Ligation-dependent RT-PCR: a new specific and low-cost technique to detect ALK, ROS, and RET rearrangements in lung adenocarcinoma.

Detection of anaplastic lymphoma kinase (ALK), ROS proto-oncogene 1 (ROS1), and rearranged during transfection (RET) gene rearrangements in lung adenocarcinoma is usually performed by immunohistochemistry (IHC) screening followed by fluorescence in situ hybridization (FISH), which is an expensive and difficult technique. Ligation-dependent reverse transcription polymerase chain reaction (RT-PCR) multiplex technique can detect gene rearrangements using probes specifically hybridized to either side of the break point. PCR products are then sequenced by pyrosequencing or high throughput sequencing in order to identify the two genes involved. The reagent cost is <15 dollars per patient and results are available in 2 days. We have developed a 47-probe LD-RT-PCR kit especially for lung adenocarcinomas. Thirty-nine lung adenocarcinomas were studied: 24 ALK+, 14 ROS1+, and 1 RET+. ALK+ and ROS1+ were IHC+ (D5F3 Ventana for ALK and D4D6 Cell Signaling Technology for ROS1) and all cases were FISH+ (Vysis ALK Breakapart Probe Abbott for ALK, Zytolight SPEC ROS1 Dualcolor Breakapart Probe for ROS1 and Zytolight SPEC RET Dual Color Breakapart for RET); 14 wild type samples were included as negative controls. Using LD-RT-PCR, 15 rearrangements (63%) were detected in the ALK cases (gene partner: EML4 in all cases), 9 rearrangements (64%) in the ROS1 cases (gene partners: CD74 in 8 cases and SLC34A2 in 1 case) and 1 (100%) in the single RET case (gene partner: KIF5B). No rearrangement was found in the 14 negative control cases. Negative cases using LD-RT-PCR could be explained by the fact that some partner genes were not included in our assay and therefore could not be detected. Because it is an affordable, fast, and very simple technique, we propose using LD-RT-PCR when ALK immunostaining is positive. For LD-RT-PCR-negative cases, samples should then be analyzed by FISH.

[Glomus tumor of kidney: Unusual location of a rare mesenchymal tumor]. / Tumeur glomique rénale : localisation inhabituelle d'une tumeur mésenchymateuse rare.

Glomus tumors are rare mesenchymal tumors, mostly cutaneous or subcutaneous, for which visceral locations have been described. We report the case of a solid renal glomus tumor incidentally discovered in a 60-year-old patient. The tumor was 25mm wide and was mainly composed of glomus cells expressing smooth muscle actin and vimentin. These cells were negative for cytokeratin, neuroendocrine markers and renin. Glomus cells were associated with blood vessels and bundles of smooth muscle fibers. The purpose of this work is to report the diagnostic criteria, signs of malignancy and main differential diagnosis of these rare tumors whose prognosis is usually excellent after complete surgical resection.