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Neuroradiology Case of the Week

Case 374

January 2009

Trushar Sarang, MD

Clinical Presentation: Patient is a 52-year-old male presenting after a motor vehicle collision.

Imaging Findings: Multiple high attenuation subcutaneous nodules covering the scalp.

Diagnosis: Sebaceous cysts of the scalp

Discussion: Scalp masses have a wide differential. This patient presented with multiple, non-tender nodules as an incidental finding on a trauma CT series. The lesions are well defined, without signs of bony erosion or malignant spread. There is no stranding of the surrounding fat. A concise differential of benign appearing nodules would include sebaceous cysts, varicose veins, lipomas, fat necrosis, epidermal inclusion cysts, glomus tumor, and neurofibromas. Metastasis and lymphoma are rare considerations. Other, very rare considerations would include histiocytosis and various skin cancers (including Merkel cell, pilomatrixoma, melanoma and angiosarcoma). Traumatic causes would include subgaleal hematomas or foreign bodies.
     Given the homogeneous high density soft tissue composition of the nodules, the leading differential would include sebaceous cysts versus epidermal inclusion cysts. The former contains sebaceous glands on histology where as the inclusion cysts do not. The two are indistinguishable on CT. There is some controversy over the nomenclature regarding these skin lesions--some believe that sebaceous cysts and inclusion cysts to be the same entity.
     Interestingly, this patient has a diagnosis of basal cell nevi syndrome.  Both sebaceous cysts and epidermal inclusion cysts are seen in association with this condition.

References:

1. Ho VCY. Benign epithelial tumors. IN: Freedberg IM, Eisen AZ, Wolff K, et al, eds. Fitzpatrick's Dermatology in General Medicine. 5th ed. New York: McGraw-Hill;1999:884-5.
2. Leppard BJ. Skin cysts in the basal cell naevus syndrome. Clin Exp Dermatol. 1983 Nov;8(6):603-12. [PubMed]
3. Elder D, Elenitsas R, Johnson BL, Murphy GF, eds. Lever's Histopathology of the Skin. 8th Ed. Philadelphia, Lippincott-Raven. Chapter 30, 694-7, 1997.