Hidradenoma
Clear cell hidradenoma; nodular hidradenoma; solid-cystic hidradenoma; eccrine acrospiroma (older term)
Hidradenoma is a benign sweat-duct adnexal tumour that presents as a solitary, firm, dome-shaped, skin-coloured to pink-blue nodule, 5–30 mm, on the head, neck, trunk or extremities of an adult. Histologically it is a well-circumscribed dermal nodule of polygonal eosinophilic or clear cells, with frequent cystic spaces and duct formation. Its clinical importance lies in (1) being a common unexpected pathology call on a clinically banal nodule and (2) the existence of a rare malignant counterpart (hidradenocarcinoma) with metastatic potential.
Clinical features
- Solitary firm, dome-shaped or polypoid nodule, 5–30 mm.
- Skin-coloured to pink, sometimes with a bluish hue suggesting cystic component.
- Distribution — head and neck, trunk, proximal extremities; rarely genital.
- Slow growth over months to years; occasional ulceration or serous discharge.
- Median age 30–60; women slightly over-represented.
Histology
- Well-circumscribed dermal/subcutaneous nodule with solid and cystic areas.
- Two cell populations — polygonal eosinophilic / clear cells and smaller basaloid cells.
- Duct formation, hyalinised stroma, often cystic degeneration.
- Immunohistochemistry — CK7+, EMA+; clear-cell variant is glycogen-rich (PAS+, diastase-labile).
- CRTC1-MAML2 fusion is found in a subset of (clear-cell) hidradenomas.
- Differential — eccrine spiradenoma, cylindroma, hidradenocarcinoma (atypia, infiltrative growth, mitoses).
Management
- Complete surgical excision with histology.
- Recurrence after complete excision is uncommon; incomplete excision warrants re-excision.
- Atypical features or recurrence — review for hidradenocarcinoma; MDT discussion, baseline imaging.
References
- Hernandez-Perez E, Cestoni-Parducci R. Nodular hidradenoma — clinical and histologic review. J Am Acad Dermatol; 1985.
- Kazakov DV et al. Hidradenoma and related neoplasms — molecular and pathological review. Histopathology; 2010.
- WHO Classification of Tumours Editorial Board. Skin Tumours, WHO Classification of Tumours, 5th ed., vol. 12. Lyon: IARC; 2025.
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