Thanks to the confirming post by my colleague tlspiegel-ga,
as well as input from another colleague, crabcakes-ga, who
has extensive experience in clinical medicine, I now feel
absolutely sure about my assessment, and will repost it as
an answer, with some additions suggested by crabcakes-ga.
I'm not a doctor, and the precise phrase doesn't show up in
the medical dictionaries I checked, but looking at the context
of the pages on which I found that phrase may be enough to
clarify the meaning for your purposes.
This article from the Journal of Lower Genital Tract Disease,
titled 'Investigation of Laser Cervical Cone Biopsies Negative
for Premalignancy or Malignancy', states:
"In the current study, there was a severe degree of thermal
distortion in 44% of the 59 negative cone specimens and this
precluded full evaluation. This rate is somewhat similar to
that of Mathevet et al. who in a pathological review of 37
laser cone biopsies found difficulty in evaluating 51% of
the cases because of laser-induced coagulation artifact.
Thermal artifact can be reduced by using a cold knife
technique or tonsil snare at the endocervical margin
rather than using the laser to cone the apex of the specimen."
In other fields, such as videography, the term artifact refers
to an unwanted glitch or distortion of some kind:
"An unintended, unwanted visual aberration in a video image."
This appears to match the context of the usage of the term
in the quotation above, in that a coagulation artifact is
an undesirable aberration in the manner in which the biopsy
tissue coagulates, caused by the use of the laser during the
course of a laser cone biopsy, which complicates or prevents
a full evaluation of the biopsy tissue.
This suggests to me that the results of your husband's biopsy
would be considered less conclusive than a biopsy in which
no coagulation artifacts occurred, but the doctor should be
able to tell you whether that's the case.
And, to paraphrase the input I received from crabcakes-ga:
A "thrombus" is also a clot. A coagulation artifact is indeed
a clot/coagulation "chunk", or piece, that obscures the field
when viewing a slide. Anything we see on a pathology slide that
is not supposed to be there is basically an artifact - like
threads from clothing in a urine specimen, or sediment from the
staining process that should not be there.
The following November 1999 Newsletter from Clin-Path Associates,
P.C. Pathology Specialists of Arizona, talks about slide preparation
and the possibility of errors due to clotting, or coagulation:
"This component of the procedure is as important as the aspiration
of material. Errors in slide preparation can result in a suboptimal
or nondiagnostic specimen. Material should be placed on slides
immediately to prevent clotting of the specimen in the needle hub.
Clotting of the specimen in the hub results in difficulty in
transferring the specimen to the slides. Rinsing the needle in a
rinse or tapping the hub of the needle against the slide while
holding the hub of the needle with a hemostat can aid in recovering
the clotted material in the hub. With prolonged clotting of the
specimen, the diagnostic material becomes enmeshed in a fibrin
clot. When the clotted material is transferred to the slide the
cells may be poorly visualized resulting in a suboptimal specimen."
Additional information may be found from an exploration of
the links resulting from the Google searches outlined below.
Searches done, via Google: