Establishment and characterization of METON myoepithelioma cell line derived from human palatal myoepithelioma: apical reference to the diverse differentiation potential.

Myoepithelioma is an extremely rare condition that accounts for 1-1.5 % of salivary gland tumors. It was formerly regarded as a subtype of pleomorphic adenoma, in which myoepithelial structural components predominated, but was listed as a separate disease entity in the 1991 World Health Organization classification (Seifert in Histological typing of salivary gland tumours. Springer, Berlin, 1991). Its histology is highly varied and recurrence is frequent (El-Naggar et al. in J Larygol Otol 103:1192-1197, 1989), with cases of malignant transformation having been reported (Seifert in Histological typing of salivary gland tumours. Springer, Berlin, 1991; Barnes et al. in Pathology and Genetics of head and neck tumours. IARC Press, Lyon, 2005), making this a difficult tumor to control in many cases. This is thought to be due to the multiple differentiation potential of myoepithelial cells, but the details are unknown. There have been a number of reports of the establishment of cell lines (Shirasuna et al. Cancer. 45:297-305, 1980; Jaeger et al. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 84:663-667, 1997), but numerous points remain unclear. We established a myoepithelial cell line designated METON, and investigated its characteristics. METON consists of cells with two different morphologies: spindle-shaped cells and epithelial-like cells. Then. we also used single-cell cloning method to establish various subclones (epithelial-like, spindle-like, and mixed epithelial-like/spindle-like cell lines). Among these, pluripotency markers were expressed by the mixed epithelial-like/spindle-like cell lines. The newly established cell line expressing these pluripotency markers will be extremely useful for elucidating the diverse histologies of salivary gland tumors.

Ultrastructural changes of the palatal mucosa following application of 4-nitroquinoline-l-oxide (4NQO) in rats subjected to major salivary gland excision.

OBJECTIVE: It has been suggested that saliva exerts a protective role against the carcinogenic effect of various substances in the oral cavity. The objective of this study was to examine the ultrastructural changes of the palatal mucosa caused by the application of 4-nitroquinoline-l-oxide (4NQO) in the presence or absence of saliva. STUDY DESIGN: Wistar-Furth rats subjected and not subjected to total bilateral excision of the major salivary glands were either painted with an aqueous solution of 4NQO or with propylene glycol only (controls). Two animals of each group were humanely killed periodically. The areas of the palatal lesions were immediately sliced and processed for TEM examination. RESULTS: Ultrastructurally, the progressive changes to squamous cell carcinoma were observed in the animals painted with 4NQO. In the desalivated animals group, the ultrastructural alterations appeared earlier than in the group with salivary glands. CONCLUSIONS: Saliva appeared to delay but not hinder tumor induction by 4NQO.

[A palate tumor revealed by pain]. / Une tumeur du palais révélée par des douleurs.

A 41-year-old female presented in April 1996 with a tumor of the hard palate revealed by increasing left palate pain. Adenoid cystic carcinoma was suspected on clinical and imaging data. Two limited surgical procedures showed a tumor histologically made of small lobules of granular cells, PAS positive and expressing S100 protein, infiltrating some medullary spaces of the palatine bone, consistent with a granular-cell tumour. Pain recurred in the territory of the maxillary branch of the left trigeminal nerve (V2). Imaging showed a tumor of the origin of V2-extending through the foramen rotondum. Two radical interventions in September and in October 2000 showed an infiltrating tumor of the V2 and palatine mucosa, with the same histology. There was no immuno-staining for p53, and less than 5% of nuclei expressed Ki67. Malignant Abrikossof tumors are exceptional, morphologically difficult to differentiate from benign ones, only metastasis proving malignancy. Tumor size above 5 cm, recurrence and infiltrative character are considered pejorative. The value of p53 and Ki67 expression remains controversial. We discuss our observation according to these criteria.

[Tyrosine-rich crystalloids in a myoepithelioma of the minor salivary glands in the smooth palate]. / Tyrosinreiche Kristalloide in Einem Myoepitheliom der kleinen Speicheldrüsen des Gaumens.

Tyrosine-rich crystalloids in tumors of the salivary glands are rare and have been reported mainly in specimens from Black African patients. The pathogenesis of these structures is still unclear, but pathological secretion by neoplastic myoepithelial cells is supposed. Millon's staining and ultrastructural examinations are used for confirming the diagnosis. We present the case report of a 59-year-old woman with a myoepithelioma of the minor salivary glands in the smooth palate containing tyrosine-rich crystalloids as an example of this rare phenomenon.

