Tricholemmoma



Tricholemmoma


David Cassarino, MD, PhD










Scanning magnification of a small tricholemmoma shows a symmetric, well-circumscribed, lobular neoplasm with epidermal attachments image. Centrally, the lesion shows desmoplastic TL features image.






High magnification of a TL shows bland-appearing small cells with pale to clear-staining cytoplasm and small nucleoli. There is a thickened peripheral basement membrane image.


TERMINOLOGY


Abbreviations



  • Tricholemmoma (TL)


  • Desmoplastic tricholemmoma (dTL)


Synonyms



  • Trichilemmoma


Definitions



  • Benign clear cell adnexal proliferation with external root sheath differentiation


ETIOLOGY/PATHOGENESIS


Unknown in Most Cases



  • Some have considered TL to be related to HPV infection (“tricholemmal verrucae”)



    • Not generally accepted, and most PCR studies for HPV have been negative


Genetic



  • Some cases are associated with Cowden syndrome (PTEN hamartoma syndrome)



    • Characterized by multiple tricholemmomas, hamartomas, and visceral tumors including breast and thyroid carcinomas


    • Mutation of PTEN, a tumor suppressor gene, on 10q23.31


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Relatively common tumors


  • Age



    • Usually adults, although Cowden syndrome patients present earlier


Site



  • Most occur on face, especially nose and upper lip


Presentation



  • Small papular lesion



    • Usually flesh-colored


    • Often clinically mimics basal cell carcinoma or verruca


Treatment



  • Surgical approaches



    • Usually not necessary, as these are benign tumors


    • Complete conservative excision is curative


Prognosis



  • Excellent, no malignant potential


  • Cowden syndrome patients have high risk of internal malignancies


MICROSCOPIC PATHOLOGY


Histologic Features

Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Tricholemmoma
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