Squamous cell carcinoma
A carcinoma arising from the flat, layered cells that line surfaces exposed to wear: skin, mouth, throat, oesophagus, cervix, the larger airways. Often linked to tobacco, sun or HPV.
Squamous cells are stacked like tiles and make keratin, and their cancers keep enough of that character for pathologists to recognise them; the common causes are chronic irritation and carcinogens, which is why they dominate in smokers' airways and oesophagus, in sun-exposed skin, and in HPV-infected cervix, anus and throat. Squamous cancers share some biology across sites (frequent TP53 and CDKN2A loss, PIK3CA and FGFR1 changes) and have proven responsive to immunotherapy and, for skin, to cemiplimab. In lung cancer the label 'non-squamous' on a trial or drug label means adenocarcinoma and its relatives, and excludes squamous disease.