🔍 Search
Benign adnexalHair-follicleICD-10 D23.x

Trichoblastoma

TB · trichoblastic naevus · giant trichoblastoma

Trichoblastoma is a benign hair-follicle (follicular germ) tumour. It is the commonest secondary tumour to arise within a naevus sebaceus during adulthood and is also seen as a sporadic lesion or as part of Brooke-Spiegler syndrome (CYLD mutation). Its principal clinical importance is its histological resemblance to basal cell carcinoma (BCC), and its position within the spectrum of follicular germ-cell tumours that includes trichoblastic carcinoma. Most lesions are managed by simple excision.

CurrentLast reviewed 16 May 2026

Classification

  • Conventional trichoblastoma: nodular, often solitary.
  • Cribriform trichoblastoma: cribriform architecture.
  • Racemiform trichoblastoma: cord-like proliferation.
  • Adamantinoid trichoblastoma: peripheral palisading, central reticulation.
  • Giant trichoblastoma: >1 cm; trunk; younger patients.
  • Pigmented trichoblastoma: melanin pigment; melanoma DDx.
  • Within naevus sebaceus: most common secondary tumour in adult life.
  • Brooke-Spiegler syndrome: multiple trichoblastomas + cylindromas + spiradenomas; CYLD gene.

Clinical features

  • Slow-growing nodule or papule.
  • Sites: face, scalp, neck, trunk.
  • 0.5-3 cm; firm; sometimes pigmented (clinical mimic of BCC).
  • Asymptomatic; cosmetic / diagnostic concern.
  • Within naevus sebaceus: discrete nodule arising in long-standing yellow-orange plaque.
  • Brooke-Spiegler: multiple progressive scalp / face / trunk papules with family history.

Pathology

  • Basaloid cell aggregates with peripheral palisading and follicular germinative features.
  • Mesenchymal stroma intimately associated with epithelium (cf BCC where stroma retracts).
  • Few mitoses; no atypia; no perineural / lymphovascular invasion.
  • Connection to overlying epidermis is rare (cf BCC where common).
  • IHC:
    • BerEP4 positive (both BCC and trichoblastoma — limited discriminator).
    • PHLDA1 positive (trichoblastoma).
    • CK20 highlights Merkel cells (preserved in trichoblastoma, lost in BCC).
    • Stromal CD10 positive in trichoblastoma; reversed in BCC.
    • Androgen receptor more strongly positive in BCC.

Differentials

  • Basal cell carcinoma (BCC) — most important DDx; histology + IHC.
  • Trichoblastic carcinoma — malignant counterpart; atypia, mitoses, infiltrative growth.
  • Trichoepithelioma — closely related; smaller; multiple in Brooke-Spiegler.
  • Cylindroma / spiradenoma — Brooke-Spiegler overlap.
  • Pigmented BCC.
  • Fibroepithelioma of Pinkus.
  • Sebaceous adenoma.

Management

  • Excisional biopsy: complete local excision is curative.
  • Margins: simple narrow excision adequate; recurrence rare with complete excision.
  • If pathology suggests trichoblastic carcinoma: wider excision / Mohs / MDT discussion.
  • Brooke-Spiegler:
    • Clinical genetics referral; CYLD germline testing.
    • Annual dermatology surveillance (multiple lesions develop over decades).
    • Surgical removal of symptomatic / cosmetically prominent lesions.
    • Salicylates / aspirin emerging as potential CYLD-pathway modulator (off-label, trials).
  • Counsel about benign nature.

References

  1. Ackerman AB, de Viragh PA, Chongchitnant N. Neoplasms with follicular differentiation. Lea & Febiger; 1993.
  2. Sellheyer K. Basal cell carcinoma: cell of origin, cancer stem cell hypothesis, and stem cell markers. Br J Dermatol. 2011;164:696-711.
  3. Bowen S et al. Mutations in the CYLD gene in Brooke-Spiegler syndrome, familial cylindromatosis, and multiple familial trichoepithelioma. Am J Hum Genet. 2005;76:1073-1083.
  4. Cribier B et al. Tumors arising in nevus sebaceus: a study of 596 cases. J Am Acad Dermatol. 2000;42:263-268.

Spot a correction?

If any clinical statement, citation or link on this page needs updating, please email admin@skinoncology.net with the page name, the proposed correction and the supporting source.