Aldehyde dehyderogenase (ALDH1A1) delineating the normal and cancer stem cells in spectral lung lesions: An immunohistochemical appraisal

Background and aimALDH1A1 is one of the promising cancer stem cell markers, it has been found in different cancers, including lung cancer. We aimed to assess its immunohistochemical expression in spectral lung lesions (neoplastic versus non neoplastic) and to correlate its expression with certain pathological parameters (e.g. histopathological type and tumor grade).Materials and methodsThe study included 105 specimens of spectral lung lesions (20 adjacent normal tissues, 64 non small cell carcinoma (NSCLCs), 16 small cell carcinoma (SCLCs) and six inflammatory pseudotumors, in addition to nine metastatic tumors to lymph nodes. Both H&E and immunohistochemical stained sections were assessed and evaluated according to quick immunoreactivity score.ResultsALDH1A1 expression showed a broad dynamic range of immunoreactivity score (0–8) in different types of lung cancers with strong reactivity of normal stem cells. Significant statistical associations were found between ALDH1A1 expression and squamous cell carcinoma & SCLC (p = 0.02 and 0.003, respectively), with very high mean percentage of positive cells in SCLC (58.50 ± 10.62), followed by adenocarcinoma and squamous cell carcinoma (38.37 ± 35.12 and 22.77 ± 13.89, respectively). Adenocarcinomas were classified according to the IASLC/ATS/ERS classification and grouped by architectural grade into low, intermediate and high. Heterogeneity of ALDH1A1 immunoreactivity scores within adenocarcinoma can reflect histological patterns heterogeneity with a strong association to the grade. Strong diffuse expression was seen in inflammatory pseudotumors and impressive membranous expression was noticed in metastatic tumors. Important pitfalls of ALDH1A1 immunostaining were applied for accurate interpretations.ConclusionWe ascertained the presence of strong association between ALDH1A1 expression and both histological subtype & tumor grade of NSCLCs. We report a fascinating finding; ALDH1A1 heterogeneity within adenocarcinoma can be mapped to its histological patterns. Furthermore, we elucidated its presence in SCLCs and inflammatory pseudotumors. Also a comparative image was drawn between its expressions in the primary lung tissue and in the metastatic lymph nodes.