Mutations associated with carcinomas arising from pleomorphic adenomas of the salivary glands

Evaluation of a subset of tumor suppressor gene for copy number and epigenitic changes in pleomorphic adenoma and carcinoma ex-pleomorphic adenoma carcinogenesis

OBJECTIVE

The progression of pleomorphic adenoma (PA) to carcinoma ex-pleomorphic adenoma (CXPA) encompasses several genomic alterations involving complex pathways. Tumor suppressor genes seem to play important roles in the tumorigenesis of both tumors. The aim of this study was to evaluate copy number and methylation of tumor suppressor genes' status in PA and CXPA samples.

STUDY DESIGN

Eight cases of PA, 2 cases of residual PA in CXPA, and 5 cases of CXPA were studied; the latter were classified according to invasiveness and histopathological subtype. Changes in 41 tumor suppressor genes were evaluated by multiplex ligation-probe dependent amplification analysis.

RESULTS

Copy number losses of CASP8, MLH1, and RARB genes were associated with PA and CXPA, while KLK3 and AI69125 copy number losses were exclusive to CXPA. The sarcomatoid carcinoma showed more copy number alterations compared with other subtypes. Hypermethylation of RASSF1 was found mainly in PA and less frequently in malignant tumors.

CONCLUSIONS

CASP8, MLH1, and RARB tumor suppressor genes were altered by copy number losses during PA progression to CXPA. Lastly, RASSF1 inactivation by methylation was also detected in both tumors.

The landscape of gene fusions and somatic mutations in salivary gland neoplasms - Implications for diagnosis and therapy

Recent studies of the genomic landscape of salivary gland tumors have provided important insights into the molecular pathogenesis of these tumors. The most consistent alterations identified include a translocation-generated gene fusion network involving transcription factors, transcriptional coactivators, tyrosine kinase receptors, and other kinases. In addition, next-generation sequencing studies of a few subtypes of salivary neoplasms have revealed hotspot mutations in individual genes and mutations clustering to specific pathways frequently altered in cancer. Although limited, these studies have opened up new avenues for improved classification and targeted therapies of salivary gland cancers. In this review, we summarize the latest developments in this field, focusing on tumor types for which clinically important molecular data are available.

Assessment of TP53 mutations in benign and malignant salivary gland neoplasms

Despite advances in the understanding of the pathogenesis of salivary gland neoplasms (SGN), the molecular pathways associated with enhanced tumor growth and cell survival remain to be established. The aim of the present study was to investigate whether TP53 mutations are relevant to SGN pathogenesis and if they impact on p53 protein expression. The study included 18 benign and 18 malignant SGN samples. Two polymorphic microsatellite markers at the TP53 genetic locus were chosen to assess loss of heterozygosity (LOH) in the samples that had matched normal DNA. The TP53 exons 2-11 were amplified by PCR, and all of the products were sequenced. Reverse transcription-PCR of the TP53 open reading frame (ORF) was carried out in the samples that had fresh tissue available, and immunohistochemistry for the p53 protein was performed in all samples. TP53 LOH was only found in two pleomorphic adenomas. We found two missense mutations in exon 7 (one in a pleomorphic adenoma and the other in a polymorphous low grade adenocarcinoma), another in exon 8 (in a carcinoma ex pleomorphic adenoma) and a fourth missense mutation in exon 10 (in a mucoepidermoid carcinoma). In addition, a nonsense mutation was found in exon 8 of an adenoid cystic carcinoma. Several intronic and exonic SNPs were detected. Although almost all of the malignant samples were immunopositive for p53, approximately 37% of the benign samples were positive, including the sample harboring the missense mutation and one of the samples that showed LOH. The complete TP53 ORF could be amplified in all samples analyzed, including the IHC negative samples, the samples showing LOH and one sample displaying a missense mutation. In summary, our results show that TP53 mutations are not a frequent event in SGN and that p53 immunopositivity might not be associated with sequence mutations in SGN.

