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Tumors with Myoepithelial Differentiation

Synonyms: Myoepitheliomas

Definition

Tumors composed exclusively of myoepithelial cells which may show spindle, hyaline (plasmacytoid) or clear cell morphology.

Clinical Features

  • Most spindle cell and clear cell myoepitheliomas in parotid
  • Most pure hyaline myoepitheliomas in minor salivary glands, particularly in palate1,2
  • Range of differentiation

Histopathology

Spindle Cell Myoepithelioma

  • Stroma-like appearance:
    • can be confused with lesions of fibroblasts, Schwann cells, or smooth muscle cells (Fig. 1
      Spindle cell myoepithelioma of parotid gland. It would be very difficult to distinguish this tumor from a soft tissue neoplasm on purely morphologic grounds.

      Fig. 1: Spindle cell myoepithelioma of parotid gland. It would be very difficult to distinguish this tumor from a soft tissue neoplasm on purely morphologic grounds.

      )6
    • in variant oncocytic myoepithelioma cytoplasm has granular oxyphilic quality7
  • Scanty collagen stroma
  • May be:
  • Ultrastructurally:
    • microfilaments of actin and keratin type11 (Fig. 2
      Electron micrograph of a myoepithelioma of parotid gland. Portion of a neoplastic myoepithelial cell illustrating (left to right) extracellular space with collagen fibrils and basement membrane, electron-dense attachment plaques on the cell membrane, linear arrays of 6nm actin microfilaments, perinuclear bundles of tonofilaments (indicative of squamous metaplasia), and a portion of the nucleus. (× 22,900) (Courtesy of Dr Robert A. Erlandson, Memorial Sloan-Kettering Cancer Center)

      Fig. 2: Electron micrograph of a myoepithelioma of parotid gland. Portion of a neoplastic myoepithelial cell illustrating (left to right) extracellular space with collagen fibrils and basement membrane, electron-dense attachment plaques on the cell membrane, linear arrays of 6nm actin microfilaments, perinuclear bundles of tonofilaments (indicative of squamous metaplasia), and a portion of the nucleus. (× 22,900) (Courtesy of Dr Robert A. Erlandson, Memorial Sloan-Kettering Cancer Center)

      )

Hyaline Cell Myoepithelioma

  • Composed of hyaline cells with:
    • eccentric nuclei
    • some pleomorphism and hyperchromasia
    • scanty or no mitotic activity
    • abundant cytoplasm with a diffuse eosinophilia
  • Cell margins polygonal and sharply outlined (Fig. 3
    Myoepithelioma composed of ‘hyaline cells'. (H&E)

    Fig. 3: Myoepithelioma composed of ‘hyaline cells'. (H&E)

    )
  • Hyaline cells may simulate neoplastic plasma cells or skeletal muscle cells
  • Ultrastructurally:
    • abundant uniformly dispersed microfilaments 50–100Å in diameter12

Clear Cell Myoepithelioma

  • Composed of small tubules:
    • lined by single layer of small cuboidal cells surrounded by one or more layers of prominent clear cells with hyaline-like material in between (Fig. 4
      Epithelial–myoepithelial carcinoma. The myoepithelial component is represented by the cells with clear cytoplasm.

      Fig. 4: Epithelial–myoepithelial carcinoma. The myoepithelial component is represented by the cells with clear cytoplasm.

      )
  • Clear cells contain:
    • variable amounts of glycogen
    • no fat or mucin
  • In some areas scanty ductal formations:
    • lesion appears as sheet of clear cells13
  • Sometimes a focal high-grade carcinomatous component in an otherwise typical epithelial–myoepithelial carcinoma14

Special Stains and Immunohistochemistry

  • Neoplastic myoepithelial cells:
  • Immunohistochemical profile shows:
    • differences related to myoepithelioma subtype23
    • heterogeneity within each category19,24

Diagnosis

Prognosis

References

1 Kuwabara H, Uda H, Miyabe K, Saito K, Shibanushi T. Malignant plasmacytoid myoepithelioma of the palate: histological observations compared to benign predominant plasmacytoid myoepithelial cells in pleomorphic adenoma of the palate. Ultrastruct Pathol. 1998;22:153–160.

2 Lomax-Smith JD, Azzopardi JG. The hyaline cell. A distinctive feature of “mixed” salivary tumors. Histopathology. 1978;2:77–92.

