Cytologic appearance: Squamous cell carcinomas have some distinguishing characteristics that help aid in the identification of this tumor. Unlike other epithelial tumors, cells from these tumors may be more individually arranged, with angular cytoplasmic borders. Most tumors are composed of anaplastic appearing squamous cells. The cells are usually very pleomorphic, with variable N:C ratio. They contain moderate amounts of lightly basophilic to aqua-blue cytoplasm (keratinized). Some cells contain small, clear, punctate perinuclear vacuoles called keratohyalin granules. One prominent feature of squamous cell carcinomas is the presence of dysplasia and dyskeratosis, both of which indicate an abnormal cell development. Dysplasia is recognizedwhen mature, angular squamous cells, some with keratin or keratohyalin granules, contain immature nuclei. When keratin is being produced by cells with immature nuclei to a point where it is seen cytologically, sometimes compartmentalized in the cells, there is dyskeratosis (abnormal production of keratin). "Tadpole-like" cells with eccentrically located nuclei and single blunted cytoplasmic tails are occasionally seen. The nuclei are pleomorphic with coarse chromatin and prominent, multiple nucleoli. Well-differentiated SCCs may contain large numbers of fairly mature squamous epithelium. SCCs often become inflamed, making the cytologic identification of the neoplasm difficult. Unless metastasis can be identified in a regional lymph node, histological confirmation must be used to distinguish reactive versus neoplastic squamous cells.
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