[1860] Mucinous Carcinoma (Colloid Carcinoma) of the Lung, an Immunohistochemical and Molecular Analysis

M Zenali, N Kalhor, LMS Soto, G Roso, II Wistuba, CA Moran. The University of Texas, Houston, TX; The University of Texas MD-Anderson Cancer Center, Houston, TX

Background: Mucinous (Colloid) Carcinoma of lung is an uncommon subtype of pulmonary adenocarcinomas. Differentiating between primary pulmonary and metastatic mucinous adenocarcinoma of extrapulmonary origin, namely lower GI tract origin, can be challenging; as there is a considerable histological and immunophenotypic overlap between the two. Current study was performed to evaluate immunohistochemical profile and EGFR and KRAS gene mutation status in 12 cases of mucinous carcinoma of the lung.
Design: H&E stained sections from surgical resection of 17 cases of pulmonary mucinous carcinoma were obtained from MD-Anderson. Selection was subsequent to exclusion of five patients, found to have mucinous adenocarcinoma of extrapulmonary origin. Immunohistochemical probes were utilized for detection of: CK7, CK20, TTF-1, SP-A, and CDX2; extent of expression was assessed by light microscopy in scale of 0-4+, 0: none and 4+: more than 75% staining. Molecular analysis for EGFR, exons 18-21, was carried using dye terminator PCR sequencing method. KRAS codons 12, 13, and 61 were analyzed by pyrosequencing. All EGFR and KRAS sequence variants were confirmed by independent PCR from at least two micro-dissections, sequenced in both directions.
Results: The immunohistochemical results are listed in the table 1. Molecular analysis detected wild type EGFR sequence in all cases studied. 3 cases had KRAS mutation of codons 12 or 13.

Table 1
Case #CK7CK20TTF-1SP-ACDX2
14+2+002+
24+4+003+
34+4+1+04+
44+2+002+
54+4+1+04+
64+4+004+
74+3+004+
84+0003+
92+4+N/A0N/A
104+3+1+02+
114+2+1+02+
123+1+01+4+
N/A: not available


Conclusions: Our results indicate that the use of immunohistochemistry and clinical/radiological correlation remains the gold standard for the site of origin of mucinous carcinomas occurring in lung. Strong and diffuse expression of CK7 in colloid carcinoma of the lung can help in differentiation from metastatic mucinous adenocarcinoma of lower GI tract origin. Occurrence of mutation in EGFR tyrosine kinase domain (exon 18-21) is less frequent in Colloid Carcinoma than other lung adenocarcinoma subtypes. However, the frequency of KRAS mutation is similar to that of other lung adenocarcinoma subtypes.
Category: Pulmonary

Monday, March 22, 2010 2:30 PM

Platform Session: Section E, Monday Afternoon

 

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