A periungual eccrine poroma masquerading as amelanotic melanoma: a case report.

Background: Eccrine poroma (EP) is a benign cutaneous neoplasm that originates from the acrosyringium of the eccrine sweat duct. EP can be found on any skin area with sweat glands and typically occurs on the palmoplantar areas. They usually present as solitary, asymptomatic, well-circumscribed, smooth or verrucous papules or nodules that range in color from skin-colored to red or brown. However, some cases may be difficult to diagnose clinically, especially when the distribution and morphology are not typical. The periungual region represents an uncommon localization for these neoplasms and can easily be misdiagnosed.

Case description: Here, we present a rare case of a 52-year-old man who presented with a 2-year history of a painless, slowly growing, erythematous nodule on the lateral nail fold of his right toe. The lesion was initially suspected to be an amelanotic melanoma, but histopathological revealed a tumor composed of broad anastomosing bands of cuboidal cells with eosinophilic cytoplasm and round nuclei within the dermis, confirmed to be an EP. After complete surgical excision of the lesion with 1 mm margins, the wound healed well and there was no recurrence or metastasis after 12 months of follow-up.

Conclusions: EPs in the periungual region are exceedingly rare. Their presentation and atypical appearance can lead to misdiagnosis and missed opportunities for early treatment. Clinicians should be aware of this possibility and perform biopsies of any suspicious periungual lesion to ensure timely and appropriate management.