Crystalloids in salivary gland pleomorphic adenomas

Two types of crystalloids in salivary gland pleomorphic adenomas were studied by light microscopy and electron microscopy. The first type of crystalloid, the previously described tyrosine-rich crystalloid, was identified in three (1.5%) of 205 cases. The crystalloids by light microscopy assumed a radial configuration, resulting in the characteristic petal-shaped morphology. Transmission electron microscopy revealed them to be electron-dense, lobular projections without internal structure. Scanning electron microscopy demonstrated a range of morphology from rounded and intact doughnutlike structures to aggregates of irregular, loosely cohesive plates. The crystalloids were backscatter positive by backscattered electron imaging, and by x-ray microanalysis exhibited prominent calcium, phosphorus, and magnesium peaks that were not present in the adjacent tumor tissue; these three elements may be important in the formation and structure of tyrosine-rich crystalloids. The second type of crystalloid was intraductal and birefringent and was identified in 26 (12.7%) of 205 cases. In 21 of these 26 cases the crystalloids were lost on 10% formaldehyde fixation and paraffin embedding. Histochemical stains and x-ray microanalysis did not reveal a definite chemical composition, but did suggest a predominantly organic nature.     

Epithelial–mesenchymal transdifferentiation and extracellular matrix gene expression in pleomorphic adenomas of the parotid salivary gland

Mesenchymal and epithelial cell differentiation are assumed to be dichotomic primary events in embryonic development. In this study, pleomorphic adenomas of the parotid gland were analysed as a model which shows morphological features of both epithelial and mesenchymal tissue types. Using matrix gene expression profiles as a supplementary criterion for the identification of cellular phenotypes, areas with unequivocal epithelial and mesenchymal differentiation could be demonstrated. Many areas displayed a transitional phenotype with cells showing both epithelial and mesenchymal features. The data provide evidence that epithelial–mesenchymal transitions represent the basic principle of the tisuse heterogeneity in pleomorphic adenomas. Thus, pleomorphic adenomas demonstrate the potential of adult (neoplastic) epithelial cells to transdifferentiate into mesenchymal cells in vivo. Copyright © 1998 John Wiley & Sons, Ltd.     

Malignant myoepithelioma of the parotid gland: cytologic and histologic features

A case of malignant myoepithelioma of the parotid gland in a 34-year-old female is presented. In the fine-needle aspiration material, there was predominance of poorly cohesive polygonal cells with marked nuclear pleomorphism; no mitotic figures were observed. Focally, fragments of myxoid metachromatic intercellular material were also present. Histologically, the tumor was encepsulated, showing focal invasion of the capsule and tumor thrombi in the capsular vessels. The tumor was predominantly solid and myxoid, composed of cells with epithelioid features, marked anisonucleosis and a low mitotic activity. Immunohistochemically, the cells revealed positive staining for S-100 protein, vimentin, cytokeratins, glial acidic fibrillary protein and carcinoembryonic antigen; only several cell groups expressed smooth muscle actin and desmin; muscle specific actin was uniformly negative. In differential diagnosis, it was important to distinguish malignant myoepitelioma mainly from pleomorphic adenoma (mixed tumor), benign myoepithelioma, carcinoma ex pleomorphic adenoma and malignant melanoma. The criteria of malignancy in myoepithelial tumors are discussed.     

Intermediate filament expression in normal parotid glands and pleomorphic adenomas

Summary A comparative immunohistochemical study of intermediate filament expression in normal parotid glands and pleomorphic adenomas (PA) was performed using material fixed in a modified methacarn fixative. The normal myoepithelial cells of acini stained only with monoclonal antibodies 312C8-1 (cytokeratin (CK) 14) and 4.62 (CK 19) while myoepithelial/basal cells of ducts also reacted with antibodies 8.12 (CK 13, 16), 8.60 (CK 10, 11, +1), and PKK1 (CK 7, 8, 17, 18). Normal duct luminal cells showed a different CK profile, reacting consistently with ECK, a polyclonal antibody to epidermal prekeratin (CK 3,6), and monoclonal antibodies 4.62, PKK1 and 8.60. In PA, tumour cells at the periphery of ducts, in solid areas, and at the edge of myxoid regions all had CK profiles similar to normal myoepithelial/ basal cells except that antibody 4.62 was generally negative. Vimentin and glial fibrillary acidic protein (GFAP) were uniformly negative in normal parotids but showed variable (often strong) reactivity with some cells in chondroid, myxoid and solid areas of PA. A surprising feature of most PA was the variability of CK subtype expression not only from one case to another but also within morphologically similar areas of the same specimen. These results suggest that the morphology of PA is the result of diversity of tumour cell differentiation rather than the processes implicit in a reserve cell histogenetic model.     

