An eccrine nevus is a rare, benign cutaneous hamartoma characterized by a localized proliferation of morphologically mature eccrine sweat glands. It is classified as a developmental abnormality rather than a true neoplasm, involving an increase in the number or size of eccrine secretory coils and ducts within the dermis.
Clinical Presentation
Eccrine nevi typically manifest as solitary, skin-colored or slightly erythematous plaques or nodules. They are most commonly observed on the trunk or extremities. While the lesions may be present at birth (congenital), they often become more apparent during childhood or adolescence.
The most characteristic clinical feature of an eccrine nevus is localized hyperhidrosis, or excessive sweating, confined to the area of the lesion. This sweating may occur spontaneously or can be triggered by emotional stress, thermal stimuli, or physical activity. In some cases, the lesion may be asymptomatic and lack associated hyperhidrosis.
Histopathology
Diagnosis is confirmed through histopathological examination of a skin biopsy. The primary finding is a significant increase in the density or size of mature eccrine units in the deep dermis or subcutaneous tissue. These glands are typically indistinguishable from normal eccrine glands in structure. Unlike the eccrine angiomatous nevus, a related but distinct entity, the eccrine nevus lacks a prominent vascular or capillary component.
Pathogenesis and Diagnosis
The exact etiology of eccrine nevi remains unknown, though they are considered a localized error in structural development. Differential diagnoses often include other sweat gland tumors, such as poromas or spiradenomas, as well as eccrine angiomatous nevi.
Clinical evaluation may involve a starch-iodine test (Minor’s test) to objectively map the area of hyperhidrosis. Because the lesions are benign, treatment is generally not medically required unless requested for cosmetic reasons or to manage symptomatic hyperhidrosis. In such cases, surgical excision or localized botulinum toxin injections may be considered.