Immunohistochemical Expression of p53 in Pleomorphic Adenoma and Carcinoma Ex Pleomorphic Adenoma

Context. Immunohistochemical stains for p53 are used as a diagnostic marker associated with malignancy in several histologic types of salivary gland tumors. This marker may be useful in differentiating pleomorphic adenoma (PA) from carcinoma ex pleomorphic adenoma (CPA), as these tumors are often difficult to distinguish on the basis of morphology alone. Objective. to evaluate whatever inactivation of tumor suppressor gene (p53) increases with the tumor progression from normal salivary tissue to PA and eventually CPA. Design. Paraffin blocks of 29 cases of PA, which were surrounded by normal parotid gland, and 27 cases of carcinoma ex pleomorphic adenoma were retrieved and validated. In all cases of carcinoma ex pleomorphic adenoma, a PA “ghost” was identified, and the malignant element was either undifferentiated carcinoma or adenocarcinoma. Results. The results showed negative nuclear expression of P53 in normal parotid gland. Nuclear P53 was expressed strongly in 6/29 (20.7%) pleomorphic salivary adenoma and 10/27 (37%) carcinoma ex pleomorphic adenoma. Conclusion. Our data suggest that inactivation of p53 may play an important role in the evolution of pleomorphic salivary adenoma and carcinoma ex pleomorphic adenoma.

Transformation of pleomorphic adenoma to carcinoma ex pleomorphic adenoma of the parotid gland is independent of p53 mutations

BACKGROUND AND OBJECTIVES

This retrospective study was performed to evaluate the status of p53 in pleomorphic adenomas and carcinomas ex pleomorphic adenoma in the parotid gland. As loss or mutation of p53 can cause malignant transformation, the possible degeneration of pleomorphic adenomas to carcinomas ex pleomorhic adenoma was investigated by mutational analysis.

METHODS

Twenty-five Patients including 14 patients with pleomorphic adenomas and 11 patients with carcinoma ex pleomorphic adenoma of the parotid gland were examined for p53 status. DNA was extracted out of paraffin-embedded tissue and PCR was performed for the coding exons 2-11. Denaturing gradient gel electrophoresis (DGGE) was carried out for mutational analysis and DNA sequencing was performed in case of a suspected mutation.

RESULTS

Fourteen pleomorphic adenomas and 11 carcinomas ex pleomorphic adenoma were screened for p53 status and potent mutations. Subsequent sequencing of the distinct exons showed no mutation.

CONCLUSION

We could not detect mutations of p53 neither in benign nor malignant parotid tumors and we therefore assume that p53 plays no role in the transformation from pleomorphic adenoma to carcinoma ex pleomorphic adenoma.

Satellite tumors surrounding primary pleomorphic adenomas of the parotid gland

The occasional local recurrence of benign pleomorphic adenoma (PA) has generally been attributed to the vulnerability of the tumor capsule. Although some reports have also noted the presence of satellite tumors associated with PA recurrence, only few reports have focused on this issue. We paid special attention to the satellite lesions apart from the main tumors and discussed their frequency, origin, nature and the ways of treating them. A total of 108 specimens of primary parotid gland PA resected at the Okayama Saiseikai General Hospital from 1988 to 2008 were microscopically reviewed. Four (3.7%) patients displayed a main mass with satellite tumors in a single parotid gland. The immunohistochemical analysis of p53 and Ki-67 index showed no distinct difference between PAs with satellite tumors and those without. Satellite tumors surrounding the main mass of parotid PA is relatively rare. In most cases, such satellite tumors will arise from capsular perforation of the primary tumor cells. Preoperative evaluation to recognize the existence of satellite tumors would be important and capsular dissection should be discouraged. We could not find any evidence suggesting that primary PA with satellite tumors could be more biologically aggressive than those without.

