case_images: PMC5362847_01
case_images: Right upper lip swelling at initial examination
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case_images: A 9-year-old spayed female domestic shorthair cat was examined for a 3 month history of firm swelling of the right upper lip (Figure 1).
case_images: Right upper lip swelling 9 months after initial examination
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case_images: Nine months after initial presentation the right upper lip swelling had continued to enlarge with severe exudation and crusting (Figure 2).
case_images: Right upper lip after wide surgical excision
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case_images: General anesthesia was induced to facilitate wide excision of the affected skin and closure with an advancement flap (Figure 3).
case_images: Section of the right upper lip. Multiple epithelial cysts (crosses) invading the dermis, with surrounding severe lymphoplasmacytic, neutrophilic, and mastocytic dermatitis (hematoxylin and eosin x 2)
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case_images: Histologic examination of excised tissue demonstrated multiple cysts lined by keratinizing stratified squamous epithelium containing laminated keratin, basophilic debris, individual keratinocytes, and lymphocytes and plasma cells (Figure 4).
case_images: Thirteen months after initial examination, prior to euthanasia, demonstrating deviation of the nasal philtrum to the cat's right
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case_images: The lip swelling resulted in deviation of the nasal planum (Figure 5).
case_images: Sections of the right upper lip. (a) Nests of squamous cell carcinoma (SCC; arrow) adjacent to epithelial cyst (cross) (hematoxylin and eosin x 4). (b) Juxtaposition of epithelial cyst (black arrow), demonstrating squamous keratinization, and SCC (white arrow), demonstrating aberrant keratinocyte differentiation and necrosis (haematoxylin and eosin x 10). (c) Detail of SCC image in (b) (haematoxylin and eosin x 40)
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case_images: These features were compatible with SCC (Figure 6).