3 Di Palma S, Guzzo M. Malignant myoepithelioma of salivary glands. Clinicopathological features of ten cases. Virchows Arch [A]. 1993;423:389–396.

4 Suzuki H, Inoue K, Fujioka Y, Ishikura H, Furuta Y, Fukuda S. Myoepithelial carcinoma with predominance of plasmacytoid cells arising in a pleomorphic adenoma of the parotid gland. Histopathology. 1998;32:86–87.

5 Chetty R. Intercalated duct hyperplasia: possible relationship to epithelial-myoepithelial carcinoma and hybrid tumours of salivary glands. Histopathology. 2000;37:260–263.

6 Chaudhry AP, Satchidanand S, Peer R, Cutler LS. Myoepithelial cell adenoma of the parotid gland. A light and ultrastructural study. Cancer. 1982;49:288–293.

7 Skàlovà A, Michal M, Ryska A, Simpson RH, Kinkor Z, Walter J, et al. Oncocytic myoepithelioma and pleomorphic adenoma of the salivary glands. Virchows Arch. 1999;434:537–546.

8 Sciubba JJ, Brannon RB. Myoepithelioma of salivary glands. Report of 23 cases, Cancer. 1982;49:562–572.

9 Skàlovà A, Stàrek I, Simpson RH, Kucenovà V, Dvorackovà J, Curik R, et al. Spindle cell myoepithelial tumours of the parotid gland with extensive lipomatous metaplasia. A report of four cases with immunohistochemical and ultrastructural findings. Virchows Arch. 2001;439:762–767.

10 Skalova A, Michal M. Biphasic myoepithelioma of parotid gland with collagenous crystalloids. Histopathology. 1994;24:583–586.

11 Takai Y, Mori M, Dardick I, MacKay A, Leung R, Wattimena D, et al. Myofilament localization and immunoelectron microscopic detection of muscle-specific actin in neoplastic myoepithelial cells in pleomorphic adenomas and myoepitheliomas. Ultrastruct Pathol. 1994;18:575–591.

12 Stromeyer FW, Haggitt RC, Nelson JF, Hardman JM. Myoepithelioma of minor salivary gland origin. Light and electron microscopical study. Arch Pathol. 1975;99:242–245.

13 Michal M, Skàlovà A, Simpson RH, Rychterova V, Leivo I. Clear cell malignant myoepithelioma of the salivary glands. Histopathology. 1996;28:309–316.

14 Alos L, Carrillo R, Ramos J, Baez JM, Mallofre C, Fernandez PL, et al. High-grade carcinoma component in epithelial-myoepithelial carcinoma of salivary glands: clinicopathological, immunohistochemical and flow-cytometric study of three cases. Virchows Arch. 1999;434:291–300.

15 Dardick I, Ostrynski VL, Ekem JK, Leung R, Burford-Mason AP. Immunohistochemical and ultrastructural correlates of muscle-actin expression in pleomorphic adenomas and myoepitheliomas based on comparison of formalin and methanol fixation. Virchows Arch [A]. 1992;42:95–104.

16 Hara K, Ito M, Takeuchi J, Iijima S, Endo T, Hidaka H. Distribution of S-100b protein in normal salivary glands and salivary gland tumors. Virchows Arch [A]. 1983;401:237–249.

17 Kahn HJ, Baumal R, Marks A, Dardick I, van Nostrand AWP. Myoepithelial cells in salivary gland tumors. An immunohistochemical study. Arch Pathol Lab Med. 1985;109:190–195.

18 Luna MA, Ordóñez NG, Mackay B, Batsakis JG, Guillamondegui O. Salivary epithelial-myoepithelial carcinomas of intercalated ducts. A clinical, electron microscopic, and immunocytochemical study. Oral Surg Oral Med Oral Pathol. 1985;59:482–490.

19 Mori M, Ninomiya T, Okada Y, Tsukitani K. Myoepitheliomas and myoepithelial adenomas of salivary gland origin. Immunohistochemical evaluation of filament proteins, S-100 alpha and beta, glial fibrillary acidic proteins, neuron-specific enolase, and lactoferrin. Pathol Res Pract. 1989;184:168–178.

20 Nilsen R, Donath K. Actin containing cells in normal human salivary glands. An immunohistochemical study. Virchows Arch [A]. 1981;391:315–322.

