Tricholemmal Carcinoma
David Cassarino, MD, PhD
Key Facts
Terminology
Tricholemmal carcinoma (TLC)
Low-grade malignant tumor of clear-staining squamous cells with tricholemmal differentiation
Clinical Issues
Occurs in sun-damaged skin of the elderly
Excellent, local recurrence potential but no confirmed metastatic cases
Microscopic Pathology
Lobulated to nodular, predominantly dermal-based tumor
Typically composed of a proliferation of large clear cells with cytologic atypia
Areas of tricholemmal (pilar)-type keratinization without intervening granular layer
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
Tricholemmal carcinoma (TLC)
Synonyms
Trichilemmal carcinoma
Malignant tricholemmoma
Definitions
Low-grade malignant tumor of clear-staining squamous cells with tricholemmal/outer root sheath differentiation
Has been classified as a low malignant potential variant of squamous cell carcinoma (SCC)
ETIOLOGY/PATHOGENESIS
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