Genetic progression and divergence in pancreatic carcinoma

Genetic alterations of pancreatic intraductal lesions adjacent to invasive ductal carcinoma were investigated. We submitted nine foci of ordinary epithelium, 12 foci of nonpapillary hyperplasia, 12 foci of papillary hyperplasia (pap HP), 66 foci of severe ductal dysplasia, and 27 invasive foci from a total of 10 pancreatic carcinomas for genetic analysis. All foci were individually microdissected and allelic losses of 3p, 4q, 5q, 6q, 8p, 9p, 10q, 11q, 13q, 16q, 17p, and 18q were studied. All invasive and severely dysplastic intraductal foci exhibited loss of heterozygosity (LOH) at more than one chromosomal locus. For each case, allelic loss was frequently observed on 9p (severe ductal dysplasia 90%, invasion 100%), 17p (severe ductal dysplasia 80%, invasion 80%), and 18q (severe ductal dysplasia 88%, invasion 88%). Ninety-four percent of severe ductal dysplasia and 96% of invasive foci had multiple LOH. Seventeen percent of nonpapillary hyperplasia and 33% of pap HP showed LOH. Only one focus of pap HP showed multiple LOH. The patterns of allelic loss identified in severe ductal dysplasia were generally conserved in synchronous infiltrating tumors, supporting the paradigm that infiltrating tumors are clonally derived from severe ductal dysplasia. In eight of 10 cases, however, we found frequent genetic heterogeneity in the intraductal lesion, suggestive of genetic progression or diversion. These findings indicate that invasive pancreatic carcinoma evolves through successive and divergent genetic changes with selection of aggressive subclones in the intraductal component.     

Allelic loss in human papillomavirus-positive and -negative vulvar squamous cell carcinomas

Vulvar squamous cell carcinoma (VSCC) is a biologically and morphologically diverse disease, consisting of human papillomavirus (HPV)-positive and -negative tumors that differ in their morphological phenotypes and associated vulvar mucosal disorders. This study analyzed the frequencies of allelic loss (loss of heterozygosity (LOH)) in HPV-positive and -negative VSCCs to identify potential targets for the study of preinvasive diseases, to determine whether HPV status influenced patterns of LOH, and to determine whether these patterns differed from HPV-positive tumors of another genital site, cervical squamous cell carcinomas (CSCC). DNA extracted from microdissected archival sections of two index tumors, one each HPV negative and positive, was analyzed for LOH at 65 chromosomal loci. Loci scoring positive with either sample were included in an analysis of 14 additional cases that were also typed for HPV. Frequencies of LOH at loci were computed in a panel of HPV-positive and -negative VSCCs. Twenty-nine loci demonstrated LOH on the initial screen and were used to screen the remaining 14 tumors. High frequencies of LOH were identified, some of which were similar to a prior karyotypic study (3p, 5q, 8p, 10q, 15q, 18q, and 22q) and others of which had not previously been described in VSCC (1q, 2q, 8q, 10p, 11p, 11q, 17p, and 21q). With the exception of 5q and 10p, there were no significant associations between frequency of LOH and HPV status in VSCC. LOH at 3p and 11q were frequent in both VSCC and CSCC; however, allelic losses at several sites, including 5q, 8q, 17p, 21q, and 22q, were much more common in VSCC. VSCCs exhibit a broad range of allelic losses irrespective of HPV status, with high frequencies of LOH on certain chromosomal arms. This suggests that despite their differences in pathogenesis, both HPV-positive and -negative VSCCs share similarities in type and range of genetic losses during their evolution. Whether the different frequencies of LOH observed between VSCC and CSCC are real or reflect differences in stage and/or tumor size remains to be determined by further comparisons. The role of these altered genetic loci in the genesis of preinvasive vulvar mucosal lesions merits additional study.     