Malignant plasmacytoid myoepithelioma of the palate: histological observations compared to benign predominant plasmacytoid myoepithelial cells in pleomorphic adenoma of the palate.

Predominant benign plasmacytoid myoepithelial cells in pleomorphic adenoma and malignant plasmacytoid myoepithelioma cells were investigated morphologically. The cells of both tumors were plasmacytoid in appearance and sheet-like. Immunohistochemically, they were positive for keratin, vimentin, and S-100 protein, and negative for alpha-smooth muscle actin. In the malignant cells, large nuclei with irregular nuclear membranes and distinct nucleoi and occasional intranuclear inclusions and nuclear grooves were seen. Ultrastructural findings showed that the benign cells were richer in intermediate filaments and had fewer mitochondria. The intranuclear inclusions and nuclear grooves of the malignant cells were caused by invagination of the irregular nuclear membranes. Taken in their entirety, the above light microscopical nuclear findings may be useful as an adjunct for distinguishing malignant from benign plasmacytoid neoplastic myoepithelial cells of the salivary gland.

Atypical palatal papillomatosis treated by excision and full-thickness grafting.

Papillary lesions of the oral cavity are extremely common, and inflammatory palatal hyperplasia is well known to dental practitioners. Advanced sophistication in viral laboratory technologies makes it apparent that various forms of the human papilloma virus are often causative. However, this is not true for inflammatory palatal hyperplasia. This article describes a patient with anatomically well-demarcated, multiple squamous cell papillomas of the palate that could not be classified as inflammatory palatal hyperplasia, nor could a viral etiology be ascertained, despite exhaustive laboratory studies. The lesion recurred despite numerous surgical ablation attempts. Eradication was achieved only after applying free soft-tissue grafts over the areas of excision. The differential diagnosis of papillary lesions with an emphasis on viral etiology, laboratory studies associated with their identification, and a hypothesis that explains why grafting was the only successful means of treatment are also discussed.

Merkel cell carcinoma of palatal mucosa in a young adult: immunohistochemical and ultrastructural features.

The first case report of a merkel cell carcinoma arising from the palatal mucosa in a young adult is presented. The histopathological similarities of this tumour in skin and oral mucosa are also discussed. The patient was a 14-year-old female with a non-symptomatic painful swelling in the left molar region of the maxilla. Under the diagnosis of a malignant tumour, a partial maxillary resection was performed, but there was a recurrence, and finally the patient died of cerebral metastasis. The tumor was composed mainly of uniform small cells. Immunohistologically, a large number of the cells were reactive to neuron specific enolase (NSE) and cytokeratin CK19, and some of the cells were positive to CK8, CK13, CK20, PGP9.5 and CEA focally and slightly. Pseudo-rosette formation and squamous differentiation were frequently detected. The ultrastructure of the tumour cells showed abundant Golgi bodies associated with neurosecretory granules. We conclude that it is the first case of a Merkel cell tumour arising from palatal mucosa and invading underlying bone with reactive hyperplasia. These findings closely resemble those of the same tumour occurring in the skin

Lymphosarcoma with plasmacytoid differentiation in a scarlet macaw (Ara macao).

A lymphosarcoma in a scarlet macaw (Ara macao) affecting periocular structures is described. Microscopically and ultrastructurally, many of the lymphoid cells had plasmacytoid features. Polymerase chain reaction amplification failed to detect exogenous avian retrovirus RAV-1 in the neoplastic mass.

Correlation of light microscopic, immunocytochemical and ultrastructural cytomorphology of anaplastic large cell Ki-1 lymphoma, an activated lymphocyte phenotype. A case report.

