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WHO Classification of Tumours
Cystic sebaceous tumour


Cystic sebaceous tumour (CST) is a large adnexal neoplasm almost always associated with Muir-Torre syndrome (MTS)
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Rütten A, Burgdorf W, Hügel H, Kutzner H, Hosseiny-Malayeri HR, Friedl W, Propping P, Kruse R (1999)
Cystic sebaceous tumors as marker lesions for the Muir-Torre syndrome: a histopathologic and molecular genetic study.
Am J Dermatopathol 21: 405-13

. It most commonly arises on the upper trunk and typically presents as a solitary, well-circumscribed dermal nodule resembling a hair follicle cyst. The tumour usually extends into the subcutis and may be connected to the upper dermis. A well-differentiated CST shows a cystic growth pattern and is composed of fully differentiated vacuolated sebocytes bordered by a narrow rim of undifferentiated basaloid sebacous matrix cells. The cyst wall may contain ductal structures. There is no cytological atypia and only few mitoses. More solid CST variants are made up predominantly of undifferentiated sebaceous cells with variable cytologic atypia and mitoses.
Cystic sebaceous tumours typically arise in adults >40 years of age and show a predilection for males. CST is a diagnostic marker for the hereditary Muir-Torre syndrome, which is caused by genetic alterations within the DNA mismatch repair genes. Most MTS patients are affected with a variety of internal malignancies. The prognosis depends on the nature of these internal malignancies

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LeBoit PE, Burg G, Weedon D, Sarasin A (Eds.)
World Health Organization Classification of Tumours. Pathology and Genetics of Skin Tumours
3rd Edition
IARC Press: Lyon 2005