HER2 by IHC, Pan-Tumor

Formalin-fixed, paraffin-embedded (FFPE) tumor

One paraffin block or five unstained, positively-charged tissue slides cut at 4-5 microns and dried for one hour at  60°C

Three unstained slides

Paraffin block transport pouch or slide mailer

Specimen should be fixed in 10% neutral-buffered formalin. Fixation time should be between six and 72 hours according to ASCO/CAP guidelines; however, the package insert indicates optimum fixation time between 18 and 24 hours.

Maintain specimen at room temperature.

 Absence of tumor; unacceptable specimen types; non-indicated tumor types

HER2 is known to be expressed in various solid tumor types. This test is used to determine eligibility for HER2-targeted therapy in patients with any solid tumor. There is no equivalent FISH assay or FISH reflex scenario for this pan-tumor indication. For tumor types with specific test devices (e.g., breast, gastric, CRC), use of those tests is recommended instead.

Use of fixatives other than 10% neutral-buffered formalin or fixation times less than six hours or more than 48 hours may not yield reliable results.

Immunohistochemistry (IHC)

Meric-Bernstam F, Makker V, Oaknin A, et al. Efficacy and Safety of Trastuzumab Deruxtecan in Patients With HER2-Expressing Solid Tumors: Primary Results From the DESTINY-Pan Tumor02 Phase II  Trial. J Clin Oncol. 2024 Jan 1;42(1):47-58. PubMed 37870536