 2015 with Ducis had a mastectomy of left breast no chemo or radiation treatment was giving arimidex as medication I want to know what is receptor positive for estrogen as in my case? What's the difference with the receptor negative? I had no chemo or radiation

Dear Theresa, we’re sorry to hear about your diagnosis. When a tumor is described as “estrogen receptor positive” (sometimes also called ER positive or ER+), that means that it grows in response to the hormone estrogen. About 80% of all breast cancers fall into this category. Estrogen receptor negative tumors are not affected by estrogen. Arimidex is a drug that lowers the levels of estrogen in the body. If it was given to you as part of your treatment, that means that your tumor was most likely estrogen receptor positive. Thank you for your comment, and best wishes to you.

Hi i was wondering if because my mother was diagnosed with ER + DCIS (has been cancer free since lumpectomy) should I limit contraceptive pills?

Dear Rosalyn, we recommend that you discuss this with your doctor or another healthcare provider who is familiar with your medical history. Thank you for your comment, and best wishes to you.

Dear ma'am.. What test is done on breast cancer?
I'm pursuing a pathologist..