Overexpression of cyclooxygenase-2 correlates with cytoplasmic HuR expression in salivary mucoepidermoid carcinoma but not in pleomorphic adenoma

BACKGROUND

The overexpression of cyclooxygenase (COX)-2 in several human carcinomas suggests that COX-2 is related to carcinogenesis. Although COX-2 expression has been shown to be up-regulated in carcinomas of the salivary gland, its mechanisms are not completely understood. HuR is an mRNA-binding protein that controls the stability of certain transcripts including COX-2.

METHODS

The expression of COX-2 and HuR was determined by immunohistochemistry in 28 cases of salivary pleomorphic adenoma and 18 cases of salivary mucoepidermoid carcinoma.

RESULTS

28.6% and 72.2% of the pleomorphic adenomas and mucoepidermoid carcinomas showed high COX-2 expression respectively. 35.7% of pleomorphic adenomas and 72.2% of mucoepidermoid carcinomas were tested positive for HuR in the cytoplasm of tumor cells. There was a correlation between a high COX-2 immunoreactivity and cytoplasmic HuR expression in mucoepidermoid carcinomas but not in pleomorphic adenomas.

CONCLUSION

This study suggests that cytoplasmic HuR is correlated with COX-2 expression in salivary mucoepidermoid carcinomas. In addition, the immunoreactivity of COX-2 and cytoplasmic HuR might be used to evaluate the nature of a borderline malignancy in the salivary glands.

Loss of heterozygosity occurs predominantly, but not exclusively, in the epithelial compartment of pleomorphic adenoma

Pleomorphic adenoma (PA), being the most common benign tumor of the salivary glands, is composed of epithelial and mesenchymal compartments. In this study, we analyzed 19 microsatellite markers from chromosomal arms 6q, 8q, 9p, 12q, and 17p in 31 PAs and 3 carcinoma ex pleomorphic adenomas (CXPAs) as well as 11 other non-PA-related carcinomas of the salivary gland for comparison. In our analysis, we differentiated between epithelial and mesenchymal tissues. Loss of heterozygosity (LOH) in PAs was most often found in 8q (32%) and 12q (29%). Two of the three CXPAs displayed allelic loss at all chromosomal arms investigated, whereas the results of the non-PA-related carcinomas were rather heterogeneous. LOH could not only be detected in the epithelial, but also in the mesenchymal, compartments of a subset of PAs, especially at chromosomal arm 8q. Concerning the CXPAs, we were able to demonstrate allelic losses not only in the malignant epithelial compartment, but also in the residual adenoma parts. Our data give further evidence that alterations in 8q may be an early event in PA tumorigenesis, whereas LOH in 12q may characterize cells with the potential to transform in CXPAs.

TP53 mutations in salivary gland neoplasms

Many studies have demonstrated that loss of TP53 gene function has an important role in the genesis of many neoplasms, including salivary gland neoplasms. The purpose of this study was to examine the mutation profile of the TP53 gene in salivary gland neoplasms. Genomic DNA was extracted from paraffin-embedded tissues of pleomorphic adenoma, carcinoma in pleomorphic adenoma, mucoepidermoid carcinoma, adenoid cystic carcinoma and polymorphous low grade adenocarcinoma. Exons 5 to 8 of the TP53 gene were amplified by polymerase chain reaction (PCR) to perform single-stranded conformational polymorphism (SSCP) analysis. Band shifting was observed in exons 5, 6 and 8 in 9 out of 18 neoplasms. The results of this study suggest that mutations in TP53 gene are related to salivary gland neoplasms pathogenesis and that exons 5 and 8 are most frequently involved.

Expression of cell cycle-regulated proteins pRB2/p130, p107, E2F4, p27, and pCNA in salivary gland tumors: prognostic and diagnostic implications

