Benign Epithelial Tumors and Proliferations

Published on 05/03/2015 by admin

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Benign Epithelial Tumors and Proliferations

Seborrheic Keratosis

• Begin to appear during the 4th decade of life and then gradually increase in number.

• Macular, papular, or verrucous; colors vary from white to black but most commonly brown.

• Typically has a ‘stuck-on’ appearance with a smooth to verrucous surface (Fig. 89.1).

Fig. 89.1 Seborrheic keratoses. A Multiple seborrheic keratoses on the back, with some in a pattern that has been likened to raindrops. B Sharply demarcated pigmented papules and plaques with a papillomatous surface and horn pseudocysts. Note the ‘stuck-on’ appearance. A, Courtesy, Kalman Watsky, MD.

• Spares the palms, soles, and mucosal surfaces.

• May resemble a melanoma clinically but has no pigment network (by dermoscopy) and has horn pseudocysts.

• Sudden appearance of multiple lesions may be associated with internal malignancy (sign of Leser–Trélat) or erythroderma; the former may also be associated with skin tags, irritated seborrheic keratoses, tripe palms, and acanthosis nigricans.

• Histopathology: a spectrum of different architectures, most commonly acanthotic, papillomatous and hyperkeratotic, or irritated (Fig. 89.2).

Fig. 89.2 Seborrheic keratoses – spectrum of histologic subtypes. A Acanthotic type with lobular hyperplasia with prominent horn cysts. B Papillomatous or hyperkeratotic type with church spires of papillomatosis and hyperkeratosis. C Irritated seborrheic keratosis. Exophytic lesion with papillomatosis, hyperkeratosis, hemorrhagic crust, and dermal inflammation. A, B, Courtesy, Luis Requena, MD; C, Courtesy, Lorenzo Cerroni, MD.

• Variants:

– Dermatosis papulosa nigra (Fig. 89.3): common in dark-skinned individuals; 1- to 5-mm hyperpigmented papules on the face.

Fig. 89.3 Dermatosis papulosa nigra. Multiple hyperpigmented papules with typical location on the cheeks. Courtesy, Luis Requena, MD.

– Stucco keratosis (Fig. 89.4): 1- to 4-mm gray-white papules on the lower extremities (especially dorsal feet and ankles) of older adults.

Fig. 89.4 Stucco keratoses. Multiple gray-white keratotic papules on the ankle and dorsal foot. Courtesy, Jean L. Bolognia, MD.

– Inverted follicular keratosis: endophytic variant of seborrheic keratosis; tan to pink papule, typically on the face of adults.

Acrokeratosis Verruciformis

• Autosomal dominant disorder; sometimes associated with Darier disease.

• Multiple, skin-colored, flat-wart-like papules on dorsal aspect of hands and feet.

• Benign neoplasm of keratinocytes showing papillomatosis with overlying hyperkeratosis in ‘church spires’.

• May have ATP2A2 gene mutation.

Clear Cell Acanthoma

• Red, shiny papule or plaque, sometimes with a peripheral collarette of scale (Fig. 89.5).

Fig. 89.5 Clear cell acanthoma. Well-demarcated, dark, red, shiny papule with a wafer-like collarette of scale. Courtesy, Luis Requena, MD.

• Favors the leg.

• Histopathology: acanthosis of characteristically well-demarcated pale or clear keratinocytes with overlying parakeratosis.

Large Cell Acanthoma

• Variably colored papule or plaque in sun-exposed sites in older individuals (Fig. 89.6).

Fig. 89.6 Large cell acanthoma. Well-demarcated, thin, pink-brown plaque. Courtesy, Luis Requena, MD.

• A variant of actinic keratosis and seborrheic keratosis.

• Histopathology: orthokeratosis overlying a thin epidermis composed of enlarged keratinocytes.

Porokeratosis

• Several different types (Table 89.1; Fig. 89.7).

Table 89.1

Types of porokeratosis.

