74861-6

LOINC code 74861-6 identifies "Chromosome 17 copy number/nucleus in Tissue by FISH". The average number of Chromosome 17 fluorescent signals in nuclei are determined in order to calculate the average ratio of HER2 to Chromosome 17 copy number [LOINC: 49683-6]. This term is based on, but not limited in use to, the PathVysion HER-2 DNA Probe Kit, which detects amplification of the ERBB2 gene (HER2 locus) via fluorescence in situ hybridization (FISH) in formalin-fixed, paraffin-embedded human breast and gastric cancer tissue specimens. The kit contains two probes: one specific to the HER-2/neu gene locus (ERBB2 gene, 17q11.2-q12) and another targeting the alpha satellite DNA sequence at the centromeric region of chromosome 17 (17p11.1-q11.1), called CEP17 (Chromosome Enumeration Probe 17). The average number of HER2 signals [LOINC: 74860-8] along with CEP17 signals are determined by microscopic examination within the same set of nuclei. The specimen is positive for ERBB2 gene applification if the mean ratio of HER2 to CEP17 signals per nucleus is greater than or equal to 2.00.

This code measures Chromosome 17 copy number/nucleus in Tiss. It belongs to the MOLPATH class in the LOINC classification.

LOINC (Logical Observation Identifiers Names and Codes) is a universal standard for identifying laboratory and clinical observations. It is maintained by the Regenstrief Institute and used worldwide for health data exchange.