Poroma Workup

Updated: Nov 07, 2019
  • Author: Timothy McCalmont, MD; Chief Editor: Dirk M Elston, MD  more...
  • Print

Laboratory Studies

Blood laboratory testing is not necessary for the diagnosis of a poroma and is not appropriate in the evaluation of an afflicted patient. The diagnosis typically cannot be made based solely on clinical findings alone, although an experienced observer may recognize the entity. The diagnosis can be fully established after surgical excision with subsequent microscopical examination by an appropriately trained and certified dermatopathologist.


Imaging Studies

Imaging studies are not needed in the evaluation of this benign and typically superficial adnexal neoplasm.

In a dermoscopy evaluation, Altamura et al suggested poroma can mimic amelanotic melanoma. [17, 18]


Other Tests

No other testing is applicable.



No procedures (other than simple excision) are applicable to this entity.


Histologic Findings

Like all benign neoplasms, poromas typically show relatively sharp circumscription. Most tend to be small, although sizable tumors can be encountered. Poromas are composed of small cuboidal epithelial cells with monomorphous ovoid nuclei and inconspicuous nucleoli. The individual neoplastic cells have compact eosinophilic cytoplasm. Areas of ductal differentiation are manifested as tubules lined by a dense eosinophilic cuticle, and, sometimes, cytoplasmic vacuoles can also be seen as an indicator of luminal differentiation. Although poromas can usually be deemed benign based on circumscription and benign cytologic features, these lesions not uncommonly show small foci of necrosis en masse and a highly vascularized (granulation tissue–like) stroma, the combination of which can create concern for malignancy, especially in inexperienced observers.

Poromas manifest several different variations.

Intraepidermal poroma (historically known as hidroacanthoma simplex) represents a form of poroma in which nests of cells with tubular differentiation are confined to the surface epidermis, with no evidence of dermal involvement. This pattern of poromas can sometimes cause confusion with other entities that may exhibit an intraepidermal pattern of growth, including seborrheic keratosis and melanocytic neoplasms. See the images below.

This intradermal poroma (dermal duct tumor) shows This intradermal poroma (dermal duct tumor) shows a sharply circumscribed border at scanning magnification. Highly vascularized and focally sclerotic stroma is also evident.
At higher magnification, ductal differentiation is At higher magnification, ductal differentiation is conspicuous.

Juxtaepidermal poroma refers to a pattern of poroma in which nests and thick cords of cells are in continuity with the epidermis but also involve the superficial dermis. The intervening stroma is highly vascularized, as described above. See the images below.

This juxtaepidermal poroma presents histopathologi This juxtaepidermal poroma presents histopathologically in continuity with the epidermis, creating a seborrheic keratosis-like profile.
At higher magnification, this poroma is composed o At higher magnification, this poroma is composed of monomorphous small keratinocytes with "cuboidal" cytomorphology.

Dermal poroma (historically referred to as dermal duct tumor) represents a pattern of poroma confined wholly to the dermis. Some intradermal poromas have relatively little stroma, while others display the highly vascularized stroma that is typical of superficial poromas.

Poromas belong to the family of tumors known as acrospiromas. These tumors all differentiate towards the acrosyringium. Other variants of acrospiroma include clear cell hidradenoma and nodular hidradenoma. Mixed patterns are common. See the image below.

This poroma shows focal sebaceous differentiation, This poroma shows focal sebaceous differentiation, indicating that the lesion is of folliculosebaceous-apocrine (rather than eccrine) lineage.


Staging is not applicable to the evaluation of a benign neoplasm.