W. Blumenfeld et al., Utility of cytokeratin 7 and 20 subset analysis as an aid in the identification of primary site of origin of malignancy in cytologic specimens, DIAGN CYTOP, 20(2), 1999, pp. 63-66
This study was undertaken to assess the utility of combined cytokeratin (CK
) 7/20 immunoprofile determination in malignant cytologic cell blocks as an
aid to the identification of tumor primary sire of origin. Fifty-one cases
in which CK 7/20 immunocytochemistry was performed as part of rite initial
workup were retrieved. Their contribution to the final cytologic diagnosis
of tumor primary site of origin was analyzed.
CK reactivity patterns were 7+/20 - (n = 34), 7-/20 + (n = 9), 7-/20- (n =
7), and 7+/20+ (n = 1). The CK 7+/CK 20-immunophenotype was the most common
one obtained, and due to its wide expression in a number of common carcino
mas, the least informative. The second most common immunophenotype was CK 7
-/20+, which is associated with colorectal origin, and as such was very use
ful when obtained.
The CK immunoprofile was more useful in the setting of a prior carcinoma, b
eing a major diagnostic determinant in 13 cases (55%) from group 1 (those w
ith a prior history of malignancy), compared to 8 cases (29%) from group 2
(those with no prior history of malignancy).
In the setting of prior carcinoma, the CK immunoprofile is most useful when
carcinomas under consideration have different ex-peered immunoprofiles (e.
g,, CK 7+/CK 20- carcinomas, including lung, breast, ovary, endometrium, an
d others, vs. CK 7-/CK 20+ carcinomas, primarily colorectal). When similar
immunoprofiles are obtained, their usefulness is greater if they are immuno
profiles other than the most common 7+/20- pattern. Similarly in newly diag
nosed carcinomas, the CK immunoprofile either helps to narrow the different
ial diagnosis or points to a specific diagnosis. Diagn. Cytopathol. 1999;20
:63-66. (C) 1999 Wiley-Liss, Inc.