Clinical Photograph of Poroma Clinical photograph shows a traumatized poroma on the lower back of an adult male, which presented as an irritated polypoid lesion.
Poroma With Squamoid Features Low magnification of a poroma with squamoid features shows a basaloid to squamoid-appearing neoplasm with multiple anastomosing connections between thickened cords of tumor cells and to epidermis. Note the ectatic ductal space on the left .
Poroma With Clear Cell Features Scanning magnification of a poroma with clear cell features shows a basaloid to clear cell neoplasm with multiple anastomosing connections between thickened cords of tumor cells and to epidermis .
Higher Magnification of Clear Cell Poroma Higher magnification of a clear cell area of poroma shows a proliferation of small cells with abundant pale to clear-staining cytoplasm and small nuclei lacking atypia.
TERMINOLOGY
Synonyms
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Hidroacanthoma simplex (intraepidermal poroma, syringoacanthoma)
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Acrospiroma (older term, includes both poroma and hidradenoma)
Definitions
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Benign adnexal proliferation with anastomosing cords of tumor cells exhibiting ductal differentiation
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Typically has multiple epidermal attachments, except for dermal duct tumor
ETIOLOGY/PATHOGENESIS
Unknown
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Rare cases associated with radiation therapy and pregnancy
May rarely be multiple (“poromatosis”)
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Formerly considered eccrine, but most cases likely of apocrine differentiation
May see sebaceous &/or follicular differentiation in apocrine cases
CLINICAL ISSUES
Epidemiology
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Incidence
Relatively common tumors
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Age
Usually occur in middle-aged adults
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Sex
Equal incidence in males and females
Site
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Most common on extremities, especially palmar and plantar surfaces
May also occur on trunk, head and neck
Presentation
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Solitary pink to reddish papular or nodular lesion
Minority of cases are pigmented
Some cases may be very vascular and bleed easily
Natural History
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Stable lesions; do not usually regress
Treatment
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Surgical approaches
Complete conservative excision is curative
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Typically recommended to prevent recurrence and rare transformation to porocarcinoma
Prognosis
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Excellent; most cases do not show aggressive behavior
MACROSCOPIC
General Features
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Superficial, firm papule or nodule
Size
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Generally < 1 cm but may be larger
MICROSCOPIC
Histologic Features
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Symmetric, well-circumscribed tumor with multiple epidermal attachments
Intraepidermal component is typically sharply demarcated from adjacent normal epidermis
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Broad, anastomosing columns and thickened cords of tumor cells