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My First Eosinophil

December 30, 2021
David Steensma, MD
Edward P. Evans Chair in MDS Research and Institute Physician at the Dana-Farber Cancer Institute; Associate Professor of Medicine at Harvard Medical School; Editor-in-chief of ASH Clinical News

When a shocking historic event occurs, many can remember exactly where they were and what they were doing when they heard the terrible news. I, too, can recall intimate details of awful incidents like the September 11th attacks or the Space Shuttle Challenger disaster.

But I also remember times when I was surprised by joy – startled out of day-to-day routine by unexpected grandeur, startled into a sense of wonder.

For instance, I remember not only where I was but what I was wearing and what song was playing on the car radio when I first saw the Northern Lights open up in the sky in front of me as I drove down a dark rural highway in northern Michigan. The aurora's shimmering curtains of green light were so spectacular that I pulled over to the side of the road, walked into a cornfield, and – to the distant sounds of Paul Simon's Graceland – watched the sky for as long as I could stand the frigid December air. It was not nearly long enough, due to the threadbare teal L.L. Bean parka I was wearing at the time.

Another memorable highlight was the first time I bit into the succulent meat of a fresh lobster, plucked from the sea just minutes before it appeared steaming on a paper plate at a roadside picnic table during a childhood late-summer vacation in Maine. I had never tasted anything quite like it. A glimpse of the rare “green flash” at sunset, a lunchtime spent watching the improbable aerial dance of a hummingbird at a backyard feeder, and, in retrospect, a far too close encounter with a grizzly bear while camping in Alaska were also undeserved gifts from the Universe.

One of the best surprises of all was the first time I saw an eosinophil.

I was a first-year medical student at the University of Chicago when it happened. Our class had just begun the hematology block of a basic histology course. As a lab exercise, I dutifully pricked my finger with a lancet, spread the blood on a glass slide under the watchful eye of a lab tech, and stained the smear with a pair of dyes that we had been sternly warned not to spill on our clothes. Once the slide dried, I slipped it onto my rented microscope and started to search for each of the cells listed on a purple mimeograph handed out by the teacher's aide, using the classic Wheater's Functional Histology textbook as a guide.

I quickly checked off all the assigned objects except one: an eosinophil. In the next few minutes, I am sure I was as much of a nuisance to the course director, James Vardiman, MD, as an impatient child in the back seat of a car asking, "Are we there yet?"

I spotted a granulocyte that seemed to have a few more burgundy granules than others and raised my hand.

"Um, Professor Vardiman, is this an eosinophil?"

He bent down and looked. "No, that's a neutrophil."

A moment later, my hand shot up again: "Okay, how about this one – an eosinophil?"

Another patient look through the lens. "No, that's a neutrophil, too."

Then, certain I’d finally hit the jackpot: "What about this other one? It seems really red."

He offered a quasi-compliment: "David, you're really good at finding over-stained neutrophils."

Finally, after what seemed like an eternity of painstaking searching, when I was ready to assign eosinophils to the same crypto-category as Bigfoot, Mel's Hole, and Mr. Snuffleupagus, I saw it.

There was no mistaking it for anything else. The eosinophil was so much better in real life than the one pictured in Wheater's. Red enough to make Stalin blush, its granules glowed in the microscope's halogen lamp as brilliantly as theater Exit signs, and its two thick nuclear lobes bulged like chewed Dubble Bubble. It was an awesome, stunning sight. I didn't even need to ask Prof. Vardiman to confirm it.

Back in the classroom the following day, I listened as John Ultmann, MD, gave an introductory lecture to hematology that was worthy of a TED talk. I found his sweeping overview of the field – from sickle cell disease to leukemia, drawing on anthropology and genetics, and invoking ghosts from Virchow to Von Willebrand – absolutely inspiring. That day, I finally knew what I wanted to do with my life. My career decision – instant, never once regretted, inflamed by an eosinophil – was to become a hematologist.

John died in October 2000 – ironically, of complications of one of the diseases he studied, lymphoma. He was a strange, curious person, yet so charismatic, full of interesting stories and passion for his life's work. Over the years, I've met several others whom John "converted" to hematology and have wondered how many of us have made career choices based as much on the passion of a gifted teacher or role model as interest in the discipline itself.

I hadn't always known I wanted to go to medical school, let alone what field to specialize in. I studied physics and astronomy as an undergraduate, which was fascinating and mind-expanding, but not very lively. When I was 19 years old, I had the best job I've ever had (and probably ever will have): running the astronomic observatory at Calvin College in Michigan. My role, similar to the teachers in histology class, was to help students in introductory courses use the observatory's telescopes to find an assigned list of astronomical objects: a planet, a nebula, a galaxy, and so on. After the observatory closed at night, I could do my own research in spectroscopy, and I often got so involved in what I was measuring that I lost track of time and was surprised to see a pre-dawn glow in the East.

Since this was Western Michigan, lake-effect clouds and poor visibility meant that most winter nights the observatory closed up, and I learned that an empty observatory is also a great place to study or, alternatively, to hang out with girls and conduct other types of research.

The sense of wonder that I saw in most of the students who came to the observatory was the same jaw-dropping awe that I felt when I first saw that amazing eosinophil. Not a night went by without at least one, "Wow!" or "Holy cow!" or "Awesome!" from a person looking into an eyepiece. (And sometimes a "Dude, that is totally radical!" – it was the 1980s after all). One student memorably burst into tears the first time she saw the spectacular M57 Ring Nebula in the constellation Lyra. "I've had such a bad day, but now, looking at that, it all seems like nothing," she said, echoing sentiments Tennyson described in his poem "Vastness" a century earlier: What is it all but a trouble of ants in the gleam of a million million of suns?

Morphology is still central to hematology, but it is losing primacy. In this age of flow cytometry and molecular genetics, we've come to distrust the meaning of cells that we see with eyes aided only by a lens. It is still important to look for eosinophils, but when the blood teems with too many of them, it is equally critical to know whether their presence is accompanied by an imatinib-sensitive rearrangement of the platelet-derived growth factor receptor.

I still enjoy sitting at the multi-headed microscope and bringing students to come look at slides. Last month, when I was attending on a hospital service, the residents, students, and I broke away from rounds for a field trip to the special hematology lab to look at various leukemia and myelodysplasia cases. Among other highlights, we saw a macrophage with 12 developing erythroid cells encircling it: It looked like a sow giving milk to a dozen piglets.

One of the most promising students exclaimed, "Whoa, that is the coolest thing I've ever seen on a slide!" I knew exactly how she felt.

May your day include a sense of wonder.

The content of the Editor's Corner is the opinion of the author and does not represent the official position of the American Society of Hematology unless so stated.

Have a comment about this editorial? Let us know what you think; we welcome your feedback. Email the editor at


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