RET and non-small cell lung carcinoma: In many Pathology laboratories, fluorescence in situ hybridization (FISH), is often used for screening of RET gene rearrangements in patients with NSCLC, since RET immunohistochemistry (IHC) shows low sensitivity and specificity.21, 22, 23, 24 The turn-around time of the technique is short (1–2 d) and small amounts of tissue are needed.