​'The doctor’s doctor​': How pathologists help diagnose disease and find the best treatment

Pathologist Jeffrey Mueller, MD, and Charlene Gettings, manager of the anatomic pathology lab, review slides of tissue samples
Pathologist Jeffrey Mueller, MD, and Charlene Gettings, manager of the anatomic pathology lab, review slides of tissue samples 

A pathologist plays a crucial role in medical care. Sometimes called “the doctor’s doctor,” they help the treating physician diagnose a patient and pinpoint the best course of treatment. But since pathologists tend to work behind the scenes, the average patient may not realize what they do, which can cover everything from testing blood samples to molecular genetics research.

Daniel Arber, MD, chair of the Department of Pathology at the University of Chicago Medicine, is one of two UChicago Medicine pathologists (out of three total) named to Chicago magazine’s 2018 list of the region’s top doctorsAnthony Montag, MD, an expert in gynecologic and soft tissue pathology was the other UChicago Medicine pathologist on the list. We spoke to Dr. Arber about the traditional role of the pathologist, how that’s changing in the era of precision medicine and what makes UChicago’s pathology program unique.

What's the traditional role of a pathologist?

It's evolving. As a pathology department, we're both a basic science department and a clinical department. Almost a third of our faculty just do basic science research, and the other two-thirds do clinical work that ranges from everything from overseeing the clinical labs and all the associated tests to anatomic pathology. They process specimens from the operating room, look at slides and make the diagnosis for biopsies and resection specimens. We do some autopsies as well, but that's a very small component of what we do.

So traditionally in a hospital-based setting, pathologists have been viewed as people who make a diagnosis based on just looking at the specimen slides. But now we do a lot of other things like immunophenotyping studies and molecular genetics studies. We run all those laboratories, not only to make the diagnosis, but to provide the information that can help with targeted therapy and prognosis for the patients. So, we work closely with surgeons, oncologists, hematologists and all the medical specialists.

Does the average patient understand the role the pathologist plays?

I think patients usually assume that the doctor they saw figures it all out. Or they think it's a black box, like a machine that you can just stick the tissue into and the result comes out. Most people just don't understand what pathologists do because their impressions are based on what they see on television, which is more forensic work.

How do you describe the pathologist's role?

Some people have referred to it as being "the doctor's doctor" because we actually explain to the doctors what the diseases are. That's a little condescending though [laughs]. As other areas have been specialized all throughout medicine, the treating physicians understand diseases very well, and then they demand that the pathologists sub-specialize as well. We have to have people who are experts in just about all the organ systems to make sure they're up to date and they're providing the same information to the treating physicians.

At what point do you become involved in a patient's care?

There are different ways. One is if they're having a biopsy of a tumor, it automatically comes to us and we work with them. Then we present it to the tumor board, where a team of physicians discuss the case, and work directly with the treating physician. If the patient was diagnosed at another hospital and comes here, they usually bring their slides with them, and then we look at those to render our diagnosis. Anywhere from 5 to 10 percent of cases that are diagnosed elsewhere, when they come to an academic medical center the diagnosis is changed. So, that has a big impact.

The other area where we intersect with patient care is if they need a fine-needle aspiration, where we use a needle to take a small sample of cells. The surgeon or the treating physician will call a pathologist to do that. They give a quick, preliminary diagnosis, and then render a final diagnosis a day or two later. Also, when surgeons remove tumors or tissue in the operating room, a lot of times they need to know if they got all of it, or they need to confirm what they removed. So, in that case we do what are called frozen sections, which are rapid diagnoses while they're waiting in the operating room.

Pathologist's assistant Rachel Poon measures a cardiac tissue sample
Pathologist's assistant Rachel Poon measures a cardiac tissue sample

How is the field changing?

The biggest area is molecular genetics and genomics. For almost all tumors now, we do a big genomic panel, which screens for over 1,200 genes. We save all that data, but we report back to the treating physician the results of genes that are known to impact the diagnosis or prognosis of the patient. Since we have all the data stored, if a new gene is discovered to be relevant to disease, we can also go back and re-analyze the data.

Some gene mutations are targeted for therapy, and some are for prognosis. I'm a hematopathologist, so I work with leukemias and lymphomas. In leukemia, there are some gene mutations that determine markedly different prognosis than other genetic changes in the same leukemia. It looks the same under the microscope but once you know the genetics you can better predict whether it's going to respond well or poorly to treatment. There are a few genetic changes in leukemia that have a completely different therapy. Lung cancer also has different therapies that are known to work with some genetic changes but don't work with others. So, knowing that information keeps you from wasting expensive drugs on tumors that aren't going to respond and getting patients straight to the right drug if they are going to respond.

What makes the pathology program at UChicago Medicine unique? 

We have the most comprehensive genomics testing of any pathology department in the Chicago area. We do the testing here instead of sending it to outside labs, so when we go to tumor boards we can actually explain the results to the treating physician. If there's any kind of question, the surgeon and the oncologist can call the molecular pathologist, and they go over the cases with them and explain what the findings are, because the data can be very confusing when you get the reports back from outside companies.

That's something that stands out here. It also helps our research efforts, because having all of the molecular data on those tumors makes us easy collaborators with our clinical colleagues who might want to mine that data for their studies.

What's the future direction for pathology?

Sub-specialization is becoming standard. Most of our trainees sub-specialize, or they focus on a limited number of areas when they get their first job. Most of our pathologists do at least two specific fields just so we have enough expertise on all the different areas. It's that and integrating these ancillary tests, particularly molecular genetics, into the diagnosis and helping translate that for the treating physicians. It’s getting overwhelming for anyone to know all of it, so as our pathologists sub-specialize they become experts for other pathologists and physicians in the community who need help diagnosing difficult cases. That’s where we can make the greatest impact.

Daniel Arber, MD

Daniel Arber, MD

Daniel Arber, MD, is the Donald West and Mary Elizabeth King Professor and Chair of the Department of Pathology. His research focuses on molecular genetic and immunophenotypic changes in blood cancers.

Learn more about Dr. Arber