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May 2010

Irregular Erythematous Nodule on the Upper Arm—Diagnosis

Author Affiliations


Arch Dermatol. 2010;146(5):557-562. doi:10.1001/archdermatol.2010.77-b

Histologic analysis revealed an intradermal nodule that was composed predominantly of monomorphic poroid cells with uniform round or oval nuclei and scant cytoplasm as well as cuticular cells that were larger and more pale staining, with abundant eosinophilic cytoplasm. Ductlike structures were present, and there was no connection between the tumor and the overlying epidermis. Large, sharply circumscribed foci of necrosis were evident within the tumor nodule.

Poromas are benign neoplasms of eccrine differentiation. Hidradenomas, which are derived from either apocrine or eccrine glands, have been known by various names (solid-cystic hidradenoma, eccrine acrospiroma, clear-cell hidradenoma, and poroid hidradenoma) depending on slight morphological variations. Poroid hidradenoma is one of the less commonly reported variants. Clinically, PHs almost always occur as solitary lesions.1 They are usually asymptomatic but can sometimes be tender,2-4 particularly when the lesion is papular and located in an area where it can easily catch on clothing and become irritated, as in the present case. There is no sex predilection, and the lesion can occur in almost any location on the skin, with the most commonly reported sites being the scalp, face, trunk, and extremities.1-8 Most tumors are slow growing, and complete simple excision is usually curative. Our patient is typical in that she had no recurrence during 2 years of follow-up after the excision.

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