Spontaneous infarction of a pleomorphic adenoma in parotid gland: diagnostic problems and review

Although infarction of parotid gland pleomorphic adenoma (PA) following fine-needle aspiration (FNA) has been well-documented, spontaneous infarction of PA has remained as an uncommon entity in the literature. To our knowledge, we report the second case of spontaneous infarction occurring in a parotid gland PA. A 44-yr-old man presented with a 2-yr history of slowly enlarging right parotid mass, which had become painful 1 mo before performing FNA biopsy. Smears revealed abundant necrotic debris, atypical squamous cells, and small cells with dark nuclei suggestive of a carcinoma. Histologic examination of the tissue fragments demonstrated degenerated clusters of cells and chondromyxoid matrix. The parotidectomy specimen had features consistent with those of an infarcted PA. Although appears to be rare, spontaneous infarction of PA should be considered in the differential diagnosis, since necrosis may mimic carcinoma and cause misinterpretation of necrosis as an indication of malignancy, in an otherwise benign salivary gland neoplasm.     

Nodular fasciitis of parotid region: a pitfall in the diagnosis of pleomorphic adenomas on fine-needle aspiration cytology

Fine-needle aspiration cytology (FNAC) is routinely employed for the preoperative diagnosis of salivary gland lesions. Although most cases show morphologic features characteristic of specific entities, some lesions can be diagnostically challenging. We report two parotid aspirates, initially diagnosed as pleomorphic adenoma on FNA. The patients, a 33-yr-old white man, and a 24-yr-old white woman, presented with indurated lesions arising in the parotid gland region. The aspirates from both patients were markedly hypercellular. Smears showed a mixture of spindle cells with a well-demarcated cytoplasm showing occasional long cytoplasmic process; and cells with abundant cytoplasm with round to oval eccentric nuclei, giving the impression of plasmacytoid cells of pleomorphic adenoma. The nuclear chromatin was evenly distributed and finely granular with one or two occasional small nucleoli. Intermingled with the tumor cells were scattered neutrophils, eosinophils, and macrophages. Aggregates of spindle cells were also seen embedded in a mucoid background with occasional small tufts of a fibrillar mucoid stroma. These fibrillar tufts were magenta red in the Diff-Quik stain, giving the impression of matrix of pleomorphic adenoma. Both cases were later diagnosed on histologic examination as nodular fasciitis. Nodular fasciitis should be considered in the differential diagnosis of a mass arising in association with the parotid gland.     

Diversity of collagen expression in the pleomorphic adenoma of the parotid gland

Summary The high diversity of collagen expression and its qualitative and quantitative aspects are demonstrated in pleomorphic adenoma using electron microscopy and specific histochemical methods. Great variability was observed in the amount, distribution and characteristics of the collagen found in the various types of tissue normally present in this tumour. Both deficient polymerization and hyperpolymerization of collagen and the occurence of desmoplasia were observed. Evidence is presented to suggest a role for localized collagenolysis in the invasiveness of this neoplasia.     

Melanoma in a carcinoma ex pleomorphic adenoma of the parotid gland: a case report and putative histogenesis

A rare example of melanoma arising in carcinoma ex pleomorphic adenoma is presented. The diagnosis, differential diagnosis, and putative histogenesis of the melanoma component are discussed.     

Simultaneous bilateral pleomorphic adenomas of the parotid glands with unilateral tyrosine rich crystalloids.

A case of simultaneous, bilateral pleomorphic adenoma of the parotid glands following irradiation to the head and neck for childhood Hodgkin's disease is presented. The tumour on the side given the highest radiation exposure contained so-called tyrosine rich crystalloids (TRCs). Simultaneous salivary gland neoplasms are rare; TRCs are also an unusual finding. Simultaneous pleomorphic adenomas with TRCs confined to one tumour have never been described, and any association between TRCs and irradiation has never been commented on. The precise nature of the TRCs remains obscure. Their unilateral distribution in this case supports the hypothesis that local factors are more important in their formation than systemic factors. In conjunction with other published work, this provides circumstantial evidence that irradiation may predispose to TRC deposition.