BACKGROUND: Anaplastic large cell Ki-1 lymphoma has been proposed to be a neoplasm of activated lymphocytes, mostly of T-cell origin. CASE: A previously healthy 12-year-old boy presented with a two-month history of a rapidly growing hard palate mass that involved the nasal cartilage and extended to the floor of the right orbit. By light microscopy (LM) the aspirates were very cellular, containing single, pleomorphic cells and occasional cellular aggregates. The cells showed distinct polarity, with the large, anaplastic nucleus at one end and the tapering cytoplasm, including a prominent paranuclear halo (or "hof"), at the other end ("hand mirror" appearance). The cytoplasmic border showed prominent ruffling, concentrated at the two poles of the cells and corresponding to the areas of the protopod and uropod. Immunocytochemically (ICC) the cells were positive for Ki-1, epithelial membrane antigen and UCHL-1, all of which showed both membrane positivity along with Golgi area staining. LCA showed variable membrane staining. Ultrastructurally (electron microscopy [EM]) the polarity was recapitulated, with an eccentric, horseshoe-shaped nucleus partially enclosing a prominent Golgi complex with associated centrosomes and asymmetric plasma membrane ruffling. CONCLUSION: All three levels of examination (LM, ICC and EM) revealed tumor cell features corresponding to the phenotype of the activated lymphocyte. These features are characteristic, thus allowing the diagnosis of Ki-1 anaplastic lymphoma by fine needle aspiration cytology.

Myoepithelial carcinoma arising in a benign myoepithelioma: immunohistochemical, ultrastructural, and flow-cytometrical study.

A case of myoepithelial carcinoma arising in a benign myoepithelioma of the minor salivary gland in a 71-year-old patient is reported. The tumor presented initially on the palate and had been diagnosed as "benign lesion" 40 years before. It recurred 22, 36, and 40 years after initial presentation, and a similar histopathological diagnosis was rendered. One year after the last recurrence, the tumor recurred showing typical changes of malignant transformation, and the diagnosis was malignant myoepithelioma. The light microscopy and ultrastructural features of the initial tumor were typical of plasmocytoid myoepithelioma. There were abundant round cells and rare spindle cells with uniform dispersed filaments, sometimes arranged in parallel streams without evidence of dense bodies. These cells showed micropinocytotic vesicles along the cell membrane with poorly developed intercellular junctions and were surrounded by a basal membrane. The malignant counterpart showed fewer plasmocytoid cells and a rather epithelial pattern with marked nuclear pleomorphism and formation of small, or rarely large, glandular lumina. The immunohistochemical features were similar for the benign and malignant tumors, with positivity for S-100 protein, vimentin, cytokeratins, and CAM 5.2, and were negative for GFAP, muscle-specific actin, CEA, and desmin. Flow cytometry showed a change in the DNA content profile. The benign myoepithelioma had a diploid DNA content with a low S-phase fraction of 3.9% and proliferative index of 9.1%, while the myoepithelial carcinoma had an evident aneuploid DNA stem line and an increased S-phase fraction of 8.3% with a proliferative index of 18.1%.

Rhabdomyosarcoma of the oral cavity. Report of four cases.

Clinical and pathologic findings of four cases of rhabdomyosarcoma of the oral soft tissues are described that include findings from immunohistochemistry and electron microscopy. Three cases occurred in children under 16 years of age and one in a 22-year-old. Included is a brief discussion on reported gene abnormalities that may contribute to neoplastic development.

Follicular dendritic cell tumors of the oral cavity.

Follicular dendritic cell tumors are uncommon, and all the reported cases have occurred as primary lymph node tumors. We report two cases in the oral cavity, one in the soft palate and one in the tonsil. The tumors were characterized by sheets, whorls, and storiform arrays of spindly and syncytial-appearing cells with oval nuclei, fine chromatin, distinct nucleoli, and occasional nuclear pseudoinclusions. Multinucleated forms were present and were prominent in one case. An unusual feature was the presence of irregular pseudovascular spaces, which could raise a concern for vascular neoplasm. Because the tumors showed cohesive growth and a sharp interface with the fibrous stroma, they could also be mistaken for carcinoma, sarcoma, or melanoma. After radiation therapy, the palatal tumor showed a greater degree of nuclear pleomorphism, numerous nuclear pseudoinclusions, and striking nuclear grooving and foldings, mimicking interdigitating reticulum cell tumors. The diagnosis in both cases was confirmed by immunoreactivity with CD21 and CD35 and by ultrastructural demonstration of interdigitating cell processes with desmosomes. Both tumors also showed unexpected immunoreactivity with muscle-specific actin. Follicular dendritic cell tumor merits wider recognition of its possible extranodal occurrence as well as its full morphological spectrum in order to better define its behavior.

Recurrent parapharyngeal rhabdomyoma. Evidence of neoplastic nature of the tumor from cytogenetic study.

