Myoepithelioma/Mixed Tumor/Parachordoma

Myoepithelioma/Mixed Tumor/Parachordoma

Thomas Mentzel, MD

Grossly, this myoepithelioma arising in deep soft tissues represents a rather well-circumscribed, nodular neoplasm with gray-white cut surfaces.

Plasmacytoid myoepithelial tumor cells are arranged in clusters and solid areas and set in a myxohyaline stroma in this example of myoepithelioma of deep soft tissues.



  • Ectomesenchymal chondromyxoid tumor (of tongue)


  • Neoplasms composed of epithelial &/or myoepithelial cellular elements in varying proportions

    • Tumor cells are set in hyalinized to chondromyxoid stroma and may show foci of ductal differentiation

  • Show overlap with mixed tumor of skin and soft tissues

  • Show overlap with myoepithelial carcinoma (malignant myoepithelioma) of skin and soft tissues



  • Incidence

    • Rare neoplasms

    • Increasingly reported

  • Age

    • Arise usually in adults

    • Significant number of cases arise in children < 10 years old

  • Gender

    • Slight male predominance


  • Subcutaneous and deep soft tissue

  • Rare in skin

  • Very rare in bone

  • Upper > lower extremities > head/neck region > trunk

  • Less commonly on trunk and in head/neck region


  • Painless mass


  • Surgical approaches

    • Complete excision


  • Most neoplasms behave in benign fashion

  • Minority of cases may recur locally and metastasize

    • Benign-appearing neoplasms recur in < 20% of cases and do not metastasize

  • At present, no morphologic features reliably predict prognosis

  • Cytologic atypia represents most reliable prognostic parameter

  • Obvious malignant neoplasms behave aggressively

    • Metastases have been reported in up to 30% of cases


General Features

  • Usually well-circumscribed neoplasms


Histologic Features

  • Nodular or lobular growth

  • Characterized by variable morphology

  • Varying proportions of epithelioid cells, spindled cells, plasmacytoid cells, clear cells

  • Cytoplasmic vacuolation is prominent in parachordoma-like cases

  • Neoplastic cells are arranged in nests, cords, solid formations

  • Ductal structures are not or only focally present

  • Tumor cells are embedded in hyalinized to chondromyxoid stroma

  • Divergent differentiation (squamous, adipocytic, cartilaginous, osseous) may be present

  • Nuclear pleomorphism is generally minimal

  • Few mitoses are usually present (< 2 mitoses per 10 high-power fields)

  • Dedifferentiation (progression) into frank myoepithelial carcinoma or sarcoma is seen rarely

  • May show loss of INI1 expression in considerable number of cases

  • Cutaneous myoepithelioma

    • Rare neoplasms

    • No ductal differentiation (vs. chondroid syringoma)

    • Form spectrum with chondroid syringoma and malignant myoepithelioma of skin

    • No connection with overlying epidermis

    • May infiltrate into subcutis

    • Broad variation in regard to growth patterns and cytomorphology

    • Local recurrences are rare

    • Lymph node metastases are very rare

      • Show increased atypia and proliferative activity

  • Malignant myoepithelioma (myoepithelial carcinoma)

    • Very rare neoplasms

    • Tend to be large

    • Severe cytologic atypia

    • Pleomorphic tumor cells

    • Increased proliferative activity

    • Tumor necrosis

    • Metastasize in up to 30% of cases (pulmonary and nodal metastases)

Cytologic Features

Jul 9, 2016 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Myoepithelioma/Mixed Tumor/Parachordoma

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