Poroma : Article by Timothy Mccalmont, MD Page 1 of 8

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Author Information Rate this Article Introduction Poroma Clinical Email to a Colleague Differentials Last Updated: February 22, 2007 Workup Get CME/CE for article Treatment Synonyms and related keywords: poroma, apocrine poroma, juxtaepidermal poroma, juxta- Follow -up epidermal poroma, hidroacanthoma simplex, dermal duct tumor, adnexal neoplasm, adnexal tumor, Miscellaneous eccrine poroma, poromatosis, intraepidermal poroma, dermal poroma, poroid hidradenoma, Pictures acrospiroma Bibliography

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Author Information Introduction Clinical Differentials Workup Treatment Follow -up Miscellaneous Pictures Bibliography Related Articles Author: Timothy McCalmont, MD , Director, UCSF Dermatopathology Service, Seborrheic Professor of Clinical Pathology and Dermatology, Departments of Pathology and Keratosis

Dermatology, University of California at San Francisco Squamous Cell Timothy McCalmont, MD, is a member of the following medical societies: Alpha Carcinoma Omega Alpha , American Medical Association , American Society of Dermatopathology , California Medical Association , College of American Trichilemmoma Pathologists , and United States and Canadian Academy of Pathology Editor(s): Evan R Farmer, MD , Professor of Dermatology, Johns Hopkins University School of Medicine, Clinical Professor of Pathology, Virginia Continuing Commonwealth University School of Medicine; Consulting Staff, Department of Education Dermatology, Johns Hopkins Hospital, VCU Health Services; Richard P Vinson, CME available for MD , Assistant Clinical Professor, Department of Dermatology, Texas Tech this topic. Click University School of Medicine; Consulting Staff, Mountain View Dermatology, PA; here to take this CME. Jeffrey Meffert, MD , Assistant Clinical Professor of Dermatology, Medicine, University of Texas Health Science Center-San Antonio; Joel M Gelfand, MD, MSCE , Medical Director, Clinical Studies Unit, Assistant Professor, Department of Patient Education Dermatology, Associate Scholar, Center for Clinical Epidemiology and Click here Biostatistics, University of Pennsylvania; and Dirk M Elston, MD , Director, patient education. Department of Dermatology, Geisinger Medical Center

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INTRODUCTION Section 2 of 10

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Background: A poroma is a benign adnexal neoplasm composed of epithelial cells that show tubular (usually distal ductal) differentiation. The malignant counterpart of a poroma is referred to as porocarcinoma. Poromas historically have been considered glandular adnexal neoplasms of eccrine lineage, and this view is so entrenched that the neoplasm is often referred to as eccrine poroma; however, recent analyses by many investigators suggest that poromas can be of either eccrine or apocrine lineage. Apocrine poromas are probably more common than those of eccrine lineage.

Poromas belong to the spectrum of acrospiromas, along with nodular hidradenomas, clear cell hidradenomas, dermal duct tumors, and hidroacanthoma simplex.

Pathophysiology: A poroma is a benign neoplasm that shows differentiation toward poroid (glandular ductal) cells. The malignant counterpart of poromas is porocarcinoma, which also shows poroid differentiation. Poromas occur only in the skin and are not known to affect any other tissues.

Frequency:

In the US: Precise prevalence figures have not been calculated for this benign neoplasm.

Internationally: The worldwide prevalence is not thought to differ from that observed in the United States.

Mortality/Morbidity: A poroma usually manifests as a solitary papule or nodule. Most lesions are asymptomatic, but minor pain can accompany some lesions. Rarely, the patient develops multiple poromas simultaneously, a phenomenon known as poromatosis. Multiple poromas may be of cosmetic concern and are sometimes disabling, especially if involvement of the sole is noted.

Race: Poromas are not known to have racial or ethnic predilection.

Sex: No sex predilection is known in the distribution of poromas. Males and females are equally affected.

Age: Poromas can develop in persons of any age, but onset is typically in adulthood.

CLINICAL Section 3 of 10

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History:

Poromas typically are asymptomatic, slow-growing, or stable nodular lesions.

Although most are asymptomatic, pain can be a presenting sign.

Poromas are one of many types of benign adnexal neoplasms that can manifest secondarily within a nevus sebaceus.

Physical:

Poromas typically manifest as skin-colored papules or nodules smaller than 2 cm in diameter.

Poromas may occasionally manifest as pigmented lesions.

Protuberant lesions may exhibit surface erosion or ulceration.

Rarely, a poroma manifests in association with nevus sebaceus as a secondary neoplasm.

Causes: The specific causes of poromas are not known. In contrast to some adnexal neoplasms of follicular lineage, poroma development has no established familial predilection. DIFFERENTIALS Section 4 of 10

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Seborrheic Keratosis Squamous Cell Carcinoma Trichilemmoma

Other Problems to be Considered:

Hidradenoma Acrospiroma Poroid hidradenoma

WORKUP Section 5 of 10

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Lab 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

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appropriately trained and certified dermatopathologist.

