"Atypia" is a word applied commonly in pathology and dermatopathology. It has
two principal forms of usage. The first of these refers to structural,
cellular, or nuclear abnormalities identified in sections of tissue when
observed under a microscope. The second usage refers to the lack of certainty
about a diagnosis.

If you have ever read or heard the following statement that "this is an atypical
nucleus," then you have been presented an example of the first usage. If,
however, you have rendered the interpretation of an "atypical melanocytic
proliferation," you have applied the second usage.

Dr. J. George Adami was a pathologist who practiced in Montreal at the turn of
the 20th century. In 1903, he presented his position on, what he termed,
lepedic or "rind" tumors and hylic or “pulp” tumors. He equated “atypical” with
malignancy and “typical” with benignancy. His position did not survive, and few
today know of it.

Had Adami's meaning for atypia survived intact, I think there would have been
much less confusion about criteria for diagnosis today. As it is, however, the
term is used equivocally and it leads to erroneous concepts that lesions are
“atypical,” and that they are on their way to becoming cancer -- when in fact
they are simply mimics of cancer -- or they are authentic cancers.

For some years now I have advocated dropping the term “atypia” and replacing it
with specific concrete descriptive findings, findings that one can envision by a
descriptive narrative or phrase. “Atypia” doesn't provide this, and, in fact,
it provides a confusing alternative to what should be a relatively
straightforward presentation of a problem. By the way, I offer the same
strategy for the term “dysplasia.”

The next time you are looking at a melanocytic lesion of which you are having
difficulty establishing a diagnosis, ask yourself how you would describe the
findings if you omitted "atypia” and “dysplasia.” Would you still be able to
make a diagnosis? I suspect you would -- or you would have to admit that you
weren't certain.

It's worth considering....


Reference:

Adami JG. On the classification of tumours. J Pathol Bacteriol 1903;
8:243-259.