Hidradenocarcinoma
Malignant nodular hidradenoma; clear-cell hidradenocarcinoma
Hidradenocarcinoma is a rare, aggressive sweat-gland (eccrine or apocrine) carcinoma representing the malignant counterpart of the benign hidradenoma. It usually presents as a slowly enlarging dermal/subcutaneous nodule on the head, trunk or extremities of older adults, but with a historical wide-excision series quote local recurrence ~30–50%; modern series with clear margins or Mohs report 10–20%. Combined nodal and distant metastatic rates of ~30–40% in older series correspond to ~20% nodal + ~10–15% distant in modern reports. Wide local excision is the cornerstone of management; sentinel-lymph-node biopsy and adjuvant radiotherapy/chemotherapy are increasingly used for high-risk disease. Emerging molecular targets include EGFR, HER2 and androgen receptor.
Clinical features
- Solitary, firm, slow-growing dermal/subcutaneous nodule.
- Most common on the head and neck (~half), then trunk, extremities.
- May ulcerate, bleed, or fix to deeper structures.
- Median age 60; M:F roughly equal.
- Often misdiagnosed clinically as cyst, lipoma or BCC.
Histology
- Multinodular dermal proliferation of polygonal, clear and squamoid cells.
- Cytological atypia, increased mitoses (atypical mitoses), tumour necrosis distinguishing from benign hidradenoma.
- Infiltrative borders; lymphovascular invasion in higher-risk lesions.
- Eccrine ductal differentiation (EMA, CEA highlight ducts); androgen receptor positive in some cases.
- HER2 over-expression has been reported in case reports; the proportion with true gene amplification on ISH is lower and HER2-targeted therapy in hidradenocarcinoma rests on anecdotal evidence — emerging therapeutic relevance.
Management
- Wide local excision with 1–2 cm margins; Mohs micrographic surgery for facial / functionally critical sites.
- Imaging staging (CT or PET-CT) for tumours >2 cm or high-grade histology.
- Sentinel lymph node biopsy considered for high-risk lesions.
- Adjuvant radiotherapy for positive margins, multiple positive nodes, perineural or lymphovascular invasion.
- Systemic therapy for metastatic disease — platinum-based chemotherapy, anti-HER2 therapy in HER2-amplified cases (off-licence), case reports of immune checkpoint inhibitor activity.
Prognosis
Local recurrence 30–50%; regional or distant metastasis up to 40%. 5-year overall survival 30–80% depending on stage at presentation, completeness of resection and histological grade. Aggressive surveillance over a 10-year period is appropriate.
References
- Gauerke S, Driscoll JJ. Hidradenocarcinomas — a review. Arch Pathol Lab Med; 2010.
- Soni A et al. HER2 amplification in hidradenocarcinoma — therapeutic implications. Mod Pathol; 2018.
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