Analysis of clonality and HPV infection in benign, hyperplastic, premalignant, and malignant lesions of the vulvar mucosa

To elucidate the pathogenesis of vulvar carcinomas, we studied clonality and human papillomavirus (HPV) infection in vulvar epithelial diseases. Monoclonal composition was demonstrated in all 9 invasive tumors (squamous cell carcinoma [SCC], 6; basal cell carcinoma, 1; malignant melanoma, 2), 15 of 20 cases of vulvar intraepithelial neoplasia (VIN), 7 of 9 cases of Paget disease, 2 of 6 cases of lichen sclerosus (LS), and 2 of 3 cases of squamous cell hyperplasia (SCH); high-risk type HPV was revealed in 5 of 6 SCCs and 17 of 20 VINs. These observations might imply that a subset of cases of LS and SCH result from a neoplastic proliferation, similar to VINs but not related to infection with high-risk type HPV. In 1 case of SCC with concurrent VIN 3 in an adjacent lesion, both lesions showed the same pattern of X chromosome inactivation and the presence of HPV-16 in episomal and integrated forms, suggesting that monoclonal expansion triggered by high-risk type HPV integration is an early event for carcinogenesis of HPV-associated SCC.     

Review of precancerous vulvar lesions

Classification of squamous vulvar precancerous lesions is based on the concept of vulvar intraepithelial neoplasia (VIN) and incorporates a three grade evaluation of the intensity of dysplastic changes (VIN I, II and III). On the basis of histological features, VIN has been subdivided into the usual VIN (u-VIN) and differentiated VIN (d-VIN), which represent the two basic pathways of the pathogenesis of vulvar squamous cell carcinoma. Although u-VIN is etiologically associated with the human papillomavirus (HPV) infection and histologically corresponds to cervical intraepithelial neoplasia, d-VIN represents the HPV-negative sequence of vulvar carcinogenesis, which is linked to lichen sclerosus (LS) and lichen simplex chronicus (LSC). u-VIN preferentially occurs in relatively young women with a history of cervical, vaginal or vulvar premalignant lesions. On the other hand, d-VIN usually affects postmenopausal women without anamnestic data of other dysplastic lesions of the lower female genital tract. d-VIN is characterized by a higher tendency of stromal invasion than u-VIN and its malignant potential is analogous to carcinoma in situ (VIN III). The histological appearance of d-VIN is subtle with basal atypia and a well-preserved differentiation of the superficial parts of the squamous epithelium, therefore it is frequently misdiagnosed for u-VIN I, LS or LSC in vulvar biopsies. Primarily because of the low diagnostic reproducibility of the u-VIN I category and the doubts about its precancerous potential as well as due to the questionable differentiation between u-VIN II and III, a revised VIN classification was proposed in 2004. The grading of vulvar precancerous lesions was abandoned, the u-VIN I category was discontinued and u-VIN II and III were merged. In the revised terminology, the term u-VIN represents HPV-associated high grade precancerous vulvar lesions (formerly u-VIN II and III) and d-VIN encompasses HPV-negative high grade dysplasias. Keywords: vulvar intraepithelial neoplasia - VIN of the usual type - VIN of the differentiated type - lichen sclerosus - lichen simplex chronicus - HPV.     

Genetic abnormalities and HPV status in cervical and vulvar squamous cell carcinomas

Cervical and vulvar cancers are diseases of the female lower genital tract, and high-risk human papillomavirus (HPV) infection is the most important risk factor for the development of both cancers. However, it is clear that additional genetic events are necessary for tumor progression, particularly in HPV-negative cases. We detected the presence of high-risk HPV16 and HPV18 genomes by gene-specific polymerase chain reaction and searched for common genetic imbalances by comparative genomic hybridization (CGH) in 28 cervical and 8 vulvar tumor samples and 7 cancer cell lines. The presence of the HPV genome was detected in 25/28 (89%) cervical tumors and 6/8 (75%) vulvar tumors. CGH of cervical and vulvar tumor samples revealed a consistent pattern of genetic changes in both cancers. Frequent gains were found in 1q, 3q, 5p, and 8q, and less consistent losses were detected in 2q, 3p, 4p, and 11p. Notably, a high-level amplification of 3q was found in 9/28 (32%) cervical tumors and 1/8 (12.5%) vulvar tumors, indicating a pivotal role of gain of 3q in cervical and vulvar carcinogenesis. Furthermore, gains of 5p identified in 9/28 (32%) cervical tumors and 3/8 (37.5%) vulvar tumors were seldom described, particularly in vulvar tumors. Our findings suggest that cervical and vulvar carcinomas bear similar chromosomal alteration hot spots that largely coincide with common genomic lesions during tumor progression, besides the initiation by infection and integration of oncogenic HPV.     