The retinoblastoma family consists of the tumor suppressor nuclear phosphoprotein pRb/p105 and related proteins p107 and pRb2/p130. Recent immunohistochemical studies of the retinoblastoma family of proteins in lung and endometrial cancer and choroidal melanomas show a tight inverse correlation between the histologic grading in the most aggressive tumor types and pRb2/p130 expression. This led us to investigate the role of pRb2/p130 in salivary tumors. We studied the expression of pRb2/p130, p107, E2F4, p27, and PcNA by immunohistochemistry in a panel of 44 salivary gland tumors. We found a direct correlation between the cytoplasmic expression of pRb2/p130 and tumor grading and the presence of metastasis that was highly statistically significant (P < 0.001). Additionally, increased cytoplasmic pRb2/p130 expression was significantly correlated with a decreased probability of survival (P < 0.001). Interestingly, p107 nuclear expression showed a strong direct correlation when compared with the same variables. pRb2/p130 showed the highest percentage of undetectable nuclear levels in the specimens examined and the tightest inverse correlation (P < 0.0001) with both the histologic grading and pCNA expression in malignant salivary tumors. Additionally, E2F4 showed an identical localization pattern as to that of pRb2/p130. These data suggests an important role for pRb2/p130 in the pathogenesis and progression of certain salivary gland cancers.

Precancerous foci in pleomorphic adenoma of the salivary gland: recognition of focal carcinoma and atypical tumor cells by P53 immunohistochemistry

BACKGROUND

It is still controversial if atypical tumor cells scattered in salivary pleomorphic adenomas are precancerous and how carcinoma arises in pleomorphic adenomas.

METHODS

We studied clinicopathologically the frequency and variation of cellular atypia among tumor cells and examined the expression status of p53 gene products as well as proliferating cell nuclear antigen (PCNA) in 101 surgical materials of pleomorphic adenomas.

RESULTS

Histopathologically, atypical tumor cells were found in 51% of the cases examined. Their mode of distribution was classified into three groups: focal (six cases, 6%) which could be identified as focal carcinoma, measuring less than 1 mm in diameter; sporadic (15 cases, 15%) and singular (30 cases, 30%). These atypical cells were located mainly within sheet-like nests of tumor cells but not in chondroid or fibro-hyaline foci. Immunohistochemically, most of the atypical cells were positive for p53 gene products and PCNA.

CONCLUSION

The results indicated that atypical cells with p53 protein accumulation in their nuclei could be regarded as cells in a precancerous state not yet forming an apparent carcinomatous nest. Some cell population with these atypical cells are likely to form focal carcinomas and then to an apparent form of carcinoma in pleomorphic adenoma.

DNA copy number changes in carcinoma in pleomorphic adenoma of the salivary gland: a comparative genomic hybridization study

Pleomorphic adenoma is the most common benign tumor of the salivary glands and is rarely associated with concurrent epithelial malignancy, which is designated as carcinoma in pleomorphic adenoma (CPA). Genetic abnormalities potentially related to the development of CPA have not been fully investigated. We analyzed DNA copy number changes in each of the adenomatous and carcinomatous components of seven CPA by comparative genomic hybridization using DNA extracted from microdissected tissues of formalin-fixed, paraffin-embedded tumor samples. Carcinomatous components of CPA showed multiple DNA copy number changes at 1-18 different genomic sites (mean 13 sites). Adenomatous components displayed less frequent DNA copy number changes (0-13 sites; mean, 5). In both components, the majority of the changes were gains. The most common recurrent gains in carcinomatous components were seen at 6q (four cases in each), whereas gains at 13q1-2 and 15q1 were most frequently detected in adenomatous components (three cases in each). In five CPA, the same chromosomal regions were involved in the DNA copy number changes detected in both components. Our data suggest that an accumulated or increased number of chromosomal changes including 6q abnormalities may be associated with the development of carcinomatous components in a subset of CPA.