Type	Clinical Features
Porokeratosis of Mibelli	Plaque that arises during infancy or childhood, usually on a distal extremity; usually several cm in diameter
Disseminated superficial actinic porokeratosis	Pink to brown papules and plaques with peripheral scale; arise in sun-exposed sites, especially the forearms and shins; usually measure from a few mm to 1.5 cm; in some patients, autosomal dominant inheritance
Large-sized lesions	In immunocompromised patients, especially solid organ transplant recipients
Linear porokeratosis	Streaks along the lines of Blaschko; arise during infancy or childhood Risk of development of squamous cell carcinoma
Punctate porokeratosis	1- to 2-mm palmoplantar papules; arise during adolescence or adulthood
Porokeratosis palmaris et plantaris et disseminata	Palmoplantar papules in addition to involvement of the trunk, extremities, and even mucous membranes; onset during childhood or adolescence
Porokeratosis ptychotropica	Erythematous plaque, sometimes with smaller peripheral papules, in the gluteal cleft or folds

Fig. 89.7 Porokeratoses. A Porokeratosis of Mibelli on the hand of a child. B Actinic porokeratosis in a renal transplant patient with significant solar damage. Note the narrow, elevated rim. C, D Multiple lesions of disseminated superficial actinic porokeratosis (DSAP) with obvious peripheral keratotic rims; lesions can range in color from light brown to pink. E Several streaks of linear porokeratosis on the lower extremity. F Multiple keratotic papules on the plantar surface due to punctate porokeratosis. B, C, D, Courtesy, Jean L. Bolognia, MD; F, Courtesy, Kalman Watsky, MD.

• All have a distinctive thread-like border of scale that corresponds histopathologically to the cornoid lamella (column of parakeratosis histologically).

• The most common form, disseminated superficial actinic porokeratosis (DSAP), is sometimes misdiagnosed as multiple actinic keratoses.

Inflammatory Linear Verrucous Epidermal Nevus (See Chapter 51)

• Linear, pruritic, psoriasiform (erythematous with scale) plaques, usually on an extremity.

• 75% appear before age 5 years.

• DDx: primarily linear psoriasis (see Chapter 6).

Nevus Comedonicus

• Linear plaques composed of grouped comedones; may develop inflammatory acneiform lesions.

• 50% present at birth; otherwise, generally appear before age 10 years.

• May be due to mosaicism for a mutation in FGFR2.

Flegel’s Disease (Hyperkeratosis Lenticularis Perstans)

• Rare; may have an autosomal dominant inheritance.

• Onset usually during adulthood.

• Lentil-like keratotic papules on the distal lower extremities (Fig. 89.9).

Fig. 89.9 Flegel’s disease. Scaly pink to pink-brown papules on lateral foot. Courtesy, Peter Heald, MD.

Cutaneous Horn

• Clinical term for marked hyperkeratosis arising from a papule or nodule (Fig. 89.10).

Fig. 89.10 Cutaneous horn. A This cutaneous horn arose from an actinic keratosis. B Striking column of hyperkeratosis with hyperplasia of the underlying epidermis. B, Courtesy, Luis Requena, MD.

• The base of the lesion most commonly represents an actinic keratosis, seborrheic keratosis, verruca, or squamous cell carcinoma.

Solitary Lichenoid Keratosis/Lichen Planus-Like Keratosis

• Pink to pink-brown papule or plaque (Fig. 89.11); arises in chronically sun-damaged skin, most commonly on the chest, extensor upper extremities, and shins.

Fig. 89.11 Lichenoid keratosis. Pink, flat-topped papule in a fair-skinned individual. Courtesy, Jean L. Bolognia, MD.

• Occasionally multiple.

• Clinically mimics an actinic keratosis and nonmelanoma skin cancer.

• Table 89.2 lists other solitary keratoses.

Table 89.2

Examples of other solitary keratoses.

Solitary Lesion	Histologic Features of Solitary Lesion
Epidermolytic acanthoma	Epidermolytic hyperkeratosis (also seen in epidermolytic ichthyosis and some epidermal nevi)
Warty dyskeratoma	Resembles Darier disease
Acantholytic acanthoma	Resembles pemphigus vulgaris