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This article discusses a case of a rare lung tumor called stratified bronchiolar adenoma. The tumor was found in a 67-year-old woman with no history of smoking. The tumor was composed of stratified epithelial cells and was accompanied by an EGFR exon 20 insertion. Immunofluorescence analysis showed that the tumor cells in the basal area coexpressed p40 and TTF-1, while those in the apical area expressed only TTF-1. The authors argue that this tumor should be described as stratified bronchiolar adenoma rather than a squamous cell neoplasm. Further research is needed to understand the origin and clinical importance of this tumor. [Extracted from the article]

Aims An easy and rapid assay for detecting mRNA in formalin-fixed paraffin-embedded samples [ RNA in-situ hybridization ( ISH)] has been reported recently. The aim of this study was to investigate the diagnostic accuracy of RNA ISH in detecting lung adenocarcinoma ( LA) with anaplastic lymphoma kinase ( ALK) gene rearrangement. Methods and results We tested ALK RNA ISH on 11 resected LAs for which ALK fusion was confirmed by immunohistochemistry ( IHC) and/or fluorescence in-situ hybridization ( FISH). ALK mRNA expression was detected by RNA ISH in all 11 ALK-positive LAs, with a mean positive cell proportion of 68.4% (median, 75.3%; range, 3-98.8%), by counting 100 tumour cells at 10 different loci; RNA ISH did not detect ALK mRNA expression in the normal surrounding lung cells. Next, we explored the concordance between ALK RNA ISH and IHC/ FISH tests by using tissue microarrays ( TMAs) containing 294 LAs. In the TMA slides, we found five ALK-positive cases with IHC and/or FISH. The mean proportion of ALK RNA ISH-positive cells in these five cases was 75.6% (median, 82%; range, 40-94%), whereas the proportion of ALK RNA ISH-positive cells in the remaining 289 cases was 0.3% (median 0%; range, 0-15%). When the cutoff value was set at 15%, ALK RNA ISH-positive and ALK RNA ISH-negative cases were distinguishable with 100% sensitivity and specificity relative to the IHC/ FISH tests. Conclusions Our findings show that RNA ISH is useful for detecting ALK rearrangement with high sensitivity and specificity relative to conventional IHC/ FISH tests. Thus, RNA ISH, which is an easy and rapid assay, could be an alternative method to IHC and FISH. [ABSTRACT FROM AUTHOR]