A rare case of an EML4-ALK-rearranged lung adenocarcinoma missed by in situ-hybridization but detected by RT-PCR.

Current diagnostic approaches to detect anaplastic lymphoma kinase ( ALK ) rearrangements in lung carcinoma include in situ-hybridisation (either fluorescent - FISH - or chromogenic - CISH), immunohistochemistry (IHC), and reverse transcription PCR (RT-PCR). These methods are applied either stand-alone, or in combinations. FISH is currently regarded as the gold standard by the majority of authors,1 and a positive test is required for administration of the FDA-approved ALK-inhibitor Crizotinib. A 61-year-old woman with history of heavy smoking presented with a large pleural effusion and symptoms of increasing dyspnoea and cough. Diagnostic imaging by CT scan revealed a left upper lobe lung lesion with a maximum diameter of 33 mm (figure 1) and metastatic seed to the pleura, staged at cT3b cN0 cM1a (PLE). Pleural effusion and needle core biopsy specimens of parietal pleura were collected and investigated cytologically, morphologically and by standard IHC, resulting in the diagnosis of a CK7- and TTF1-positive lung adenocarcinoma with papillary pattern. Standard molecular …