Eccrine poroma
Poroma; "Pinkus tumour" (older eponym); hidroacanthoma simplex (intraepidermal variant); poroid hidradenoma (deeper variant)
Eccrine poroma is a common benign sweat-duct adnexal tumour, first described by Pinkus in 1956, that classically presents as a slow-growing, well-circumscribed, soft, red-violaceous to skin-coloured papule or plaque on the sole or palm of a middle-aged adult. Its red-violaceous colour and tendency to bleed when traumatised closely mimic pyogenic granuloma and amelanotic melanoma, making it an important clinical differential. Variants include hidroacanthoma simplex (entirely intraepidermal), poroid hidradenoma (deep dermal) and dermal duct tumour (deep). The malignant counterpart — eccrine porocarcinoma — has substantial regional and distant metastatic potential and may arise within long-standing poromas.
Clinical features
- Solitary, slow-growing, well-circumscribed, soft, often pedunculated red-violaceous to skin-coloured papule or plaque, usually 1–2 cm.
- Distribution — soles (~50%), palms (~25%), trunk, head and neck.
- Median age 40–60; both sexes.
- Often present for years; may bleed with minor trauma; can be tender.
- "Cup-shaped" depression of the surrounding epidermis is a classical clinical clue.
- Differential: pyogenic granuloma, amelanotic melanoma, BCC, viral wart, fibroma, cherry haemangioma.
Dermoscopy
- Polymorphous vascular pattern — glomerular and irregular vessels.
- White-pink homogeneous areas alternating with white interlacing lines.
- "Yellow ring" or "leaf and flower" pattern in some cases.
- Caveat — overlap with amelanotic melanoma and porocarcinoma, particularly when atypical features present (asymmetry, ulceration, marked vascular polymorphism, peripheral pigmentation). Excisional biopsy with full histology is recommended for any clinically uncertain plantar / palmar nodule.
Histology & variants
- Sharp downgrowth of broad strands of small uniform poroid cells (small basaloid cells with monomorphous round nuclei) from the epidermis into the dermis, with foci of cuticular cells (larger eosinophilic cells lining duct lumina).
- Eccrine ductal differentiation — characteristic intracytoplasmic and stromal ducts (EMA-positive).
- "Cup-shaped" architecture with abrupt transition from poroid tumour to surrounding epidermis.
- No atypia, mitoses or necrosis in benign poroma.
- Variants:
- Hidroacanthoma simplex — entirely intraepidermal (no dermal component).
- Poroid hidradenoma — deep dermal nodular variant.
- Dermal duct tumour — deep dermal aggregate of small ducts.
- Differential by histology: porocarcinoma (atypia, mitoses, infiltrative growth, necrosis, high mitotic count); BCC (lacks ductal differentiation); seborrhoeic keratosis (no ductal differentiation, no poroid cells).
Management
- Surgical excision with narrow (3–5 mm) margins is curative; histology mandatory to exclude porocarcinoma.
- For solitary atypical-appearing lesion or any features suggestive of porocarcinoma — refer to skin cancer MDT and manage as porocarcinoma.
- Recurrence after complete excision <5%.
- Counsel about risk of malignant transformation in any new growth, ulceration, bleeding or change.
References
- Pinkus H et al. Eccrine poroma — tumours exhibiting features of the epidermal sweat duct unit. AMA Arch Derm; 1956.
- Sgouros D et al. Dermoscopy of eccrine poroma — review of clinical and dermoscopic features. J Eur Acad Dermatol Venereol; 2013.
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