Table 3.

Recommendations for the fixation process in the CDx‐guidance ⁷ , ¹² , ¹³ , ¹⁴ , ¹⁵ , ¹⁶ , ¹⁷ , ¹⁸ , ¹⁹

Type of cancer	Biomarkers	Target molecule	Method	Formalin fixatives	Fixation time
Breast cancer	HER2	Protein	IHC	10% NBF	6–72 h <6 h should be avoided
	HER2	DNA	ISH
	ER/PgR	Protein	IHC
Non‐small cell lung cancer	EGFR	DNA	Real‐time PCR	10% NBF	6–48 h
	ALK	Protein	IHC
	ALK	DNA	FISH
	ROS1	RNA	RT real‐time PCR	10% NBF	For surgical specimens, 18–36 h For biopsy specimens, 4–24 h
	PD‐L1	Protein	IHC	10% NBF	6–48 h
Gastric cancer	HER2	Protein	IHC	10% NBF	6–48 h
	HER2	DNA	ISH
Colorectal cancer	RAS (KRAS/NRAS)	DNA	PCR‐rSSO	10% NBF	6–48 h
Malignant melanoma	BRAF	DNA	Real‐time PCR	–	–

Note: –, not described.

Abbreviations: CDx, companion diagnostics; IHC, immunohistochemistry; ISH, in situ hybridization; 10% NBF, 10% neutral buffered formalin.