This tumor has cells which are poorly differentiated. Note the many layers of flattened, eosinophilic cells that occupy 80% or more of this specimen. The marked eosinophilia of the cells is due to the presence of large amounts of cytoplasmic keratin . This is a characteristic specimen of squamous cell carcinoma. This type of cancer typically arises in the central (hilar) portion of the lung and has the closest correlation with smoking of any of the bronchogenic cancers.