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Criteria: The Currency of Fundamentals by Mark A. Hurt, MD

Mark A. Hurt MD


Criterion ("criterion." Webster's Third New International Dictionary, Unabridged. Merriam-Webster, 2002. [url="http://unabridged.merriam-webster.com"]http://unabridged.merriam-webster.com[/url] (23 Apr. 2012)
1) a characterizing mark or trait
2) a standard on which a decision or judgment may be based
3) an expression by whose value varieties of a mathematical form may be distinguished
Etymology: Greek kritrion, from krits judge, from krinein to separate, decide -- more at CERTAIN
The first two definitions are applicable to dermatopathologists, but the etymology gets at the heart of the matter. It is what we do every day, perhaps a few dozen to a few score to even a few hundred times a day. It is what we look for to establish a diagnosis.
So, how do we know what to look for? How do we establish a valid criterion that leads to a diagnosis? If you introspect, you will find that when your were beginning as a resident in pathology or dermatology, you were inundated with reading material -- in addition to case work. As one who trained in pathology before becoming a dermatopathologist, I was inundated with reading and with cases from patients, the diagnosis of most I had no real clue. My teachers indicated that such and such was the diagnosis, but even they did not often know why it was the diagnosis.
Why, indeed!
Given that concepts of disease stem from separating a host of concrete, mostly perceptual data, in the case of dermatopathology, it is the actual separation of the data into their differences and similarities that occurs before the judgment, conceptually, of the data. The judgment is the diagnosis -- the end result.
But what of the separation? The separation of what?
The deeper meaning of a criterion is that it is the result of observing things in nature and separating them out into groups of a similar kind based on their differences and similarities. This is the most basic kind of observation that one makes in the beginning of his career in observing the changes in tissues under a microscope. Because it is so fundamental, the observations must be defined uniformly so as to be the "currency" of communication before one is able to reach the goal of making a diagnosis. This "currency" of language, however, is not often uniform. Because of the lack of uniformity of definition in the fields of pathology and dermatopathology, controversies develop, and, as a consequence, whole schools, that advocate a particular point of view, emerge.

Let's consider just one example. In the study of melanocytic proliferations, there is the school that advocates the terms "atypia" and "dysplasia" for a wide variety of cellular and structural findings. There is another school, a minor one, that rejects both concepts as invalid; this school advocates that classes of lesions need sharp definition based on criteria, and that the terms "atypia" and "dysplasia" preclude sharp definition of any criteria.
I am of the latter school. I argue that when one looks through a microscope, one identifies specific, concrete things. One sees cells and stroma in a variety of patterns; one identifies cells that are monomorphic or pleomorphic. The nuclei have a specific quality; the cytoplasm has a variety of colors and quantity. The terms "dysplasia" and "atypia" don't come close to stating these changes; those terms were not meant to come close. Those terms are highly abstract; therefore, they are used in a variety of ways, often with disparate meanings. In short, "dysplasia" and "atypia" are closer to diagnostic terms than terms of direct perception, yet they diagnose nothing, and they were never meant to do so. In fact, the real meaning of those terms is to express one's uncertainty about a finding.
How, then, should one use concrete findings toward developing a diagnosis? The answer is surprisingly simple, but the implementation is difficult. A diagnosis is the sum, and simplest statement, of its criteria. The implementation, however, requires identification of the fundamental elements that constitute each criterion, identification of the criteria that are relevant in a given case, and weighing whether sufficient criteria have been identified that establish a definitive diagnosis in a given case.
I can say that in the realm of melanocytic lesions, as well as all neoplasms, there are only 4 possible diagnoses: malignant, benign, malignant in conjunction with benign, and I don't know. It might be surprising to learn that, perhaps, only 3 to 4 criteria are required to establish a diagnosis in most cases. "Atypia" and "dysplasia" won't help you.
For further reading, you might be interested in a recent article by Mello-Thoms et al., who analyzed residents attempting to make diagnoses of inflammatory skin diseases. Their results are interesting, but I think it might be more interesting to analyze the results of dermatopathologists 1 year out of training vs. 10 years out vs. 20 years out. I think it might be more interesting because this spectrum of dermatopathologists would have had real world experience in rendering a diagnosis on which someone's life depends, rather than in a residency, where the wrong diagnosis will be overridden, as a rule, by an attending. The pressure of rendering a diagnosis, and taking responsibility for it, has a profound effect.
Mello-Thoms C, Mello CAB, Medvedeva O, Castine M, Legowski E, Gardner G, Tseytlin E, Crowley R. Perceptual Analysis of the Reading of Dermatopathology Virtual Slides by Pathology Residents. Arch Pathol Lab Med 2012; 136:551-562.



