Melanotic Schwannoma



Melanotic Schwannoma


Ayca Ersen, MD

Bernd W. Scheithauer, MD





Key Facts


Clinical Issues



  • Sporadic or syndromic (Carney complex)


Macroscopic Features



  • No encapsulation; occasionally interrupted, thin collagen layer with soft tissue invasion


Microscopic Pathology



  • Delicate chromatin/small nucleoli/rare mitoses (benign)


  • Vesicular nuclei/coarse chromatin/violaceous macronucleoli, frequent mitoses (malignant)


  • Pigmentation variable or patchy


  • Plus psammomatous calcifications in psammomatous variant


Ancillary Tests



  • Reticulin outlines lobules


  • S100, HMB-45, Melan-A, tyrosinase positive


  • Collagen IV and laminin outline basal lamina around lobules


Top Differential Diagnoses



  • Conventional schwannoma



    • Contain lipofuchsin (PAS[+]) but lack melanin


  • Pigmented neurofibroma



    • Typically diffusely infiltrative


  • Melanocytoma



    • Lack long-spacing collagen


  • Primary or metastatic melanoma



    • Cytologically malignant


  • Clear cell sarcoma (soft tissue melanoma)



    • No immunohistochemical or ultrastructural basal lamina







Circumscribed and ovoid like other schwannomas, melanocytic variants are variably pigmented, extremely so in this case.






Pigmented spindle-shaped or epithelioid cells often form lobules.


TERMINOLOGY


Synonyms



  • Pigmented schwannoma


  • Melanogenic schwannoma


  • Melanogenic nerve sheath tumor


Definitions



  • Usually benign, often circumscribed tumor of melanin-producing Schwann cells


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Sporadic


    • Syndromic (Carney complex)



      • Frequent mutation of tumor suppressor gene PRKAR1A


  • Age



    • Childhood to senescence (mean: 35 years)



      • A decade younger in patients with Carney complex


  • Gender



    • Slight female predominance (1.5:1) in both sporadic and syndromic types


Site



  • Sporadic



    • Spinal nerves and ganglia (cervicothoracic)


    • Rarely multiple


  • Syndromic (Carney complex)



    • Alimentary tract


    • Viscera (heart, liver, lung)


    • Bone


    • 15% multiple


Presentation



  • Sporadic



    • Nerve root associated tumors: Pain or sensory disturbance


  • Syndromic (Carney complex; autosomal dominant)



    • Psammomatous melanotic schwannoma: Mass effects


    • Lentigines (65%) of face, lips, caruncle, and female genitalia


    • Myxomas of heart (65%), skin (25%), breast (20%)


    • Blue nevi of extremities and trunk


    • Endocrine overactivity



      • Cushing syndrome (25%): Pigmented nodular adrenocortical disease


      • Acromegaly: Pituitary adenoma, mammosomatotrophic type


      • Precocious puberty (30%): Large cell Sertoli tumor of testis


Treatment



  • Surgical approaches



    • Resection with tumor-free margins for all lesions


Prognosis



  • Benign



    • Recurrence in subtotal resection


  • Malignant



    • Metastasis



      • Distinguish metastases from 2nd primary


      • Prognosis same in conventional and psammomatous variants


      • 15% die of tumor


IMAGE FINDINGS


MR Findings



  • MR features depend on paramagnetic free radicals in melanin



    • Hyperintense on T1-weighted MR


    • Hypointense in T2-weighted MR


  • Contrast enhancing



  • Solid > cystic


  • Demarcated, ± nerve association


  • Benign tumors may erode bone (spinal foramina)


  • Malignant tumors less demarcated; invasive destruction of bone


CT Findings



  • Calcification/ossification on CT in some psammomatous tumors


MACROSCOPIC FEATURES


General Features



  • 0.5-26 cm (median: 5 cm)


  • Circumscribed


  • Round to sausage-shaped



    • Spinal nerve root tumors: Dumbbell-shaped


  • Occasionally lobulated or cystic


  • No encapsulation



    • Occasionally thin collagen layer with soft tissue invasion


  • Effects of bone



    • Erosion (benign tumors)


    • Invasive destruction (malignant tumors)


  • Cut surface gray to tar black



    • Infrequently cystic


    • Occasional hemorrhage or necrosis


    • Occasional subcapsular grittiness (psammomatous variant)


  • Soft to rubbery; occasionally hard


  • Maybe multifocal, usually when malignant


MICROSCOPIC PATHOLOGY


Histologic Features

Tags:
Jul 8, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Melanotic Schwannoma

Full access? Get Clinical Tree
Get Clinical Tree app for offline access