myoepithelioma


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  • Names

    • mixed tumor
    • myoepithelioma
    • parachordoma

  • Clinical

    • soft tissue sites: extremities. Also head/neck, trunk.
    • salivary gland sites: parotid (40%), minor glands

  • Histology

    • architecture: nests, cords, ductules
    • cytology: epithelioid, spindled, or plasmacytoid cells. Pink to clear cytoplasm, minimal pleomorphism, scant mitosis (< 2 per 10 hpf)
      • plasmacytoid more often in minor salivary glands, mimicks rhabdoid appearance
    • myoepithelioma: plasmacytoid to spindled myoepithelial cells
    • mixed tumor: has ductal elements
    • parachordoma: has prominent cytoplasmic vacuolation
    • stroma: hyalinized to chondromyxoid
    • can have metaplasia: squamous, fat, bone, cartilage

  • Stains

    • positive: CK, vimentin, S100
    • variable: calponin, SMA, GFAP, desmin, EMA

  • Ddx

    • myoepithelial rich pleomorphic adenoma
    • myoepithelial carcinoma
      • invasive
    • other soft tissue neoplasms
      • CK-
    		•