Chromogenic in situ hybridization to detect EGFR gene copy number in cell blocks from fine-needle aspirates of non small cell lung carcinomas and lung metastases from colo-rectal cancer.
BACKGROUND
Several studies demonstrated that epidermal growth factor receptor (EGFR) gene copy number (GCN) correlates to the response to tyrosine kinase inhibitors in non small cell lung cancer (NSCLC) and to anti-EGFR monoclonal antibodies (MoAbs) in metastatic colorectal cancer (CRC). In the presence of lung nodules, cytology is often the only possible diagnostic approach. Chromogenic in situ hybridization (CISH) is an alternative technique to fluorescence in situ hybridization (FISH), but its feasibility in detecting EGFR GCN in cell blocks from fine-needle aspiration cytology (FNAC) of lung nodules has not yet been established.


METHODS
We evaluated the feasibility of CISH on 33 FNAC from 20 primary NSCLC (5 squamous carcinomas, 8 large cell carcinomas and 7 adenocarcinomas) and 13 lung metastases from CRC.


RESULTS
Of the 33 FNAC analyzed by CISH, 27 (82%) presented a balanced increase in EGFR gene and chromosome 7 number: 10 cases (30%) showed a low polysomy, 15 (45%) a high polysomy and 2 (6%) NSCLC were amplified. No significant differences between NSCLC and CRC lung metastases were found in relation to disomic or polysomic status. In addition, no correlation between EGFR GCN and EGFR immunohistochemical overexpression was found. Furthermore, we compared CISH results with those obtained by FISH on the same samples and we found 97% overall agreement between the two assays (k = 0.78, p < 0.0001). Two cases were amplified with both assays, whereas 1 case of NSCLC was amplified by FISH only. CISH sensitivity was 67%, the specificity and positive predictive value (PPV) was 100%, and the negative predictive value (NPV) was 97%.


CONCLUSIONS
Our study shows that CISH is a valid method to detect EGFR GCN in cell blocks from FNAC of primary NSCLC or metastatic CRC to the lung.
Simone
Giovanni
G
Pathology Department, Giovanni Paolo II National Cancer Institute, via Hahnemann 10, Bari, Italy. g.simone@oncologico.bari.it
Mangia
Anita
A
Malfettone
Andrea
A
Rubini
Vincenza
V
Siciliano
Michele
M
Di Benedetto
Anna
A
Terrenato
Irene
I
Novelli
Flavia
F
Mottolese
Marcella
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000782:Aneuploidy; D044963:Biopsy, Fine-Needle; D001710:Biotin; D002289:Carcinoma, Non-Small-Cell Lung / Q000737:chemistry / Q000235:genetics* / Q000473:pathology; D002863:Chromogenic Compounds; D002897:Chromosomes, Human, Pair 7; D015179:Colorectal Neoplasms / Q000737:chemistry / Q000235:genetics* / Q000473:pathology; D004076:Digoxigenin; D066246:ErbB Receptors / Q000032:analysis / Q000235:genetics*; D005240:Feasibility Studies; D005260:Female; D018628:Gene Dosage; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization / Q000379:methods*; D017404:In Situ Hybridization, Fluorescence; D007558:Italy; D008175:Lung Neoplasms / Q000737:chemistry / Q000235:genetics* / Q000473:pathology / Q000556:secondary; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012189:Retrospective Studies
D002863:Chromogenic Compounds; D001710:Biotin; C512478:EGFR protein, human; D066246:ErbB Receptors; D004076:Digoxigenin