Imaging Studies:

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

Other Tests:

No other testing is applicable.

Procedures:

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.

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.

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.

Staging: Staging is not applicable to the evaluation of a benign neoplasm. TREATMENT Section 6 of 10

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Medical Care: Poromas do not require medical care; rather, they are diagnosed and treated surgically.

Surgical Care: The diagnosis and treatment of poromas is typically performed via simple complete excision.

Consultations: Poromas are not clinically distinctive and usually cannot be diagnosed clinically; however, an experienced clinical dermatologist can sometimes recognize a poroma, especially one with a vascular appearance that develops on a volar surface.

Diet: Diet is irrelevant to the development or natural history of this neoplasm.

Activity: Poromas are unrelated to activity and do not contribute to any restriction in activity, with the possible exception of a painful lesion involving the sole of the foot. FOLLOW-UP Section 7 of 10

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Further Inpatient Care:

Inpatient care is not required.

Further Outpatient Care:

No additional care is required.

In/Out Patient Meds:

No medications are relevant or required.

Deterrence/Prevention:

No preventative measures for benign adnexal neoplasms are known at this time.

Complications:

No complications are specifically associated with poromas. The surgical treatment of poromas can produce the same common complications (eg, infection, hemorrhage) associated with any minor surgical procedure.

Prognosis:

The prognosis of poromas is favorable because the lesions have no known clinical significance. Even poromatosis (multiple poromas) is not known to be associated with other anomalies. The risk of malignant transformation of a poroma is minimal and is thought to be similar to that of normal skin.

MISCELLANEOUS Section 8 of 10

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Medical/Legal Pitfalls:

Misdiagnosis of a poroma as another form of adnexal neoplasm: The diagnosis of a poroma is a relatively nonlitigious area of medicine because such mischaracterization typically is of little consequence as long as the lesion is correctly recognized as benign.

Misdiagnosis of a benign poroma with extensive necrosis as squamous cell carcinoma: The risk for misdiagnosis is amplified in a partial sample because the circumscription of the lesion in question cannot be fully assessed. This may lead to unnecessary surgery on a lesion that has been misclassified.

PICTURES Section 9 of 10

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Caption: Picture 1. Poroma. Courtesy of Jeffrey Meffert, MD.

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Picture Type: Photo Caption: Picture 2. This vascular-appearing poroma presented on the tip of the toe.

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Picture Type: Photo Caption: Picture 3. This intradermal poroma (dermal duct tumor) shows a sharply circumscribed border at scanning magnification. Highly vascularized and focally sclerotic stroma is also evident.

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Picture Type: Photo Caption: Picture 4. At higher magnification, ductal differentiation is conspicuous.

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Picture Type: CT Caption: Picture 5. This juxtaepidermal poroma presents histopathologically in continuity with the epidermis, creating a seborrheic keratosis-like profile.

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eMedicine Zoom View (Interactive!) Picture Type: CT Caption: Picture 6. At higher magnification, this poroma is composed of monomorphous small keratinocytes with "cuboidal" cytomorphology.

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Picture Type: CT Caption: Picture 7. This poroma shows focal sebaceous differentiation, indicating that the lesion is of folliculosebaceous-apocrine (rather than eccrine) lineage.

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Picture Type: CT

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BIBLIOGRAPHY Section 10 of 10

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Altamura D, Piccolo D, Lozzi GP, Peris K: Eccrine poroma in an unusual site: a clinical and dermoscopic simulator of amelanotic melanoma. J Am Acad Dermatol 2005 Sep; 53(3): 539 [Medline] . Barankin B, Shum D, Guenther L: Tumors arising in nevus sebaceus: a study of 596 cases. J Am Acad Dermatol 2001 Nov; 45(5): 792-3; author reply 794[Medline] . Goldner R: Eccrine poromatosis. Arch Dermatol 1970 May; 101(5): 606-8[Medline] . Harvell JD, Kerschmann RL, LeBoit PE: Eccrine or apocrine poroma? Six poromas with divergent adnexal differentiation. Am J Dermatopathol 1996 Feb; 18(1): 1-9[Medline] . Hashimoto K, Lever WF: Skin appendage tumors. Arch Dermatol 1970 Feb; 101(2): 252 - [Medline] . Jaqueti G, Requena L, Sanchez Yus E: Trichoblastoma is the most common neoplasm developed in nevus sebaceus of Jadassohn: a clinicopathologic study of a series of 155 cases. Am J Dermatopathol 2000 Apr; 22(2): 108-18 [Medline] . Kakinuma H, Miyamoto R, Iwasawa U, et al: Three subtypes of poroid neoplasia in a single lesion: eccrine poroma, hidroacanthoma simplex, and dermal duct tumor. Histologic, histochemical, and ultrastructural findings. Am J Dermatopathol 1994 Feb; 16(1): 66-72 [Medline] . McCalmont TH: A call for logic in the classification of adnexal neoplasms. Am J Dermatopathol 1996 Apr; 18(2): 103-9[Medline] .

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