Hobnail haemangioma
Targetoid haemosiderotic haemangioma; superficial haemosiderotic lymphovascular malformation; THH
Hobnail haemangioma is a benign vascular lesion that classically presents as a solitary red-brown to violaceous papule surrounded by a pale halo and an outer ecchymotic ring — the targetoid appearance that gave it its alternative name (targetoid haemosiderotic haemangioma). It is a frequent clinical mimic of melanoma and Kaposi sarcoma because of the dark central papule and surrounding pigment, and is often excised as a precaution. Histologically it shows characteristic "hobnail" endothelial cells with apical nuclei protruding into vessel lumina, accompanied by dermal haemosiderin deposition. Benign with no metastatic potential.
Clinical features
- Solitary red-brown to violaceous papule, 5–15 mm.
- Targetoid appearance — central dark papule + pale halo + outer ecchymotic ring (haemosiderin deposition).
- Common sites — trunk, extremities; rarely face.
- Median age 25–45; both sexes; often history of mild trauma to the area.
- Slow growth over months; ecchymotic features may fluctuate.
- Often clinically misdiagnosed as melanoma, Kaposi sarcoma, dermatofibroma or pyogenic granuloma — excisional biopsy is the rule.
Histology
- Biphasic vascular proliferation:
- Superficial dilated thin-walled vessels with characteristic "hobnail" endothelial cells — flattened cells with apical nuclei bulging into lumina like tacks.
- Deeper slit-like vessels in collagen.
- Dermal haemosiderin and erythrocyte extravasation responsible for the ecchymotic ring.
- Immunohistochemistry — CD31, ERG positive; D2-40 / podoplanin positive in some (suggesting lymphatic differentiation in part).
- Differential — Kaposi sarcoma (HHV-8 / LANA-1 positive), microvenular haemangioma, retiform haemangioendothelioma (more aggressive).
Management
- Excisional biopsy — diagnostic and definitive.
- Histology confirms benign nature; reassurance.
- Recurrence after complete excision uncommon.
- Multiple lesions or atypical features — consider retiform haemangioendothelioma (more aggressive); specialist review.
References
- Santa Cruz DJ, Aronberg J. Targetoid hemosiderotic hemangioma. J Am Acad Dermatol; 1988.
- Mentzel T et al. Hobnail hemangioma — clinicopathologic, immunohistochemical study. J Cutan Pathol; 1999.
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