Tricholemmal Carcinoma
David Cassarino, MD, PhD
Key Facts
Terminology
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Tricholemmal carcinoma (TLC)
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Low-grade malignant tumor of clear-staining squamous cells with tricholemmal differentiation
Clinical Issues
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Occurs in sun-damaged skin of the elderly
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Excellent, local recurrence potential but no confirmed metastatic cases
Microscopic Pathology
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Lobulated to nodular, predominantly dermal-based tumor
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Typically composed of a proliferation of large clear cells with cytologic atypia
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Areas of tricholemmal (pilar)-type keratinization without intervening granular layer
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Peripheral palisading and thickened basement membrane often seen
TLC is a clear cell neoplasm that may show multiple attachments to the epidermis and overlying ulceration and crusting  . Inset shows atypical cells with prominent nucleoli and multiple mitotic figures  . |
High magnification of another case of TLC shows a proliferation of pale to clear cells with cytologic atypia, mitotic figures  , and a focally thickened basement membrane  . |
TERMINOLOGY
Abbreviations
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Tricholemmal carcinoma (TLC)
Synonyms
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Trichilemmal carcinoma
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Malignant tricholemmoma
Definitions
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Low-grade malignant tumor of clear-staining squamous cells with tricholemmal/outer root sheath differentiation
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Has been classified as a low malignant potential variant of squamous cell carcinoma (SCC)
ETIOLOGY/PATHOGENESIS
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