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Table 1. Histopathologic Features Suggestive of Possible
HER2 Test Discordance
Criteria to Consider
a
New HER2 test should not be ordered if the following histopathologic findings occur
and the initial HER2 test was negative:
Histologic grade 1 carcinoma of the following types:
• Infiltrating ductal or lobular carcinoma, ER and PgR positive
• Tubular (at least 90% pure)
• Mucinous (at least 90% pure)
• Cribriform (at least 90% pure)
• Adenoid cystic carcinoma (90% pure) and often triple negative
Similarly, a new HER2 test should be ordered if the following histopathologic findings
occur and the initial HER2 test was positive:
Histologic grade 1 carcinoma of the following types:
• Infiltrating ductal or lobular carcinoma, ER and PgR positive
• Tubular (at least 90% pure)
• Mucinous (at least 90% pure)
• Cribriform (at least 90% pure)
• Adenoid cystic carcinoma (90% pure) and often triple negative
If the initial HER2 test result in a core needle biopsy specimen of a primary breast
cancer is negative, a new HER2 test may be ordered on the excision specimen if one of
the following is observed: (Strong Recommendation; EB-H)
• Tumor is grade 3
• Amount of invasive tumor in the core biopsy is small
• Resection specimen contains high-grade carcinoma that is morphologically distinct
from that in the core
• Core biopsy result is equivocal for HER2 after testing by both ISH and IHC
• There is doubt about the specimen handling of the core biopsy (long ischemic time,
short time in fixative, different fixative) or the test is suspected by the pathologist to
be negative on the basis of testing error
a
Criteria to consider if there are concerns regarding discordance with apparent histopathologic
findings and possible false-negative or false-positive HER2 test result.
