Poroid hidradenoma of the scalp in an immunosuppressed patient

Abstract

We discuss the rare finding of what initially presented as a common subcutaneous scalp nodule. Yet, after surgical excision, the lesion was found to be a poroid hidradenoma (PH). PH is a rare variant of poroid neoplasms. PH, when observed, is commonly associated with the head and neck. However, it is rarely described in literature beyond the dermatopathologic findings. Here, we describe the clinical presentation of a unique case of a scalp PH in the setting of immunosuppression.

Poroid hidradenoma of the scalp

“…In 1990, Abenoza and Ackerman [ 1 ] described four poroid neoplasm variants according to neoplastic cell location: poroid hidradenoma, eccrine poroma, dermal duct tumor, and hidroacanthoma simplex. As these tumors derive from eccrine glands, variants are located entirely within the dermis [ 3 ]. Poroid hidradenoma is a tumor with solid and cystic components, where neoplastic poroid cells are all located within the dermis and without connection to the epidermis [ 4 ].…”

Poroid hidradenoma of the scalp in a US Veteran’s Administration (VA) patient

“…A systematic review found that the preferred treatment is surgical excision; however, it is unknown whether other treatment options would work as they have not been explored [ 8 ]. Although one study suggested ultrasound may be useful in diagnosis—as these lesions have solid and cystic components vs. other entities like lipomas, which are homogenous—most lesions were excised without any pre-operative imaging or another workup other than clinical exam [ 3 , 4 , 6 , 7 ]. Due to the lack of information, there are no consensus guidelines or recommended surveillance regimens either.…”

“…The tumor is reported to be well-circumscribed [ 7 ]. Poroid hidradenomas have been reported in the scalp, neck, arm, hand, thigh, back, and vulva [ 4 , 6–12 ]. This patient presented with the typical poroid cells usually found on histology for such lesions and his mass was within the typical size range.…”

“…Some studies suggest that these lesions are more common in immunosuppressed patients, such as liver transplant recipients and hematopoietic stem cell transplant recipients [ 4 , 16 ]. There are also case reports of lesions having features of both eccrine poromas and poroid hidradenomas [ 10 , 11 ].…”

“…One histopathological series found only four poroid hidradenomas out of 18,653 biopsy specimens [ 3 ]. The largest case series reported fifty-six poroid hidradenomas but again, these specimens were mainly distinguished on a histologic basis [ 4 ]. These tumors arise from eccrine cells and are contained entirely in the dermis [ 5 ].…”