21 Palmer RM. The identification of myoepithelial cells in human salivary glands. A review and comparison of light microscopical methods. J Oral Pathol. 1986;15:221–229.

22 Jones H, Moshtael F, Simpson RH. Immunoreactivity of alpha smooth muscle actin in salivary gland tumours. A comparison with S100 protein. J Clin Pathol. 1992;45:938–940.

23 Foschini MP, Scarpellini F, Gown AM, Eusebi V. Differential expression of myoepithelial markers in salivary, sweat and mammary glands. Int J Surg Pathol. 2000;8:29–37.

24 Morinaga S, Nakajima T, Shimosato Y. Normal and neoplastic myoepithelial cells in salivary glands. An immunohistochemical study. Hum Pathol. 1987;18:1218–1226.

25 Batsakis JG, El-Naggar AK. Myoepithelium in salivary and mammary neoplasms is host-friendly. Adv Anat Pathol. 1999;6:218–226.

26 Dardick I, Thomas MJ, van Nostrand AW. Myoepithelioma—new concepts of histology and classification. A light and electron microscopic study. Ultrastruct Pathol. 1989;13:187–224.

27 Hubner G, Klein HJ, Kleinsasser O, Schieffer HG. Role of myoepithelial cells in the development of salivary gland tumors. Cancer. 1971;27:1255–1261.

28 Prasad AR, Savera AT, Gown AM, Zarbo RJ. The myoepithelial immunophenotype in 135 benign and malignant salivary gland tumors other than pleomorphic adenoma. Arch Pathol Lab Med. 1999;123:801–806.

29 Simpson RHW, Jones H, Beasley P. Benign myoepithelioma of the salivary glands. A true entity? Histopathology. 1995;27:1–9.

30 Franquemont DW, Mills SE. Plasmacytoid monomorphic adenoma of salivary glands. Absence of myogenous differentiation and comparison to spindle cell myoepithelioma. Am J Surg Pathol. 1993;17:146–153.

31 Dardick I, Cavell S, Boivin M, Hoppe D, Parks WR, Stinson J, et al. Salivary gland myoepithelioma variants. Histological, ultrastructural, and immunocytological features. Virchows Arch [A]. 1989;416:25–42.

32 Fonseca I, Soares J. Proliferating cell nuclear antigen immunohistochemistry in epithelial-myoepithelial carcinoma of the salivary glands. Arch Pathol Lab Med. 1993;117:993–995.

33 Tanimura A, Nakamura Y, Nagayama K, Tanaka S, Hachisuka H. Myoepithelioma of the parotid gland. Report of two cases with immunohistochemical technique for S-100 protein and electron microscopic observation. Acta Pathol Jpn. 1985;35:409–417.

34 Barnes L, Appel BN, Perez H, El-Attar AM. Myoepitheliomas of the head and neck. Case report and review. J Surg Oncol. 1985;28:21–28.

35 Brocheriou C, Auriol M, de Roquancourt A, Gaulard P, Fornes P. Epithelial-myoepithelial carcinoma of the salivary glands. Study of 15 cases and review of the literature. Ann Pathol (France). 1991;11:316–325.

36 Crissman JD, Wirman JA, Harris A. Malignant myoepithelioma of the parotid gland. Cancer. 1977;40:3042–3049.

37 Fonseca I, Soares J. Epithelial-myoepithelial carcinoma of the salivary glands. A study of 22 cases. Virchows Arch [A]. 1993;422:389–396.

38 Nagao T, Sugano I, Ishida Y, Tajima Y, Matsuzaki O, Konno A, et al. Salivary gland malignant myoepithelioma: a clinicopathologic and immunohistochemical study of ten cases. Cancer. 1998;83:1292–1299.

39 Savera AT, Sloman A, Huvos AG, Klimstra DS. Myoepithelial carcinoma of the salivary glands: A clinicopathologic study of 25 patients. Am J Surg Pathol. 2000;24:761–774.

40 Luna MA, Batsakis JG, Ordóñez NG, Mackay B, Tortoledo ME. Salivary gland adenocarcinomas. A clinicopathologic analysis of three distinctive types. Semin Diagn Pathol. 1987;4:117–135.

Last updated: 8 Jan 2006

Tumors with Myoepithelial Differentiation

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