Case 233 - Discussion

Uploaded: 2008-05-20, Updated: 2008-05-20

Diagnosis: Myoepithelioma (Spindle Cell Variant) or Myoepithelial Carcinoma?

Myoepithelioma

CLINICAL FEATURES

  • 1.5% of all salivary gland tumors; most commonly in parotid gland (40%), then hard and soft palate (21%).

  • M=F; average age, 44 years.

GROSS FINDINGS

  • Well-demarcated with a solid, tan or yellow-tan glistening cut surface.

MICROSCOPIC FINDINGS

  • Encapsulated with a fibrous capsule in various thickness.

  • Sheets and islands of various proportions of spindle cells, plasmacytoid, epithelioid, or clear cells.

  • Rare or no ducts.

  • May have abundant acellular, mucoid or hyalinized stroma, but no chondroid or myxochondroid foci.

DIFFERENTIAL DIAGNOSES

  • Mixed adenoma, nerve sheath tumor, fibrous histiocytoma, nodular fasciitis, leiomyoma, and synovial sarcoma.

IMMUNOHISTOCHEMISTRY AND SPECIAL STAINS

  • Cytokeratin: consistently positive, especially CK14;

  • SMA: consistent expression

  • S100: limited expression

  • GFAP: occasionally

  • Vimentin.

REFERENCES

  • AFIP, tumor of the adrenal glands and extra-adrenal paraganglia, series 3;