Increase in immune cell infiltration with progression of oral epithelium from hyperkeratosis to dysplasia and carcinoma

In the present study, epithelium derived lesions of various pathological manifestations were examined histologically and immunohistochemically for mononuclear cell infiltration. The infiltrate under the transformed epithelium of oral lesions, was examined for differences in the composition of immune mononuclear cells as the epithelium moves from hyperkeratosis through various degrees of dysplasia to squamous cell carcinoma. The study was performed on 53 human tongue tissues diagnosed as hyperkeratosis (11 cases), mild dysplasia (nine cases), moderate and severe dysplasia (14 cases) and squamous cell carcinoma (19 cases). A similar analysis was performed on 30 parotid gland tissues diagnosed as pleomorphic adenoma (14 cases) and carcinoma ex-pleomorphic adenoma (16 cases). Immunohistochemical analysis of various surface markers of the tumour infiltrating immune cells was performed and correlated with the transformation level as defined by morphology and the expression of p53 in the epithelium. The results revealed that, in the tongue lesions, the changes in the epithelium from normal appearance to transformed were accompanied by a corresponding increase in the infiltration of CD4, CD8, CD14, CD19+20, and HLA/DR positive cells. The most significant change was an increase in B lymphocytes in tongue lesions, that was in accordance with the transformation level (P<0.001). In the salivary gland, a significant number of cases did not show an infiltrate. In cases where an infiltrate was present, a similar pattern was observed and the more malignant tissues exhibited a higher degree of immune cell infiltration.

A case of myoepithelial carcinoma displaying biallelic inactivation of the tumour suppressor gene APC in a patient with familial adenomatous polyposis

Familial adenomatous polyposis (FAP) is an autosomal dominant disorder caused by mutation of the APC gene. It is characterised by the appearance of hundreds to thousands of colorectal adenomas in adolescence and the subsequent development of colorectal cancer. Various extracolonic malignancies are associated with FAP, including desmoids and neoplasms of the stomach, duodenum, pancreas, liver, and brain. We present a family affected by FAP with an exon 14 APC mutation displaying two rare extracolonic lesions, a hepatoblastoma and a myoepithelial carcinoma. The hepatoblastoma was found in a male patient aged 2 years. The second lesion, a myoepithelial carcinoma of the right cheek, was found in a female patient aged 14 years. Inactivation of the normal APC allele was demonstrated in this lesion by loss of heterozygosity analysis, thus implicating APC in the initiation or progression of this neoplasm. This is the first reported case of this lesion in a family affected by FAP.

Dedifferentiation of adenoid cystic carcinoma: report of a case implicating p53 gene mutation

Adenoid cystic carcinoma is an indolent tumour with an unfavorable long-term prognosis. Dedifferentiation of adenoid cystic carcinoma, which is associated with an accelerated clinical course, has recently been described. We report a case with immunohistochemical and molecular workup to elucidate the likely mechanism of dedifferentiation. The patient, a 64-year-old woman, developed dedifferentiated adenoid cystic carcinoma of the submandibular gland ab initio, accompanied by cervical lymph node metastasis. Histologically, the low-grade adenoid cystic carcinoma merged gradually into an extensive dedifferentiated component that was composed of solid sheets and cords of anaplastic tumor cells with focal gland formation. Immunohistochemically, the dedifferentiated component, but not the adenoid cyst carcinoma component, showed strong overexpression of p53 protein and cyclin D1, as well as a higher Ki67 index. Molecular study confirmed the presence of p53 gene mutation selectively in the dedifferentiated component, suggesting a pivotal role of p53 gene alteration in the dedifferentiation process of adenoid cystic carcinoma.

HIN-1, a putative cytokine highly expressed in normal but not cancerous mammary epithelial cells

To identify molecular alterations implicated in the initiating steps of breast tumorogenesis, we compared the gene expression profiles of normal and ductal carcinoma in situ (DCIS) mammary epithelial cells by using serial analysis of gene expression (SAGE). Through the pair-wise comparison of normal and DCIS SAGE libraries, we identified several differentially expressed genes. Here, we report the characterization of one of these genes, HIN-1 (high in normal-1). HIN-1 expression is significantly down regulated in 94% of human breast carcinomas and in 95% of preinvasive lesions, such as ductal and lobular carcinoma in situ. This decrease in HIN-1 expression is accompanied by hypermethylation of its promoter in the majority of breast cancer cell lines (>90%) and primary tumors (74%). HIN-1 is a putative cytokine with no significant homology to known proteins. Reintroduction of HIN-1 into breast cancer cells inhibits cell growth. These results indicate that HIN-1 is a candidate tumor suppressor gene that is inactivated at high frequency in the earliest stages of breast tumorogenesis.

