Re: What is it??? -black pigment in colon

A couple of people have pointed out problems with my recent posting about 
melanosis coli.

I was quite wrong in identifying the Fontana-Masson stain as an argyrophil 
reaction - it's an argentaffin reaction, and this difference is important. 
(The reader who pointed this out may have wished to remain anonymous.)

About the anatomic location of the pigment: I would expect the pigment to be 
in macrophages surrounding the crypts, down to and probably beneath the 
muscularis mucosae. I would expect to see few (or no) macrophages in lymphoid 
follicles, and in lymph nodes draining the colon. (Wouldn't it be nice if we 
all had digital photomicrography!)

Bob Richmond
Samurai Pathologist
Knoxville TN

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