Immunohistochemical detection of ROS1 is useful for identifying ROS1 rearrangements in lung cancers

Akihiko Yoshida, Koji Tsuta, Susumu Wakai, Yasuhito Arai, Hisao Asamura, Tatsuhiro Shibata, Koh Furuta, Takashi Kohno, Ryoji Kushima

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132 Citations (Scopus)


The recent discovery and characterization of an oncogenic ROS1 gene fusion in a subset of lung cancers has raised significant clinical interest because small molecule inhibitors may be effective to these tumors. As lung cancers with ROS1 rearrangements comprise only 1-3% of lung adenocarcinomas, patients with such tumors must be identified to gain optimal benefit from molecular therapy. Recently, immunohistochemical analyses using a novel anti-ROS1 rabbit monoclonal antibody (D4D6) have shown promise for accurate identification of ROS1-rearranged cancers. To validate this finding, we compared the immunostaining results of tissue microarrays (TMAs) containing 17 ROS1-rearranged and 253 ROS1-non-rearranged lung carcinomas. All 17 ROS1-rearranged cancers showed ROS1 immunoreactivity mostly in a diffuse and moderate-to-strong manner with an H-score range of 5-300 (median, 260). In contrast, 69% of ROS1-non-rearranged cancers lacked detectable immunoreactivity, whereas the remaining 31% showed reactivity mainly in a weak or focal manner. The H-score for the entire ROS1-non-rearranged group ranged from 0 to 240 (median, 0). The difference in H-score between the two cohorts was statistically significant, and the H-score cutoff (≥150) allowed optimal discrimination (94% sensitivity and 98% specificity). Similar but slightly less-specific performance was achieved using the extent of diffuse (≥75%) staining or ≥2+ staining intensity as cutoffs. CD74-ROS1 and EZR-ROS1 fusions were significantly associated with at least focal globular immunoreactivity and plasma membranous accentuation, respectively, and these patterns were specific to ROS1-rearranged cases. Although full-length ROS1 is expressed in some ROS1-non-rearranged cases, we showed that establishment of an optimal set of interpretative criteria makes ROS1 immunohistochemistry a valuable method to rapidly and accurately screen lung cancer patients for appropriate molecular therapy.

Original languageEnglish
Pages (from-to)711-720
Number of pages10
JournalModern Pathology
Issue number5
Publication statusPublished - 2014 May
Externally publishedYes


  • ROS1
  • adenocarcinoma
  • immunohistochemistry
  • lung

ASJC Scopus subject areas

  • Pathology and Forensic Medicine


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