In the absence of (early) invasive carcinoma, vulvar intraepithelial neoplasia associated with lichen sclerosus is mainly of undifferentiated type: new insights in histology and aetiology

BACKGROUND: Differentiated vulvar intraepithelial neoplasia (VIN) is presumed to be the precursor of invasive squamous cell carcinoma (SCC) of the vulva. It is commonly assumed that differentiated VIN is related to lichen sclerosus (LS). However, evidence for this is limited to a small number of studies describing epithelial alterations adjacent to vulvar SCC. AIM: To study the histology and human papillomavirus (HPV) status in patients with a history of both LS and VIN without coexistent SCC. METHODS: Original biopsy specimens and surgical specimens of patients retrieved from the pathology files were revised for the presence of LS, VIN and (early) invasive SCC, specifically focused on the two different types of VIN: differentiated and undifferentiated. Thereafter, VIN lesions were tested for the presence of HPV DNA. RESULTS: Twenty-seven patients fulfilled the criteria for LS and VIN without SCC. In all 27 patients, LS was found to be related to undifferentiated VIN. Grading yielded the following results: VIN 1 (n=10), VIN 2 (n=11) and VIN 3 (n=6). Additionally, VIN lesions from 26 patients could be tested for the presence of HPV DNA. HPV DNA, predominantly type 16, was present in 8 (31%) of them. Seven of these eight patients had VIN 2 or 3. During follow-up, three patients progressed to (early) invasive carcinoma. In two of these patients, differentiated VIN was observed overlying early invasive SCC. CONCLUSIONS: VIN related to LS without coexisting SCC is likely to be undifferentiated, in contrast to what was previously thought. HPV DNA was demonstrated in 31% of the lesions, and was strongly related to high-grade VIN.     

Loss of heterozygosity in the clonal evolution of flat colorectal neoplasms

In contrast to invasive colorectal carcinomas that develop in typical exophytic adenoma-carcinoma sequences, some invasive cancers may evolve from flat mucosal dysplastic lesions. Despite their relatively small size, these flat colorectal lesions are often associated with high-grade dysplasia and may show an aggressive clinical course. To delineate the genetic pathways in the clonal evolution of these tumors, multiple foci were microdissected from 13 cases and the allelic deletions of 15 chromosomal arms were analysed. Loss of heterozygosity (LOH) was detected most frequently on 17p (77%), followed by 18q (69%), and 5q (54%). In five cases with concomitant low-grade adenomas, only one case showed LOH in low-grade adenoma foci. In high-grade dysplasia with/without submucosal invasion, early and homogeneous LOH of one to several chromosomal arms was detected. Overall, homogeneous and thus early LOH were most frequently detected on 17p (seven of 10 cases with 17p LOH), followed by 3p (two of three cases with 3p LOH), and 5q (four of seven cases with 5q LOH). In addition to homogeneous LOH, the LOH patterns observed in different portions of dysplasias and invasive cancers in individual cases identified several different genetic patterns of tumour progression, either with linear or branching (divergent) trees. Positive immunostaining for p53 was detected in 10 of the 13 cases; of these, five cases were concomitant with 17p LOH in all of the microdissected foci, four cases were concomitant with 17p LOH in a majority of foci and, one case showed retention of 17p. Except for the flat configuration and early 17p LOH, genetic heterogeneity in the flat high-grade dysplastic foci was found to be similar to genetic chaos in the late dysplastic and preinvasive stages of exophytic adenoma. These findings suggest a potentially aggressive course for these neoplasms.     

Distribution of human papillomavirus genotypes in invasive squamous carcinoma of the vulva

