#HematologyTweetstory 8: Auer rods! These peculiar cell inclusions are a worrisome finding, defining an immature blast cell as one of myeloid lineage… and they are also probably mis-named. This image is from a chapter I wrote for a board review book @MayoClinic circa 2007. /1 
Eponymous John Auer (1875-1948) was from Rochester, New York. He got his BS @UMich, started his medical training at @HopkinsMedicine in 1898, then moved to @RockefellerInst in 1903 where he worked on anesthesia (and also married Dr. Clara Meltzer, the daughter of his mentor.) /2
In 1906, in #AJMS, Auer described peculiar rod-shaped structures in the blood cells of a 21 y/o Spanish-American War veteran who presented to Osler’s service @HopkinsMedicine with tonsillitis and epistaxis, and was found to have anemia and leukocytosis. Their diagnosis: ALL. /3
Here are some of Auer's drawings of the inclusions... unmistakable. The bar for "publication-quality" images seems to have been a bit lower in 1906 compared to today... /4
Auer’s case was in fact previously published (!), in a case series of "Acute Lymphatic [sic] Leukemia" in @bmj_latest in 1905, by Thomas McCrae. A footnote in Auer’s report says, “Almost all of the clinical notes given in this paper I owe to the kindness of Dr. Thomas McCrae.” /5
It is pretty impressive to have written up a case report that someone else previously published, in which you got the diagnosis wrong and didn't include that someone else as an author - and yet 114 years later people are still using your name every day all across the globe.🤷♂️ /6
Thomas McCrae (1870-1935) was from Guelph, Ontario, trained at @UofT, and went to @HopkinsMedicine to work with Osler as an “assistant resident” in 1895, later joining the staff. He edited Osler’s famous textbook, "The Principles and Practice of Medicine", after Osler’s death. /7
Thomas McCrae is not as famous as his younger brother John, who also trained as a physician – and wrote a classic poem about #WorldWarI that you may have heard read earlier this month: “In Flanders Fields”. This photo is of the McCrae brothers in 1893. Tom looks like Osler! /8
The great morphologist Barbara Bain in London among others have suggested Auer rods should be called "McCrae-Auer" rods. (Here is her 2011 #AJH paper). But after a century of use, that change seems unlikely to occur./9
What actually are #AuerRods? They are linear clusters of primary/azurophilic granules, which are normal in myeloid-series cells. I don't think we know yet why they cluster in this way in AML. This nice image is from hematologyoutlines.com. /10
I always thought it was peculiar that such granules were called "azurophilic", since azure=blue (as any Italian football fan @azzurri knows!), and with typical stains they are pinkish-purple or burgundy. But the original dyes used to stain them (eg Azure A) truly were blue. /11
Azure A is an example of a #Romanowsky stain, named after Dmitri Romanowsky (1861–1921), aka Romanovsky, who was among the first to use this type of dye. Methylene blue and the Giemsa stain, still used today, are other Romanowsky stains. /12
Incidentally: what an awesome mustache Romanowsky had! It reminds me of baseball pitcher #RollieFingers. I had this Topps baseball card of Fingers in 1978. While I aspired to pitch like Ron Guidry of the Yankees, I hoped one day to be able to grow a mustache like Fingers./13
Back to hematology... Auer rods are classically most strikingly seen in acute promyelocytic leukemia #APL, as in this case., which is also an image from my old Mayo board review chapter. /14
In UK & Commonwealth countries, blasts w/ multiple Auer rods are often called "faggot cells" - an old term for a bundle of sticks, eg in this Munkácsy painting. That term is rarely used in N. America, because the word has other connotations and is often used w/ hurtful intent./15
The centrality of Auer rods in classification of #MDS is highlighted by this very nice algorithm, posted just yesterday by @smbenlazar. Not everyone agrees that Auer rods should define MDS-EB2 without increased blasts, but that is how @WHO classification is currently written./16
In most series, the presence of Auer rods in #MDS portends a poor prognosis. But in a 1993 @BritSocHaem BJH paper by Seymour et al, pts with Auer rods responded favorable to chemo (77% CR with vs 27% CR without Auer rods), so the picture is a little grey. @ASH_hematology /17End
