Trichoblastoma



Trichoblastoma


David Cassarino, MD, PhD










Scanning magnification of a trichoblastoma shows a nodular basaloid proliferation associated with a fibrotic stroma. Note the presence of scattered folliculocystic structures image.






High magnification of a trichoblastoma shows a lobular basaloid proliferation associated with a cellular, fibrotic stroma image. Note the prominent stromal-stromal retraction artifact image.


TERMINOLOGY


Abbreviations



  • Trichoblastoma (TB)


Synonyms



  • Giant trichoepithelioma (TE)


  • Trichogerminoma


  • Rippled pattern trichomatricoma


  • Trichoblastic fibroma


  • Cutaneous lymphadenoma


Definitions



  • Benign dermal-based adnexal tumor showing primitive follicular differentiation


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Uncommon tumors


  • Age



    • Usually occur in adults


Site



  • Head and neck area, especially the scalp


Presentation



  • Dermal nodule/mass lesion



    • Usually single but may rarely be multiple


  • Usually asymptomatic


Treatment



  • Surgical approaches



    • Complete excision is curative


    • Should be recommended in cases of partial biopsy in order to exclude basal cell carcinoma (BCC)


Prognosis



  • Excellent in most cases


  • Rare recurrences and association with, or progression to, malignancy (BCC)


MACROSCOPIC FEATURES


General Features



  • Nodular lesion involving the deep dermis and subcutis


Size



  • Large, typically > 1 cm in diameter


MICROSCOPIC PATHOLOGY


Histologic Features



  • Large, basaloid-appearing deep dermal-based nodule



    • Usually symmetric and shows well-circumscribed borders


    • Composed of irregular lobules and nests of basaloid cells


    • No epidermal connections


    • May extend into superficial subcutis


  • Associated fibrotic stroma with increased numbers of fibroblasts



    • Stromal amyloid may be present


    • Calcifications and granulomatous inflammation occasionally seen but less common than in TE


  • Papillary mesenchymal bodies classically present, similar to TE



    • Invagination of fibroblastic stroma into primitive follicular structures


    • Represents abortive follicular induction


Subtypes



  • Trichogerminoma



    • Tightly packed lobules of primitive basaloid cells with minimal stroma


  • Rippled pattern trichomatricoma



    • Palisading ribbons of basaloid cells; may resemble Verocay bodies



  • Trichoblastic fibroma



    • Less epithelial structures, more prominent stroma, which may appear desmoplastic


  • Cutaneous lymphadenoma



    • Rare variant with a prominent lymphocytic infiltrate and clear cell features


DIFFERENTIAL DIAGNOSIS


Basal Cell Carcinoma



  • BCC usually shows multiple attachments to the overlying epidermis (focal or absent in TB)


  • BCC also shows the following features (which are not seen in TB)



    • Prominent peripheral palisading


    • Mucinous stroma


    • Tumor-stromal retraction artifact (stromal-stromal retraction seen in TB)


    • Numerous mitotic and apoptotic figures


  • Immunohistochemistry may be useful in some cases (particularly small, partial biopsies)



    • Bcl-2, p53, and Ki-67 all elevated in BCC (should be low in TB)


    • CK20 highlights Merkel cells in TB (absent in BCC)


Trichoepithelioma



  • Small, papular lesion clinically


  • Overlapping histologic features, but TE is smaller, more superficial than TB


  • Usually shows more prominent folliculocysts, calcifications, and granulomatous inflammation


Sebaceoma



  • More superficial, epidermal- or follicular-based adnexal neoplasm


  • Composed of lobules and nests of predominantly basaloid cells with minor population of clear cells


  • May show rippled pattern with nuclear palisading, similar to rippled pattern trichomatricoma


  • Scattered mature sebaceous cells with multivacuolated cytoplasm


Cylindroma



  • Dermal-based neoplasm composed of basaloid cells with ductal differentiation


  • Irregular, “jigsaw puzzle” pattern of variably shaped lobules and nests



    • Surrounded by hyalinized basement membrane, and nests contain hyalinized globules


  • Focal ductal lumina present (may be highlighted by EMA &/or CEA)

Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Trichoblastoma
Premium Wordpress Themes by UFO Themes
%d bloggers like this: