SQUAMOUS CELL CARCINOMA IN SITU HAVING BOWENOID FEATURES
AND A FEW OF THE ARCHITECTURAL FEATURES OF A SEBORRHEIC KERATOSIS
Bowenoid atypia, characterized by transepidermal atypia with or without dyskeratotic forms, occurs in a variety of clinical settings. These include true Bowen's disease (plaques often on non-sun exposed surfaces), bowenoid actinic keratoses (small lesions on solar damaged skin), bowenoid papulosis (genital papules), plaque type of Bowen's disease of the vulva, and erythroplasia of Queyrat (velvety red plaque on the glans penis). Each of these clinical presentations has its own peculiar associations and prognosis.

Occasionally the architecture of a lesion having this type of atypia throughout the lesion is verrucoid or resembles a seborrheic keratosis. A focus of bowenoid atypia rarely replaces part of a recognizable seborrheic keratosis. The lesion that I sign out as 'atypical keratosis' does not have true bowenoid atypia.

The conclusion that this type of atypia represents a preinvasive carcinoma is probably based on the inference that this degree of atypia is somehow more ominous than lesser degrees of atypia. Actually, with the exception of the plaque type lesions on the genitalia, invasive carcinoma is rarely associated with this type of surface atypia. Most of the invasive squamous cell carcinomas that I see arise in the background of actinic keratosis type of atypia. Perhaps we should refer to these atypical variants as 'intraepidermal neoplasia' in a manner similar to the way gynecologic pathologists deal with atypical lesions of the uterine cervix.


From an area of sun damaged skin from an adult:
 
Scan power view. Papillomatosis, fusion of acanthotic rete ridges, and pseudohorn cysts are seen. The lesion has some of the architectural features of a seborrheic keratosis. 
A low power view. Transepidermal atypia (top to bottom) is seen near the central part of the lesion. A pseudohorn cyst is present. The papillary dermis in the top of the picture is somewhat glassy and this finding is nonspecific.
A high power view of the picture above. Dyskeratotic forms and mitoses are present.
A medium  power view from another area. This area is close to the periphery of the lesion.
A composite high power view of the picture above. The degree of cytologic atypia is striking, and atypical cells near the top of the epidermis resemble atypical cells in the middle and bottom of the epidermis (transepidermal atypia).

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