Sinonasal Melanoma



Sinonasal Melanoma


Lester D. R. Thompson, MD










Isolated junctional neoplastic cells are noted image in this MMM. The neoplastic cells in the stroma show pleomorphism and a plasmacytoid appearance. Pigment is easily identified.






High magnification shows a spindled to polygonal population of highly atypical, pigmented neoplastic cells. These changes are characteristic of melanoma.


TERMINOLOGY


Synonyms



  • Mucosal malignant melanoma (MMM)


  • Sinonasal tract mucosal malignant melanoma (STMMM)


Definitions



  • Neural crest-derived neoplasms originating from melanocytes and demonstrating melanocytic differentiation


ETIOLOGY/PATHOGENESIS


Environmental Exposure



  • Formalin


  • Possibly radiation


  • UV exposure


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Rare



      • Represents < 1% of all melanomas


      • < 5% of all sinonasal tract neoplasms


      • 15-33% of all skin melanomas occur in head and neck


      • STMMM represent < 4% of all head and neck melanomas


  • Age



    • Wide age range, usually in 5th-8th decades


  • Gender



    • Equal gender distribution


  • Ethnicity



    • Increased incidence in Japanese patients


Site



  • About 15-20% of melanomas arise in head and neck



    • 80% are cutaneous in origin


    • Ocular origin account for majority of remaining MMM


    • Sinonasal tract and oral cavity are next most common sites


  • Anterior nasal septum > maxillary sinus


Presentation



  • Nasal obstruction


  • Epistaxis or nasal discharge



    • Melanorrhea: Black-flecked (melanin) discharge


  • Polyp


  • Pain is uncommon


Treatment



  • Options, risks, complications



    • Metastatic melanoma to sinonasal tract can develop but is vanishingly rare


    • Breslow thickness and Clark level are not used in sinonasal tract


  • Surgical approaches



    • Wide local excision is treatment of choice


  • Radiation



    • Radiation can be used after surgery



      • In most cases, it is palliative


Prognosis



  • Overall prognosis is poor


  • 5-year survival: 17-47%


  • Recurrences are common


  • Poor prognosis associated with



    • Obstruction as presenting symptom


    • Nasopharynx or “mixed site” of involvement


    • Tumor ≥ 3 cm


    • Undifferentiated histology


    • High mitotic count


    • Recurrence


    • Stage of tumor


  • Matrix metalloproteinases (MMPs: Proteolytic enzymes required for extracellular matrix degradation) expression may be associated with patient outcome




    • Decreased MMP2 expression associated with greater overall survival


    • Positive MMP14 expression associated with poor survival


IMAGE FINDINGS


Radiographic Findings



  • Usually identifies extent of tumor and bone invasion


  • Positron emission tomography (PET) tends to show posterior nasal cavity and sinus tumors better than anterior nasal tumors


  • Locoregional and metastatic disease can be detected


MACROSCOPIC FEATURES


General Features



  • Most are polypoid


  • White to gray, brown, or black


  • Surface ulceration/erosion is common


Size



  • Range up to 6 cm


  • Mean: 2-3 cm


MICROSCOPIC PATHOLOGY


Histologic Features



  • Protean histology, mimic of many other primary tumor types


  • Junctional activity and intraepidermal migration (Pagetoid spread) help to confirm primary tumor


  • Surface ulceration is common, obscuring “in situ” component


  • Bone or soft tissue invasion is common


  • Many patterns of growth



    • Nests


    • Solid


    • Organoid


    • Sheets


    • Fascicles and interlacing bundles


    • Storiform


    • Meningothelial


    • Papillary


    • Hemangiopericytoma-like


    • Peritheliomatous: Distinctive and unique for STMMM


  • Variety of cell types can be seen



    • Undifferentiated


    • Epithelioid, polygonal


    • Small cell


    • Plasmacytoid


    • Rhabdoid


    • Giant cell


  • Vesicular nuclei, although sometimes hyperchromatic


  • Prominent, irregular, brightly eosinophilic, enlarged nucleoli


  • Intranuclear cytoplasmic inclusions usually present


  • Melanin-containing tumor cells can be seen


  • Tumor cell necrosis is common


  • Mitotic figures, including atypical forms, usually easily found


  • Inflammation may be present, but not of consequence


  • Desmoplastic type fibrosis can be seen, but is not common


  • Perineural invasion, when present, is poor prognostic indicator


  • Tumor depth of invasion (Clark) impossible to accurately assess


  • Tumor thickness (Breslow) not meaningful in sinonasal tract

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