Differentials
Flat warts
SIGNS / SYMPTOMS
Flesh-colored, flat-topped, slightly raised papules.
Usually multiple and found on the extremities or face.
INVESTIGATIONS
No differentiating tests.
Palmoplantar warts
SIGNS / SYMPTOMS
Palmoplantar warts are endophytic and occasionally tender, with scale and black dots on the surface, and are commonly found on the palms and soles.
INVESTIGATIONS
No differentiating tests.
Seborrheic keratosis
SIGNS / SYMPTOMS
Lesions are grayish-brown, stuck-on, scaly papules with white pseudocysts and a smooth or rough surface.
Many are present in the same skin area and persist indefinitely.
INVESTIGATIONS
No differentiating tests.
Acquired digital fibrokeratoma
SIGNS / SYMPTOMS
Lesions occur on the digit, and have a firm, smooth surface.
There are no tiny black dots on the surface.
INVESTIGATIONS
No differentiating tests.
Clavus
SIGNS / SYMPTOMS
Lesions occur on the digit in the areas of friction and over bony prominences and have a firm, rough surface.
There are no tiny black dots on the surface.
INVESTIGATIONS
Skin biopsy shows hyperkeratosis and parakeratosis with central epidermal atrophy, plus peripheral acanthosis and possible perivascular infiltrates of the upper dermis.
Callus
SIGNS / SYMPTOMS
Lesions occur on the digit in the areas of friction and over bony prominences and have a firm, rough surface.
There are no tiny black dots on the surface.
INVESTIGATIONS
Skin biopsy shows hyperkeratosis.
Squamous cell carcinoma
SIGNS / SYMPTOMS
Nonhealing, enlarging, hyperkeratotic papule that becomes inflamed and tender.
INVESTIGATIONS
Skin biopsy shows parakeratosis, atypical keratinocytes with or without koilocytes.
There may be clusters of atypical keratinocytes invading the basement membrane to form small clusters in the papillary or reticular dermis.
Human papillomavirus-related Bowen disease
SIGNS / SYMPTOMS
Nonhealing, enlarging, hyperkeratotic papule that becomes inflamed and tender. May occur around the nail apparatus, as well as on other skin sites.
INVESTIGATIONS
Skin biopsy shows parakeratosis, atypical keratinocytes with or without koilocytes.
There may be clusters of atypical keratinocytes invading the basement membrane to form small clusters in the papillary or reticular dermis.
Lichen planus
SIGNS / SYMPTOMS
Usually widely spread and pruritic rash.
INVESTIGATIONS
Skin biopsy shows features characteristic of each lichen planus.
Epidermal nevus
SIGNS / SYMPTOMS
Pruritic plaques
INVESTIGATIONS
Skin biopsy shows features characteristic of each epidermal nevus.
Melanocytic nevus
SIGNS / SYMPTOMS
Generally brown or tan in color.
There are no tiny black dots on the surface.
INVESTIGATIONS
Skin biopsy shows features characteristic of melanocytic nevus.
Melanoma
SIGNS / SYMPTOMS
Lesions often have an irregular outline, diameter greater than 6 mm, and color variegation.
INVESTIGATIONS
Skin biopsy shows features characteristic of melanoma.
Molluscum contagiosum
SIGNS / SYMPTOMS
Lesions appear as umbilicated, pearl-like, smooth papules.
At least one third develop symptoms of local erythema, swelling, or pruritus.
Seen particularly in immunocompromised patients.
INVESTIGATIONS
Hematoxylin and eosin staining shows Henderson Patterson bodies, the definitive histological feature of molluscum contagiosum.
Tuberculosis verrucosa cutis
SIGNS / SYMPTOMS
Wart-like papule with a subtle inflammatory rim at trauma-prone sites, such as the hands and digits, as well as the lower extremities in children. Lesions enlarge gradually, often in a serpiginous manner, to form a reddish-brown verrucous plaque. Central areas may become fluctuant with pus and keratinaceous debris. After several years, the plaques may heal spontaneously.[4]
INVESTIGATIONS
Histology shows acute inflammation in the epidermis, pseudoepitheliomatous hyperplasia, microabcesses in the upper dermis, sparse granulomatous foci, and occasional bacilli.[4]
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