Nevus Sebaceus and Follicular Hamartomas



Nevus Sebaceus and Follicular Hamartomas


Steven D. Billings, MD





Key Facts


Clinical Issues



  • Nevus sebaceus



    • Usually presents on scalp in infancy, often at birth


    • Presents as yellowish flat to warty plaque


    • Often enlarges during puberty


  • Basaloid follicular hamartoma



    • Usually presents in adults


Microscopic Pathology



  • Nevus sebaceus



    • Abnormalities of epidermis, follicles, and sebaceous glands: Follicles are disorganized with primitive germs; sebaceous hyperplasia


    • Abnormalities of apocrine glands


    • Associated tumors arising within nevus sebaceus: Trichoblastoma (most common), syringocystadenoma papilliferum, BCC (rare)


  • Basaloid follicular hamartoma



    • Multifocal islands of basaloid epithelium: No retraction artifact; mitotic activity absent to rare


Top Differential Diagnoses



  • DDx of nevus sebaceus



    • Epidermal nevus: Lacks abnormalities of follicles and sweat glands


    • Sebaceous adenoma: Lacks epidermal acanthosis and follicular structures


    • Sebaceous hyperplasia: Mature follicles


  • DDx of basaloid follicular hamartoma



    • BCC: More cytologic atypia and mitotic activity, retraction spaces, inflammatory stroma







Nevus sebaceus has an acanthotic epidermis, often with a papillomatous surface image. The follicles have a disorganized appearance image, and there are often associated large sebaceous glands image.






Basaloid follicular hamartoma is characterized by multifocal islands of basaloid epithelium image resembling primitive follicles that are surrounded by a fibroblastic stroma.


TERMINOLOGY


Synonyms



  • Nevus sebaceus: Organoid nevus, Jadassohn nevus


Definitions



  • Nevus sebaceus



    • Hamartoma with abnormalities of epidermis, follicles, sebaceous glands, and apocrine glands


  • Basaloid follicular hamartoma (main type of follicular hamartoma)



    • Hamartoma that consists of proliferation of basaloid epithelium resembling primitive follicles


ETIOLOGY/PATHOGENESIS


Developmental Anomaly



  • Nevus sebaceus



    • Deletion of PTCH gene may play a role


  • Basaloid follicular hamartoma



    • Possible role for Sonic Hedgehog signaling pathway


CLINICAL ISSUES


Presentation



  • Nevus sebaceus



    • Usually presents in infancy, often at birth


    • Usually involves scalp


    • Less commonly on face


    • Presents as yellowish flat to warty plaque


    • Often enlarges during puberty


  • Follicular hamartomas



    • Solitary



      • Elderly patients


      • Face most common site


      • Flesh-colored papule


      • May clinically mimic basal cell carcinoma (BCC)


    • Localized



      • Presents in 3rd-4th decade


      • Presents on head as erythematous to hyperpigmented plaque


    • Linear nevoid



      • Large surface area with linear pattern


      • May follow dermatome


      • Pale brown plaque with follicular papules


    • Generalized



      • Infiltrative plaques on face


      • Associated with alopecia totalis and autoimmune disease: Lupus erythematosus and myasthenia gravis


    • Inherited



      • Autosomal dominant


      • Presents in adulthood with numerous flesh-colored or hyperpigmented papules on head and neck, trunk, and anogenital areas


      • May be associated with alopecia &/or cystic fibrosis


Treatment



  • Surgical approaches



    • Excision

Tags:
Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Nevus Sebaceus and Follicular Hamartomas

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