Submandibular gland adenocarcinoma of intercalated duct origin in Smgb-Tag mice

A line of transgenic mice that develops submandibular gland adenocarcinoma of intercalated duct origin was established. In these mice, the oncogene SV40 T antigen (Tag) is expressed from the neonatal submandibular gland secretory protein b (Smgb) gene promoter. This hybrid gene directs expression of the oncoprotein to neonatal submandibular gland proacinar and terminal tubule cells and to intercalated ducts of the adult gland. Transgene expression resulted in duct luminal cell hyperplasia as early as 20 to 30 days postnatally, which progressed to dysplasia by 3 to 4 months of age. Marked dysplasia and in situ carcinoma were evident at 4 to 6 months of age. All histologic changes were more pronounced in males. Submandibular gland adenocarcinoma developed stochastically in more than half of the adult male mice by 12 months of age (average age: 10.8 months, range: 6 to 13.5 months). Tag expression persisted in in situ carcinoma and all tumors. Using a combination of immunocytochemical and ultrastructural criteria, submandibular gland dysplasia and tumors were found to originate from intercalated ducts. The dysplastic ducts and adenocarcinoma in Smgb-Tag mice were morphologically similar to previously reported Tag-induced dysplasias of striated ducts and granular convoluted tubules and a Tag-induced adenocarcinoma of striated duct origin. These findings demonstrate that salivary gland dysplasias and tumors of similar histologic appearance can arise from distinct differentiated cell types. Analysis of the molecular changes accompanying tumor formation in Smgb-Tag mice could increase knowledge of human salivary gland tumorigenesis.

ras gene mutations in salivary gland tumors

OBJECTIVE

To assess the prevalence of activating mutations in K-ras and H-ras genes in salivary gland tumors with ductal or acinar differentiation and to evaluate their potential correlation with clinical parameters.

DESIGN

Paraffin-embedded tissue samples of salivary gland carcinomas were investigated by the application of a direct sequence analysis procedure with automated DNA sequencing of polymerase chain reaction-amplified ras sequences.

SETTING

Tertiary care teaching hospital.

PATIENTS

Twenty-four patients with salivary gland carcinoma were surgically treated. Nine had adenocarcinoma, 1 had adenosquamous carcinoma, 11 had mucoepidermoid carcinoma, and 3 had acinic cell carcinoma.

RESULTS

Point mutations were detected in 7 (29%) of the 24 carcinomas examined. The K-ras gene was mutated in only 2 samples (8%): a GGC-to-ATC mutation at codon 13 in an adenocarcinoma and a GGC-to-GTC transversion mutation at codon 13 in a mucoepidermoid carcinoma. Five (21%) harbored H-ras mutations: 4 contained a GGC-to-GTC transversion mutation at codon 12 and 1 had 2 distinct mutations, the same G-to-T at codon 12 as was shown in the other cases and a GGT-to-GGA heterozygous mutation at codon 13. All the H-ras mutations were in the group of mucoepidermoid carcinoma lesions (45%; 5/11).

CONCLUSION

Our data suggest that K-ras gene alteration is probably not an important factor in the oncogenesis of human salivary gland tumors. However, mutational activation of the H-ras gene appears to play a role in the development and/or progression of salivary gland mucoepidermoid carcinomas.

H-ras gene mutations in salivary gland mucoepidermoid carcinomas

BACKGROUND

The authors' recent investigation of salivary gland tumors in ras gene alteration has suggested that K-ras activation may not play a role in their oncogenesis but H-ras may, especially in mucoepidermoid carcinomas. A study was undertaken to assess the overall incidence of mutated H-ras genes in mucoepidermoid carcinomas and to discover its potential correlation with clinicopathologic parameters.

