Pathology of Squamous Cell Carcinoma

Study Notes

Found in light-skinned individuals with chronic exposure to UV radiation from sunlight
70% of affected individuals have outdoor occupations
Usually associated with actinic cheilosis
May arise at the site where the patient holds a cigarette, cigar, or pipe
Almost 90% of lesions are located on the lower lip

Crusted, oozing, nontender, indurated ulceration, usually less than 1 cm
Usually grows slowly
Most patients are aware of a “problem” in the area for 12 to 16 months before diagnosis
Perineural invasion may result in extension of the tumor into the mandible through the mental foramen

Dysplastic proliferation involving the entire thickness of the epithelial (carcinoma in situ)
Invasion from the basal layer to the surface or top-to-bottom by islands of tumoral cells
Invasion by irregular extension of squamous tumoral cells through the basement membrane and into subepithelial connective tissue
At the earliest moment of invasion, the adjectives superficially invasive or microinvasive are often used
Squamous cells or islands of cells proliferate within the connective tissue without attachment to the surface epithelium
The invading tumor destroys normal tissue and may extend deeply into underlying adipose tissue, muscle, or bone, which will be replaced by squamous tumoral cells
Lesional cells may breach the perineurium that encases nerve bundles (perineural invasion) or may invade the lumina of veins or lymphatics (vascular invasion)
The tumor may induce dense fibrosis (desmoplasia or scirrhous change) and the formation of new blood vessels (angiogenesis)

Rarely affects oral mucosa (0.1 to 8% of malignant melanoma)
Clinical features: brown patch or blue-black, mostly polychrome, with regular limits, slightly elevated, painless, and frequently observed around sixty on the palate and gingiva
Diagnosis is often late, with symptoms such as ulcerated and bleeding tumor nodule, loss of teeth due to underlying bone destruction, and cervico-facial lymph nodes metastasis
Perineural invasion may cause paresthesia

Most common sites: tongue (usually the posterior lateral and ventral surfaces), floor of mouth, and gingiva
Other sites of involvement (in descending order of frequency): buccal mucosa, labial mucosa, hard palate, and lips