[3] In the fourth revision (2004) of the WHO system (currently the world standard) Bas-SqCC is classified as one of four recognized variants of squamous cell lung carcinoma.
[5] Like other forms of lung cancer, Bas-SqCC is ultimately diagnosed after a pathologist examines a tumor sample containing viable malignant cells and tissue under a light microscope and identifies certain particular characteristics.
[6] In the case of Bas-SqCC, it is essential that both evidence of squamous differentiation (i.e., intercellular bridges, production of keratin, tonofilament bundles) and basaloid architecture (i.e. prominent peripheral palisading of cell nuclei, organoid/lobular structures) are identified to make a correct diagnosis.
[3][7] Immunohistochemical markers that have been suggested to be useful in making an accurate diagnosis of Bas-SqCC include positivity for p63 and high molecular weight keratin (i.e. 34betaE12), and lack of expression of thyroid transcription factor-1 (TTF-1).
In the last decade, it has become apparent that different variants of malignant tumors generally exhibit diverse genetic, biological, and clinical properties, including response to treatment.
Stages I and II), the decreased survival could be attributable to earlier distant metastasis appearing during the natural history of these tumors, as compared to other squamous cell carcinomas and NSCLCs in general.