METHODS

Fifty samples from patients with salivary gland mucoepidermoid carcinoma were analyzed for point mutations at codons 12, 13, and 61 of the H-ras gene using the polymerase chain reaction followed by automated direct sequencing methodology.

RESULTS

Mutated H-ras genes were detected in 9 patients, for an overall incidence of 18% (9 of 50 patients). All but 1 of the mutations occurred at codon 12: a GGC-to-GTC transversion in 8 patients and a GGC-to-GAC transition in 1 patient, resulting in the amino acid substitution of valine and aspartic acid, respectively, for glycine. One of the samples showed concurrent mutations at codons 12 (GGC-to-GTC) and 13 (GGT-to-GGA). None of the samples demonstrated mutations involving codon 61. The H-ras mutations were observed in 5% (1of 21), 17% (2 of 12), and 35% (6 of 17) of low, intermediate, and high grade lesions, respectively.

CONCLUSIONS

These data suggest involvement of H-ras activation in conjunction with other yet-unknown events in the development and/or progression of mucoepidermoid carcinomas. It is noteworthy that a stepwise increase in the frequency of H-ras mutations strongly correlates with tumor grade (P = 0.017). Molecular analysis of this gene alteration may provide assistance in the determination of tumor grade and differentiation.

Concurrent cytogenetic, interphase fluorescence in situ hybridization and DNA flow cytometric analyses of a carcinoma ex-pleomorphic adenoma of parotid gland

We report the cytogenetic, fluorescence in situ hybridization (FISH), and DNA ploidy analyses of a high grade carcinoma ex-pleomorphic adenoma of the submandibular gland. Our overall combined analyses showed a marked DNA aneuploidy and numerical abnormalities involving all chromosomes. Cytogenetic analysis revealed a near tetraploid modal chromosomal number with tetraploid loss of chromosomes Y, 1, 6, 9, 11, 14, 15, 17, and 19-21 and hypertetraploid gain of chromosomes 7, 8, and 22. The structural abnormalities included der(1;14)(q10;q10), del(6)(q15q34), +del(6)(q15q34), +der(8) t(1;8)(q12;q12.2),der(9;19)(q10;q10),add(14)(p11.2),i(20)(q10),der(21) t(8;21)(q11.2;q22.3),+der(21)t(8;21) (q11.2;q22.3). Interphase FISH of the primary and short-term cultured cells using directly labeled pericentromeric probes for chromosomes 6-12, 17, 18, and Y resulted in alterations corresponding to the cytogenetic findings. DNA ploidy analysis of both the primary and cultured tumor cells showed a hyperdiploid stemline with DNA indices of 2.6. The results indicate that: (1) marked numerical, structural chromosomal, and DNA content abnormalities are present in this tumor; and (2) alteration at 8q and 6q regions, together with previous results, suggest an association between these events and the development and/or progression of this tumor.

Myoepithelial carcinoma (malignant myoepithelioma) of the parotid gland arising in a pleomorphic adenoma

A myoepithelial carcinoma, a rare malignant salivary gland neoplasm, arose in a pleomorphic adenoma of the parotid gland. The initial tumour was a pleomorphic adenoma with epithelial and myoepithelial elements. Subsequently the tumour recurred twice and was characterised by invasion of the mandible. Histological examination of the second recurrence showed a malignant spindle cell neoplasm with an infiltrative growth pattern and a high mitotic rate. There was involvement of local lymph nodes. The immunophenotype was characteristic of myoepithelial differentiation: tumour cells stained positively with anticytokeratin antibodies, S-100 protein, alpha smooth muscle actin, and vimentin. Electron microscopy confirmed myoepithelial differentiation, with small foci of keratinocytic phenotype. Large numbers of tumour cell nuclei were reactive with the anti-p53 antibody, DO-7, in contrast to the two previous resections. Thus malignant transformation of a pleomorphic adenoma may involve myoepithelial as well as epithelial elements. Accumulation of p53 protein, perhaps through mutational events, may have played a role in this malignant transformation.

