|
Tumor
|
||
|
Colon Adenoca. (75-95%)
|
=
|
+ (0-15%=)
|
|
Merkel Cell Ca.
|
=
|
+ (dot-like)
|
Follow-up Stains
|
IHC Stain
|
Comment
|
|
Expression supports colon origin
|
|
|
Expression is not typically seen in Merkel cell ca.
|
CK20 negativity in colon adenocarcinoma may be due to incomplete fixation, or in some tumors CK20 and CDX-2 loss of expression may be associated with BRAF mutations.
References
Hadi, AIMM Annual Meeting, “Carcinomas of Unknown Primary”, presentation, 2011.
Arch Pathol Lab Med. Vol 134, February 2010.