Immunohistochemical stains used in panel:
(1) carcinoembryonic antigen (CEA), from (NKI, Amsterdam)
(2) CA 125, from ITK (Uthoorn, Netherlands)
(3) cytokeratin 7 (CK7), from Sanbio (Uden, Netherlands)
(4) vimentin (VIM), from NKI (Amsterdam)
Histochemical Score
The reactivity for each stain was quantitated using a modification of the histochemical score (after McCarty et al).
modified histochemical score =
= SUM((strength of reaction) * (percent of tumor showing reaction))
where:
• strength of reaction = 0 (negative), 1+ (mild), 2+ (moderate), 3+ (strong)
• percent of tumor expressed from 0 to 100, with total of all areas = 100
• minimum score 0, maximum score 300
Discriminant Functions
discriminant function I =
= (3.2 * (histochemical score for CEA)) - (2.4 * (histochemical score for CK7))
discriminant function II =
= (2.2 * (histochemical score for CEA)) - (3.2 * (histochemical score for CK7)) - (6.5 * (histochemical score for vimentin))
Interpretation:
• For discriminant function I, a score < 116 indicates ovarian primary; a score > 116 indicates colonic primary, with 116 indeterminate.
• For discriminant function II, a score < -41 indicates ovarian primary; a score > -41 indicates colonic primary, with -41 indeterminate.
Algorithm
If the histochemical score for CEA is > 100 AND for CK7 is < 50, then the primary is colonic.
If the histochemical score for CEA is <= 100 OR for CK7 is >= 50, AND
(1) if the histochemical score for CEA < 100 AND for CK7 > 50, OR
(2) if the histochemical score for vimentin > 20, OR
(3) if the histochemical score for CA125 > 100
then the primary is ovarian.
Else indeterminate.
Limitations:
(1) The procedure does not help if the primary is from another site.
(2) Immunohistochemical staining depends on technical factors, including the source of the antibodies.