DNA analysis at p53 locus in carcinomas arising from pleomorphic adenomas of salivary glands: comparison of molecular study and p53 immunostaining

Where and how frequently p53 abnormalities are involved in the development of pleomorphic adenoma (PA) and its malignant progression to carcinoma was investigated. The presence of p53 gene abnormalities was analyzed in eight patients with carcinoma in pleomorphic adenoma (CPA) by polymerase chain reaction (PCR)-based assays and immunohistochemistry. Normal salivary gland tissue, adenomatous, transitional and carcinomatous areas were microdissected from archival microslides and analyzed for allelic deletions of the p53 gene using two microsatellite markers at the p53 locus; dinucleotide (CA)n repeat and pentanucleotide (AAAAT)n repeat. Loss of heterozygosity (LOH) of the p53 gene was detected in 57% of adenomas, 86% of transitional lesions and 86% of carcinomas. In contrast, overexpression of p53 oncoprotein was noted immunohistochemically in 13% of adenomas, 50% of transitional areas and 75% of carcinomas. All of the tumors with immunoreactivity for p53 oncoprotein demonstrated LOH. Moreover, when LOH was present in adenomatous or transitional areas, the identical LOH was always detected in the corresponding carcinomatous areas in the same CPA tumors. These findings indicate that p53 gene mutation is an early event and occurs frequently at an early stage of precancerous lesions and may be responsible for most cases of malignant transformation of PA.

Genetic alterations in acinic cell carcinoma of the parotid gland determined by microsatellite analysis

We investigated, for the first time, the genetic alterations at certain chromosomal loci in 25 primary parotid acinic cell carcinomas to define the most frequently altered chromosomal regions and their association with pathologic features and DNA content analysis. Our results showed that 21 (84.0%) of the tumors had alteration in at least one of the loci tested. In general, chromosomal regions at chromosomes 4p, 5q, 6p, and 17p were more frequently altered than those on chromosomes 1p and 1q, 4q, 5p, and 6q. Certain markers at 4p15-16, 6p25-qter, and 17p11 regions showed the highest incidence of LOH, suggesting the presence of tumor suppressor genes associated with the oncogenesis of these tumors. LOH was significantly associated only with tumor grade. No apparent correlation between LOH and other clinicopathologic and DNA content characteristics was identified. Our study broadly defined the chromosomal arms and loci that may be targeted for further localization of the minimally deleted regions involved in the tumorigenesis of these tumors.

DNA analysis at p53 locus in adenoid cystic carcinoma: comparison of molecular study and p53 immunostaining

Abnormalities of the p53 tumor suppressor gene were investigated in 22 foci from 14 adenoid cystic carcinomas (ACC) by polymerase chain reaction (PCR)-based assays for dinucleotide (CA)n and pentanucleotide (AAAAT)n repeat polymorphisms and by immunohistochemical staining for oncoprotein expression. Adenoid cystic carcinomas were divided into lower grade (tubular and cribriform) subtypes and higher grade (trabecular and solid) subtypes. Histologically identified tumor cells were precisely microdissected from archival microslides and were used for molecular analysis. The overall frequency of p53 gene mutations detected by PCR-loss-of-heterozygosity (LOH) analysis was 57% and was higher than the frequency of over-expression of p53 oncoprotein detected by immunostaining (43%). In the molecular analysis of individual histological subtype foci, the number of foci with p53 gene mutation was significantly greater in the higher grade subtype foci than in the lower grade subtype foci and was greatest in solid-type foci (100%). In all six tumors in which histologically different foci were present in the same tumors, mutations of the p53 gene were detected. When tumor heterogeneity of the p53 gene was present among different histological foci in the same tumors, the mutations were always detected in the higher grade foci. When lower and higher grade foci were present in the same tumors, the identical mutations detected in the lower grade foci were present in the corresponding higher grade foci. These findings indicate that abnormalities of the p53 gene are involved in carcinogenesis and/or progression of this tumor and, furthermore, suggest that molecular analyses of ACC may provide information of prognostic importance.