Multicentric Squamous Cell Carcinoma in Situ

Multicentric Squamous Cell Carcinoma in Situ
(Bowen-like disease)

This is a malignant tumor of epidermal cells, but without invasion through the basal lamina zone. This type of squamous cell carcinoma is not associated with UV light exposure, but an association with papillomavirus infection has been noted.

Gross Appearance:
•Hyperplastic
•Erythematous
•Pigmented
•Nodular

Histology:
•Epidermis and external root sheath in affected areas is thickened and often sharply demarcated from normal epidermis
•Atypical neoplastic squamous cells
•Primarily in the basal and spinous layers and extending down the external root sheath of hair follicles
•Less frequently involve the upper levels of the epidermis
•Large, hyperchromatic nuclei
•Mitotic activity may be found in all levels of the epidermis
•Cells may have a vacuolated cytoplasm
•Hyperkeratosis, parakeratosis and hyperpigmentation of the statum corneum may be present
•Leions frequently contain abundant melanin pigment
•This tumor may progress to squamous cell carcinoma with invasion through the basement membrane and then should be classified as a squamous cell carcinoma

Prognosis:
New lesions likely to arise at other sites

Sex Distribution (N=62)

Sex Status
Percent

Male
(46.4%)

44.9%

intact
(13.9%)

8.7

neutered
(32.5%)

36.2

Female
(53.6%)

55.1%

intact
(18.4%)

13.0

neutered
(35.2%)

42.1

(normal sex distribution)

Anatomic Location (N=62)

Site
Percent

Head 50

Multiple 17.7

Abdomen 11.3

Neck 8.1

Thorax 6.5

Hindlimb 4.8

Back 1.6