Sebaceoma
Sebaceous epithelioma (older term); cystic sebaceous neoplasm (cystic variant)
Sebaceoma is a benign sebaceous neoplasm that sits histologically between sebaceous adenoma (≥ 50% mature sebocytes) and sebaceous carcinoma (atypical infiltrative tumour). It is composed of an admixture of basaloid germinative cells and mature sebocytes, with the basaloid (germinative) component predominating over scattered mature sebocytes (a descriptive continuum rather than a formally defined cut-off). Like sebaceous adenoma, sebaceoma is a recognised Muir-Torre syndrome marker — particularly when multiple or arising at extrafacial sites — and mandates mismatch-repair immunohistochemistry. Complete surgical excision is curative; the differential diagnosis from BCC can be subtle clinically.
Clinical features
- Solitary firm yellow-pink to red-orange papule or nodule, 5–20 mm.
- Distribution — face (scalp, forehead, eyelid), occasionally trunk and limbs.
- Slow growth; central depression or umbilication may be present.
- Age typically 50–70; both sexes.
Histology
- Well-circumscribed dermal neoplasm with mixed basaloid germinative cells and scattered mature sebocytes; basaloid component > 50%.
- No infiltrative growth, no significant atypia, mitoses few.
- Adipophilin and EMA confirm sebocytic differentiation.
- Cystic sebaceous tumour (cystic sebaceoma) — a highly Muir-Torre-suggestive variant.
- Differential — sebaceous adenoma (more mature sebocytes), sebaceous carcinoma (atypia, mitoses, infiltrative), trichoblastoma, basaloid follicular hamartoma.
Muir-Torre / Lynch screening
- Sebaceoma is a Muir-Torre marker; mismatch-repair IHC and Lynch evaluation as for sebaceous adenoma — see sebaceous adenoma and Muir-Torre syndrome.
- The cystic sebaceous tumour variant has a particularly high yield for MMR deficiency.
Management
- Complete surgical excision with histology.
- MMR-IHC on every sebaceous neoplasm; refer to genetics if MMR loss demonstrated.
- Reassurance after complete excision for solitary MMR-intact lesions.
References
- Troy JL, Ackerman AB. Sebaceoma — a distinctive benign neoplasm of adnexal epithelium differentiating toward sebaceous cells. Am J Dermatopathol; 1984.
- Misago N, Mihara I, Ansai S, Narisawa Y. Sebaceoma and related neoplasms with sebaceous differentiation. Am J Dermatopathol; 2002.
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