A 64-year-old Caucasian male with a left parapharyngeal mass had a past medical history that was significant for excision of a benign rhabdomyoma of the soft palate 30 years previously. Then 25 years ago, the tumor recurred in the palate and retropharyngeal space on the left and was reexcised. Histologic examination of all three excisions showed adult rhabdomyoma. Ultrastructural and histochemical studies of the second excision of this tumor have been published previously. The present study included histologic, ultrastructural, immunohistochemical, and cytogenetic analyses. The histologic and ultrastructural features of the tumor were identical to those reported 25 years ago. Immunohistochemical studies demonstrated that the tumor cells were desmin and myoglobin positive and vimentin negative. Focal positivity for CD56 was also present. Intracellular inclusions in the tumor cells were strongly positive for desmin. Cytogenetic examination of short-term cultures of the tumor cells demonstrated clonal chromosome abnormalities in 60% of metaphases. The majority of cells showed a reciprocal translocation between chromosomes 15 and 17 as the sole abnormality. A minor clone was characterized by abnormalities of the long arm of chromosome 10. The presence of clonal structural chromosome abnormalities in extracardiac adult rhabdomyoma lends strong support to the idea that these rare tumors are true neoplasms rather than hamartomatous or regenerative lesions.

[Ultrastructural and histochemical study of a pleomorphic adenoma of the palate]. / Hypermikroskopike kai histochemike melete polymorphou adenomatos tes hyperoas.

Histochemical and ultrastructural study of the epithelial regions forming lumina in one case of pleomorphic adenoma of the palate was undertaken. The ultrastructural findings suggest that these epithelial regions are derived from the intercalated ducts. The presence in the cytoplasm of periluminal cells of pinocytotic vesicles and vacuoles containing material similar in appearance of that seen in the luminal supports a reabsorptive activity of these cells. The microcalculi of calcium phosphate occasionally seen in the cytoplasm of these cells may be formed by the phagocytosis of the endocytotic material from the lumina.

Spitz nevus of the palate. Report of a case.

A 4-year-old Japanese girl with a nonpigmented nodule on the anterior portion of the palate since birth is described. The overall microscopic appearance of the lesion was very similar to that of Spitz nevus of the skin. Diagnosis of Spitz nevus (mixed epithelioid cell and spindle cell nevus) was made on the basis of the clinical and histologic criteria for differentiating this lesion from malignant melanomas and common compound nevi. Positive immunostaining of epithelioid and spindle cells for S-100 protein and neuron-specific enolase was also indicative of their nevocellular nature. Review of the cases of Spitz nevus from the literature revealed that the present case most probably represents the first reported instance of this type of nevus in the oral cavity.

Desmoplastic amelanotic melanoma of palate: a case report with immunohistochemistry and electron microscopic studies.

A 24 year-old male with painful swelling over the right side of his palate for about two weeks was presented. An incisional biopsy was performed. In a routine hematoxylin and eosin examination by light microscopy, spindle and epithelioid cells with a bizarre appearance were discernible in the submucosal area. A pagetoid pattern was found in areas of the epithelium. Since this is not a remarkable finding, further examinations, such as the Trichrome-Masson and silver stain, immunohistochemistry using cytokeratin, vimentin, S-100, leukocyte common antigen, factor VIII, and alpha-1-antichymotrypsin detection kits, and electron microscopy were all carried out. According to the histological pattern of cells and the positive findings from the special stains, immunohistochemistry, and electron microscopy, a diagnosis of desmoplastic amelanotic melanoma was made. This variant of melanoma is a rare disorder with unremarkable, non-specific clinical manifestations in the oral cavity, which makes the diagnosis of this disease more difficult. We, therefore, report one case of this disease. Owing to the fact that diagnosis of this variant was mainly based on the positive findings of vimentin and S-100 in the immunohistochemistry examination and intracellular premelanosome detected by electron microscopy, immunodiagnosis and electron microscopy seem to be essential for differential diagnosis.

Polymorphous low-grade adenocarcinoma of the palate: report of a case with electron microscopy.

A case of polymorphous, low-grade adenocarcinoma of the palate is presented with special emphasis on the histologic and ultrastructural features of this recently described entity.

Embryonal rhabdomyosarcoma.

Rhabdomyosarcoma is one of the most common malignancies of the mesenchymal tissue in the head and neck region. A case of a 26-year-old male with oral rhabdomyosarcoma is presented. The clinical and pathologic aspects of this malignancy are also reviewed. Furthermore, the histopathologic and ultrastructural features of this neoplasia are described and the important role of electron microscopy in diagnosis of the myogenic tumor is emphasized. Finally, different modes of treatment for the rhabdomyosarcoma are discussed.