Here are two words that can cause some serious headaches for pathology students: differentiation and dysplasia.
Both terms are graded on a scale. Cells can be anywhere from well-differentiated (pretty normal looking, and resembling the cells from which they originated) all the way down to poorly differentiated (“bad” looking, and not really resembling the cells from which they originated at all) or even anaplastic (which means that the tumor cells don’t look anything at all like the cells from which they orginated). Similarly, dysplasia is graded on a mild – moderate – severe scale.
The problem arises when you start talking about the actual characteristics of poorly-differentiated and severely dysplastic cells. Both types of cells have a lot in common:
- Pleomorphism (the cells and nuclei vary a lot in size and shape)
- Abnormal looking nuclei (really big nuclei, or nuclei with dark, “hyperchromatic” chromatin, or nucleoli)
- Lots of mitoses, and some abnormal mitoses (especially tripolar ones)
- Loss of architectural orientation (the cells are basically in a state of anarchy: they pile up on each other, they don’t respect their neighbor’s boundaries, and they don’t arrange themselves in the nice regular way that normal cells do).
So…what’s the deal? It seems like both concepts (differentiation and dysplasia) are talking about the same thing: the degree of abnormality or “ugliness” in a particular group of cells. So why have two words? Is this just some masochistic pathology terminology aimed at making us miserable?
It turns out that while the two terms/concepts are indeed getting at the same idea (how “ugly” the cells look), you use the terms in totally different contexts.
Differentiation is only used when talking about neoplastic cells. You would never say, “wow, that section of normal liver is really well-differentiated.” It’s only used to describe tumor cells, period. Also, you can use the concept of differentiation to describe tumor cells of any origin – epithelial, mesenchymal, whatever.
Dysplasia, on the other hand, is only used when talking about non-neoplastic cells – it’s never used to describe neoplastic cells. Also, you only use the word dysplasia when you’re talking about epithelial cells.
The classic example for illustrating dysplasia is cervical Pap smears and biopsies. One good thing about cervical cancer is that it is always preceded by dysplastic changes. So the epithelial cells don’t just one day turn into malignant cells: they go through long stages of mild, moderate, and severe dysplasia.
It’s really important to know this, because you can catch cervical carcinomas before they even become carcinomas. If you see an area of severe dysplasia, you can remove those cells and thereby prevent carcinoma from developing in that area. You can see a pretty clear demarcation in the photo above between dysplastic cells (on the left) and normal cervical squamous epithelium (on the right).
So to summarize:
1. Both dysplasia and differentiation are words that get at the same concept: the degree to which cells look abnormal or “ugly.”
2. You only use “differentiation” when you’re talking about neoplastic cells (and they can be neoplastic cells of any type – epithelial or otherwise).
3. You only use “dysplasia” when you’re talking about non-neoplastic cells (and they have to be epithelial cells).
Thank you so much for explaining these terms in such a way that it’s easy to understand. It was very helpful!! 🙂
Kristine,
I noticed that “Pap smear” wasn’t capitalized above, and our transcripitionists don’t capitalize it, either (I correct it before my report goes out). Ditto for “Gram stain”. I think we should continue to capitalize these eponyms to honor the originators/developers who came up with the procedures. Papanicolaou did a great service to the entire world when he developed the Pap smear, likewise Gram.
On a different but similar subject, why are genera of microorganisms not being put in italics these days–e.g., Candida in Pap smears? Are we just getting lazy? Is there a style guide for medical writers that has changed things?
Thanks for your clear explanations of Pathology concepts!
Lee Henderson, MD, FCAP
thanx great information,in simple way….
Thank you for these excellent explanations. I am a cytotechnologist and I’ve enjoyed learning about my counterparts in pathology.
thanks explaining large terms in small words
Thank you sir.It is a great information.Is it possible to differentiate between high grade dysplasia from carcinoma insitu by microscopy?
There isn’t a definitive way to do that – so many times, high-grade dysplasia and carcinoma in situ are lumped together.
Thanks…I feel pathology interesting 🙂
What about blood cells? Neutrophils are often referred to as dysplastic but they are not epithelial cells.
Hi Katie – you’re right!! You can use the word “dysplasia” to refer to unusual morphologic changes in neutrophils (as well as other hematopoietic cells). In fact, there’s a whole group of diseases called myelodysplastic syndromes. However, there’s a subtle difference in the implication of “dysplasia” when you use it with blood cells.
Typically, when the concept of dysplasia is taught, it’s in a general neoplasia block, and the example of cervical carcinoma (or lung carcinoma) is used. And those are good examples, because of the well-described, progressive dysplastic changes that precede those carcinomas.
Dysplastic changes in blood cells are a little different, though, in that dysplastic changes don’t always precede hematologic malignancies (you don’t see dysplastic changes in neutrophils before CML is diagnosed, for example). Too bad!
I hope that helps 🙂
Beautiful explanation and good sense of humor …Worth it