Sebaceous Carcinoma



Sebaceous Carcinoma


David Cassarino, MD, PhD










Scanning magnification of a sebaceous carcinoma shows a very large, nodular tumor in the dermis. Note the lack of epidermal attachments; however, there are focal entrapped follicular structures image.






Higher power examination of a sebaceous carcinoma shows a proliferation of markedly atypical clear cells with numerous mitotic figures image and abundant apoptotic cellular debris image.


TERMINOLOGY


Synonyms



  • Sebaceous adenocarcinoma


Definitions



  • Malignant adnexal tumor of sebaceous cells


  • Often lacks clear cell features in poorly differentiated cases and may show basaloid or squamoid features, leading to high incidence of misdiagnosis


ETIOLOGY/PATHOGENESIS


Unknown in Most Cases



  • Some cases likely due to solar (UV) damage, as most occur on sun-damaged skin of elderly


Genetic



  • Strong association with Muir-Torre syndrome (MTS) in patients who have multiple sebaceous tumors &/or multiple keratoacanthomas and internal organ malignancies



    • Genes implicated include MLH1, MSH2, MSH6



      • Encode mismatch repair proteins


      • Mutations lead to microsatellite instability (MSI)


      • MSI assays and immunohistochemistry can be used to screen for Muir-Torre syndrome


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Uncommon tumors, but one of the more common types of adnexal carcinoma


  • Age



    • Most occur in elderly patients


  • Gender



    • Females have slightly higher incidence


Site



  • Eyelids are by far the most common site (˜ 75% of cases)


  • Remainder of cases occur in other head and neck sites, followed by trunk, extremities


Presentation



  • Nodular, firm, yellow-tan lesions


  • Often ulcerated


Treatment



  • Surgical approaches



    • Complete excision is necessary to ensure local removal


    • Mohs excision is reported to be effective in most cases


    • Sentinel lymph node biopsy may be useful for staging purposes


Prognosis



  • Aggressive tumors with high incidence of metastasis (> 30% of cases) and generally poor prognosis unless discovered early


MACROSCOPIC FEATURES


General Features



  • Dermal-based firm, nodular lesion


Size



  • Usually 1-4 cm


MICROSCOPIC PATHOLOGY


Histologic Features



  • Dermal-based infiltrative, nodular to sheet-like tumor


  • Often with focal follicular &/or epidermal connections



    • Pagetoid involvement of epidermis may be seen in up to 30% of cases



  • Tumor consists of variably differentiated epithelioid cells



    • Clear cells often present but vary greatly in number


    • Well-differentiated tumors show prominent clear cell changes



      • Cells contain abundant cytoplasmic lipid, often producing multiple vacuoles and nuclear indentation


      • Nuclei are enlarged and vesicular or hyperchromatic-staining, with prominent nucleoli


    • Moderately and poorly differentiated tumors show few to rare clear cells



      • May be composed predominantly of basaloid or squamoid cells


      • Show prominent cytologic atypia and pleomorphism


      • Mitotic figures, including atypical forms, are usually abundant


    • Areas of necrosis, with comedonecrosis pattern, are common


    • Lymphovascular invasion present in significant percentage of cases


Cytologic Features



  • Enlarged, epithelioid cells with abundant cytoplasm and hyperchromatic or vesicular nuclei with enlarged nucleoli



    • Clear cells usually show cytoplasmic vacuoles and nuclear indentation


    • However, cells can also be basaloid (common) or squamoid (rare)


ANCILLARY TESTS


Histochemistry



  • Sudan black B and oil red O (need frozen tissue)



    • Reactivity: Positive


    • Staining pattern



      • Cytoplasmic staining


  • Periodic acid-Schiff



    • Reactivity: Usually negative (indicating lack of glycogen)


Immunohistochemistry

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