Myopericytoma



Myopericytoma


Thomas Mentzel, MD










Clinical photograph shows a raised nodular lesion mimicking a vascular neoplasm arising on the lower leg of an adult male patient.






Hematoxylin & eosin shows a perivascular myoid neoplasm characterized by a concentric perivascular growth of myogenic tumor cells.


TERMINOLOGY


Synonyms



  • Hemangiopericytoma


Definitions



  • Benign perivascular neoplasm composed of perivascular myoid tumor cells (myopericytes)


  • Myopericytoma forms morphologic spectrum with angioleiomyoma, myofibroma, and glomus tumor


CLINICAL ISSUES


Epidemiology



  • Incidence



    • Rare


  • Age



    • Arises most commonly in mid-adulthood


    • Children are rarely affected


Site



  • Arises most commonly in dermal/subcutaneous tissues


  • Arises rarely in deep soft tissues


  • Distal extremities are most frequently involved



    • Proximal extremities, such as neck and trunk, more rarely involved


  • Rare malignant examples usually arise in deep soft tissues


Presentation



  • Painless mass



    • Usually solitary lesions


    • Multiple lesions are very rare


  • Slow-growing


  • Subcutaneous mass


Natural History



  • Often longstanding neoplasms


  • No increased number of local recurrences


Treatment



  • Surgical approaches



    • Complete excision


Prognosis



  • Most lesions do not recur


  • Local recurrences are related to poor circumscription


  • Very rare malignant myopericytomas characterized by poor clinical outcome


MACROSCOPIC FEATURES


General Features



  • Nodular indurated lesions


  • Variable number of vessels


MICROSCOPIC PATHOLOGY


Histologic Features



  • Numerous thin-walled blood vessels


  • Perivascular multilayered concentric growth


  • Plump spindled &/or round myoid tumor cells


  • Tumor cells with eosinophilic or amphophilic cytoplasm


  • Round, plump, spindled nuclei


  • Mitoses are rare


  • May show focal areas similar to glomus tumor, angioleiomyoma, or myofibroma


  • Areas of infarction and hemorrhage especially in deepseated neoplasms


  • Degenerative atypia may be present in longstanding neoplasms


  • Prominent degenerative stromal changes in longstanding neoplasms


  • May show prominent myxoid stromal changes


  • Variable morphologic features


  • Classic solid variant



    • Narrow, closely packed vessels



    • Vessels are concentrically surrounded by spindled &/or round tumor cells


  • Hemangiopericytoma-like variant



    • Dilated, branching, thin-walled vessels


    • Perivascular growth of myoid tumor cells


  • Angioleiomyoma-like variant



    • Perivascular growth of elongated spindled cells


  • Intravascular variant



    • Intravascular or intramural growth


    • Closely packed, thin-walled vessels


    • Vessels are concentrically surrounded by myoid tumor cells


  • Malignant variant



    • Infiltrative growth


    • Prominent cytologic atypia


    • Numerous mitoses


    • Areas of tumor necrosis


  • Rare hypocellular fibroma-like variant


  • Rare immature cellular variant


Predominant Pattern/Injury Type



  • Circumscribed


  • Hemangiopericytic


Predominant Cell/Compartment Type



  • Mesenchymal



    • Myoid tumor cells


ANCILLARY TESTS


Cytogenetics



  • Characteristic t(7;12)(p21-22;q13-15)


  • ACTB-GLI fusion


DIFFERENTIAL DIAGNOSIS


Myofibroma



  • Biphasic growth



    • Undifferentiated mesenchymal tumor cells associated with numerous thin-walled vessels showing hemangiopericytoma-like growth


    • Mature, spindled, eosinophilic tumor cells


  • Often multinodular growth


  • Myxohyaline stromal changes


  • HCAD(-): Rarely focal positivity


Angioleiomyoma



  • Thick-walled vessels


  • Predominance of spindled eosinophilic tumor cells


  • Usually desmin(+)

Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Myopericytoma
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