Differentiation of pulmonary from colonic adenocarcinoma by cytokeratin immunostaining

Differentiation of pulmonary and colonic adenocarcinomas1:

	n	CK7+	CK20+	CK7+/CK20-	CK7-/CK20+	CK7+/CK20+	CK7-/CK20-
primary lung carcinoma	50	94%	6%	88%	0	6%	6%
metastatic carcinoma from a lung primary	24	96%	13%	93%	0	13%	4%
total for lung carcinoma	74	95%	8%	86%	0	8%	5%

primary colon carcinoma	51	16%	96%	0	80%	16%	4%
metastatic carcinoma from a colonic primary	26	31%	100%	0	69%	31%	0
total for colon carcinoma	77	21%	97%	0	77%	21%	3%

Neither CK7 nor CK20 alone reliably differentiated pulmonary from colonic carcinomas. However, the combination is reliable, with tumours that are CK7+/CK20+ or CK7-/CK20- being of indeterminate origin.

References

1Loy TS, Calaluce RD. Utility of cytokeratin immunostaining in separating pulmonary adenocarcinomas from colonic carcinomas. Am J Clin Pathol 1994;102:764-767.