Recommended Comments

Dr. Phillip McKee


As always a wonderful and thought provoking blog. The problem for many of us is how we were trained, where we were trained and by whom. It is so easy for the impressionable trainee to be lead down the garden path by the so-called experts in the field. The more vocal the expert, the more likely he/she is to be believed and supposition or downright rubbish becomes absolute fact. It takes time and so much effort to be able to sort the wheat from the chaff! I too believe that tumors are either benign, malignant, malignant arising in benign or don't know. I have preached this for years and yet so many folk blur this distinction. For myself, I don't know (and often no one else does either) is the most honest diagnosis in many cases and yet folk will do anything including creating so-called new entities to avoid making this statement. I do hope that a lot of people read this blog.
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Stimulating article Dr. Hurt. As a dermpath trainee I find it very confusing when senior's often say that 'this is a melanoma, because it looks like one!'. However, I am not sure there is an easy answer to the question you have raised.

When diagnosing melanocytic lesions in particular, I find that often strict criteria are difficult to employ (or that's the way I see it). The judgement of whether an individual lesion is benign/ malignant or an 'I Don't Know' lesion is based on a permutation of factors including: epidermal consumption, mitotic rate, sometimes just the presence of ONE mitosis, presence of abnormal mitoses, apoptosis, degree of pleomorphism, whether it is random or uniform, regression, inflammation, 'invasion', pagetoid ascent, architecture of the lesion/ cells (nested vs sheets vs individual cells), variation in architecture, symmetry, circumscription, maturation with depth, presence of a benign counterpart, presence of adnexal extension (suggesting a congenital origin), Spitzoid features (epithelioid cells/ Kamino bodies/ pseudonuclear inclusions), variation in pigmentation within the lesion, LVI, perineural invasion, age of the patient, pregnancy, anti-TNF drug history, site of lesion, previous history of melanoma, previous surgery to the site and the clinical history of recent change (these are the various factors I can think of as of now!!). I haven't mentioned permutations within immunohistochemistry/ ancilliary techniques like CGH etc, that folk sometimes employ!

You mentioned in your article that just 3-4 criteria are required to establish the diagnosis of a melanoma. However for a significant number of 'difficult melanocytic lesions', I find that even highly experienced experts struggle, even when all the above criteria are taken into consideration.

It would however be wonderful if someone can formulate straightforward criteria for the diagnosis of melanoma, based on just 3-4 factors. I do wish that the criteria for the diagnosis of benign vs malignant were straightforward and algorithmic enough for a computer programmed to identify set criteria, to formulate the diagnosis based on a permutation and combination of the above factors. That is when perceptual diagnoses will stop. Is that ever going to be possible?
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Dr. Mona Abdel-Halim


This is really thought provoking,,, As Sasi said, I wish if melanoma criteria are more straightforward,,,
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Mark A. Hurt MD


To Dr. Attili's point, about the number of criteria required to come to a diagnosis, it is contextual. If you introspect and attempt to think about what your mind is doing when you come to a diagnosis, it requires more and more experience to shed off nonessential criteria and stick with the important or essential criteria. This requires considerable experience, and it is fraught with error.

For instance, with a melanocytic lesion, lineage is fundamental, so is pattern, so are cytopathological characteristics - else one cannot identify the lesion as such. Within these major criteria are extended criteria that result in the knowledge of immunostaining characteristics, genetic characteristics, etc.

So, there are basically 3 primary criteria: pattern, cytopathology, lineage; then, the extended criteria are necessary to establish the diagnosis - and sometimes one doesn't even need the extended criteria. If, however, any of the primary criteria are unknown, a definitive diagnosis is not possible in many if not most cases.

One [i]might [/i]be able to identify a melanocyte cytopathologically, but it is much more difficult to establish the diagnosis of melanoma without seeing that melanocyte in a given context.

If lineage cannot be identified, a diagnosis is not possible other than in the most general sense.

If pattern cannot be identified (eg, curettings), then it is much more difficult to establish a diagnosis, but perhaps it can be done in some cases.
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