Squamous Cell Carcinoma

This is a malignant neoplasm of epidermal cells which show varying degrees of keratinocyte (squamous cell) differentiation.

Gross Appearance:
•Hyperemia
•Ulcerated skin lesion progressing to invasion
•Destructive ulcerated, infiltrative tumor

Histology:
•Islands, cords and trabeculae of invasive epithelial cells
•Almost always have an association with the overlying epidermis and a breeching of the basal lamina zone
•Formation of keratin pearls (lamellae of keratin within the tumor) by the invasive neoplastic cells
•Desmosomes (intercellular bridges) can be identified between tumor cells
•Production of intracytoplasmic keratin proteins
•Cytologic features of the tumor cells are variable depending on the degree of differentiation of the cells
•Most often, the cells and nuclei are large, the nuclei are hyperchromatic, the chromatin often appears clumped
•Nucleoli vary in size and may be prominent
•Those tumors that are well differentiated show the formation of keratin pearls
•Poorly differentiated tumors may only show multifocal keratinization of individual cells
•Desmoplastic reaction in the surrounding dermis and subcutaneous tissue in response to the invasive neoplastic squamous epithelial cells
•Numerous plasma cells may be found in the stroma
•May be extensive infiltration by neutrophils, particularly in areas of keratinization

Cytology:
•Moderately large to giant-sized cells
•Round, oval, clefted or lobulated nuclei; coarse, ropy chromatin; multiple, large, often irregularly-shaped nucleoli; binucleate and multinucleate forms common
•Marked anisocytosis and anisokaryosis
•Frequent perinuclear vacuolization
•Blue to turquoise-blue cytoplasm
•Often contain evidence of acute or chronic active inflammation (therefore, clean and partially debride prior to forming a scraping for cytology smears)
•If associated with bony erosion, can see multinucleate giant cells (osteoclasts), e.g. In slide provided

Prognosis:
Good at sites where wide excision possible (ear); often recur at other sites

Breeds At Increased Risk
Breed	Odds Ratio	95% Confidence Limit	Probability
Domestic Short Hair	1.9	1.52 - 2.40	0.001

Breeds At Decreased Risk
Breed	Odds Ratio	95% Confidence Limit	Probability
Himalayan	0.4	0.13 - 0.97	0.035
Siamese	0.3	0.14 - 0.51	0.001
Persian	0.2	0.08 - 0.60	0.001

Sex Distribution (N=591)

Sex Status
Percent

Male
(46.4%)

46.4%

intact
(13.9%)

15.6

neutered
(32.5%)

30.8

Female
(53.6%)

53.6%

intact
(18.4%)

19.8

neutered
(35.3%)

33.8

(normal sex distribution)

Anatomic Location (N=575)

Site
Percent

Head 80.4

Abdomen 3.6

Neck 3.3

Forelimb 3.0

Hindlimb 3.0

Multiple 2.8

Thorax 1.7

Back 1.7

Perineum 0.3

Tail 0.2