The hyaline cell: a distinctive feature of ‘mixed’ salivary tumours

Abstract

We have identified and described a distinctive type of cell which is characteristic of the "mixed" salivary tumour. This "hyaline cell" or plasmacytoid cell is particularly common and conspicuous in "mixed" tumours of the palate and other sites in the mouth. It occurs also in tumours of the major glands, but with much lesser frequency. The hyaline cell is found in "mixed" salivary-type tumours in other sites, e.g. the skin. It is not present in the other types of salivary tumour, notably adenoid cystic carcinoma, adenolymphoma, mucoepidermoid and acinic tumour. Ultrastructural study suggests that the hyaline cell is an indicator of myoepithelial differentiation. Current concepts of the acceptable pathways of myoepithelial differentiation in "mixed" tumours are discussed briefly. The specificity of the hyaline cell will probably prove valuable in separating "mixed" tumours from monomorphic adenomas, thus retaining the identity of the latter. The hyaline cell is almost as distinctive a feature of "mixed" tumours as is myxochondroid tissue and its specificity is of practical value in the diagnosis and classification of salivary tumours.

Myoepitheliomas of the skin and soft tissues

“…Epithelioid myoepithelial cells in 2 cases revealed copious hyaline cytoplasm ( Fig. 4) and had the appearance of the so-called hyaline cells in salivary gland tumours [20]. The transitions between the spindle and epithelioid myoepithelial cells were usually gradual, and in 3 cases the shape and arrangement of the myoepithelial cells resembled those seen in synovial sarcoma (Fig.…”

Plasmacytoid cells in salivary-gland pleomorphic adenomas: evidence of luminal cell differentiation

“…Due to misinterpretation of these filaments as actin microfilaments, they were originally thought to be neoplastic MECs [27,29,42,43,50]. Though the filaments have been proved to be intermediate filaments, plasmacytoid cells are still considered neoplastic MECs because they are members of the non-luminal cells in pleomorphic adenomas [13].…”

“…They are oval to polygonal cells with an eccentrically placed nucleus and an eosinophilic hyaline cytoplasm. They are also the cellular constituents of pleomorphic adenoma [8,20,29]. Because previous studies have not observed the MEC character in plasmacytoid cells [13,14,21,33,38,40], we decided to seek the non-MEC character in these cells.…”

Pathology of the salivary glands: The contribution of electron microscopy

“…3B; Lam, 1985) and accounting for the varying amounts of myxochondroid or collagenous "stroma". In some pleomorphic adenomas, there will be a relative balance between luminal and modified myoepithelial cells, whereas in others these tumor cells may predominate with more or less differentiation as chondrocytes (Dardick et al, 1983b;Mills and Cooper, 1981 (Lomax-Smith and Azzopardi, 1978;Sciubba and Brannon, 1982) is produced (Fig. 4B).…”