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These lesions are usually isolated and rarely multiple. Although precisely identifying the primary lesion is essential in establishing a differential diagnosis, it is important to note that there is significant overlapping between a papule, a plaque, and a nodule. Indeed, a single disorder can manifest simultaneously or successively as each of these lesions, either through their growth or confluence, or by nature. Since it is vital to diagnose melanoma and other pigmented cancers, a biopsy is indicated in case of the slightest doubt. This situation also requires that clinical examination sometimes be completed by a careful inspection using a magnifier lens or a dermatoscope. The latter may provide additional elements that can help avoid biopsy in some instances. However, histopathological examination remains the “gold standard” for establishing the precise diagnosis of any skin tumor. Certain lesions may have a purple coloration and thus reflect a dermal inflammation (e.g., lichen planus) or an angiomatous proliferation (e.g., Kaposi’s disease). Certain violaceous palpable lesions are angiokeratomas. When they are numerous and distributed over the “underwear” area, they can reflect an overload disease such as Fabry disease, which, if diagnosed early, can be treated by enzyme replacement therapy. Serious renal, cardiac, and/or cerebral complications can thus be avoided.

FormalPara Box 32.1

Main Causes of Brown, Black, Blue, or Gray Palpable Lesions

Acanthosis nigricans

Acroangiodermatitis (pseudo-Kaposi’s sarcoma, ­arteriovenous fistula)

Acrochordon or skin tag

Angiokeratoma (usually violaceous)

Angiolymphoid hyperplasia with eosinophilia and Kimura disease

Angiosarcoma

Black piedra

Blue nevus

Botryomycoma

Bowenoid papulosis

Cutaneous B-cell lymphoma

Dermatofibrosarcoma

Dermatosis papulosis nigra (Castellani’s disease)

Glomus tumor (and glomangiomatosis)

Hemangioma (cavernous and verrucous)

Hidrocystoma

Kaposi’s disease

Leukemias (particularly acute myeloid leukemia 4 and 5, NK-lymphoma, and dendritic plasmacytoid CD56-positive lymphomas)

Melanocytic tumors (melanoma, nevus, etc.)

Metastases (particularly of melanoma)

Open comedo and dilated pore of Winer

Pigmented viral wart

Purple papules in lichen planus, granuloma annulare, and collagen vascular diseases

Seborrheic keratosis

Skin cancers and precancerous lesions (pigmented basal cell carcinoma, pigmented Bowen’s disease, pigmented actinic keratosis, pigmented eccrine porocarcinoma, etc.)

Urticaria pigmentosa

FormalPara Do Not Miss

Isolated lesions: melanoma and other pigmented cancers.

Multiple lesions (rare): metastases, namely, of ­melanoma, and leukemia cutis, as well as urticaria ­pigmentosa in cutaneous and systemic mastocytoses (usually macular), can have a brown coloration.

FormalPara Common

Nevus, fibroma, and acrochordon.