Many studies have established a critical role for human papillomavirus (HPV) in the development of anogenital squamous neoplasia. In this report, we show the distribution of 37 high- and low-risk HPV types in 116 cases of invasive squamous vulvar carcinoma. Sections from paraffin-embedded tissue blocks were dissected as necessary to select areas of invasive carcinoma. Clinical and pathologic variables were analyzed using t-tests, univariate odds ratios and logistic regression analysis. Seventy percent of cases were HPV-positive, with an average patient age of 65 years (n=81). HPV-negative cases (n=35) had a higher average age (70 years), but these populations were not statistically different (t=1.65, P=0.10). HPV16 was most common (n=65). Other HPV types were less frequent (HPV33, n=12; HPV45, n=4; HPV52 and 6, each n=3; HPV18, 53 and 62, each n=2). Additional HPV types were identified only once. Multiple infections typically included HPV16 (12/14 cases). Tumors showing low-risk HPV (11 cases) and low-risk HPV only (three cases) were uncommon. Regional node metastasis was documented in 29 of 116 tumors, and 8/9 HPV-positive nodes contained HPV types identical to the primary tumor. Of tumor types, warty carcinoma was most strongly associated with high-risk HPV (odds ratio 4.34, 95% confidence interval 1.32-18.45), particularly high-risk HPVs other than type 16 (odds ratio 9.04, 95% confidence interval 1.60-54.00). Tumors associated with any HPV type (odds ratio 0.40, 95% confidence interval 0.14-1.17), any high-risk type (odds ratio 0.36, 95% confidence interval 0.12-1.08), or type 16 alone (odds ratio 0.34, 95% confidence interval 0.11-1.12) were less likely to metastasize than HPV-negative tumors. Correcting for possible confounding variables, such as patient age and tumor histology, linear logistic regression analysis confirmed this association (high-risk HPV odds ratio 0.28, 95% confidence interval 0.09-0.89).     

Characteristics of vulvar squamous cell carcinoma in Japanese women

Although the presence of racial differences in vulvar squamous cell carcinomas has been suggested, fully analyzed data concerning such tumors in Japanese women have not been reported. A total of 21 vulvar squamous cell carcinomas of Japanese women who lived in north-east Japan, were studied with respect to histological subtype, HPV, p53 and p16(INK4a). The majority of tumors consisted of keratinizing and non-keratinizing types (16/21, 76%), all of which were negative for HPV. The remaining five tumors of basaloid, warty or verrucous types were positive for HPV. HPV-negative tumors showed a trend of greater accumulation of gene abnormalities, including p53 gene mutation, than HPV-positive ones. p16(INK4a) overexpression was shown to not always be a marker for vulvar squamous cell carcinoma in Japanese women with activated high-risk HPV.     

HPV-assoziierte Ver?nderungen an Vulva und Vagina

Non-neoplastic HPV-induced alterations of the vulva and vagina are frequent. The traditional three-tier grading system of vulvar intraepithelial neoplasia (VIN) will be replaced by the definition of usual and simplex type of VIN. The usual type is characterized by a strong association to high-risk HPV infections, the occurrence at younger age and multifocality, mostly associated with non-keratinizing squamous cell carcinoma. The differentiated (or simplex) type is rare and shows an association to older age and p53 alterations and is typically diagnosed co-incidentally with keratinizing squamous cell carcinoma. Vaginal intraepithelial neoplasia (VAIN) is still graded into VAIN 1-3 where VAIN?1 and 2 are mostly associated with low-risk HPV infections and a high spontaneous regression rate whereas VAIN 3 represents a high-risk HPV-associated lesion with capable progression into (micro-)invasive carcinoma. The differential diagnosis between a non-neoplastic condylomatous lesion and VIN common type and VAIN may be aided by p16 immunohistochemistry. The HPV-associated invasive vulvo-vaginal cancers are verrucous carcinoma (low-risk HPV) and the high-risk HPV-induced (non-keratinizing) squamous cell carcinoma (NOS), the condylomatous (warty) carcinoma and the very rare vaginal squamo-transitional carcinoma.     

Premalignant and malignant squamous lesions of the vulva

Vulvar premalignant squamous lesions include low- and high-grade intraepithelial neoplasias. High-grade lesions include usual (classic) and differentiated (simplex) vulvar intraepithelial neoplasia (VIN). Usual VIN (uVIN), the most common, is related to human papilloma virus (HPV), occurs in younger patients, and is frequently multifocal. Differentiated VIN (dVIN), less common, is related to lichen sclerosus and other chronic vulvar dermatoses, occurs in older women, and is usually unifocal. Terminology schemes for premalignant lesions are reviewed. Invasive squamous cell carcinoma also occurs in two distinct clinicopathologic settings. Most conventional keratinizing squamous cell carcinomas arise from a background of dVIN and comprise the majority of invasive squamous tumours. Warty and basaloid invasive squamous cell carcinomas likely develop from uVIN and comprise a minority of invasive tumours. Clinical features, microscopic findings, differential diagnoses, immunoprofiles, prognosis and treatment of premalignant and malignant lesions are addressed.     

Premalignant and malignant squamous lesions of the vulva

Vulvar premalignant squamous lesions include low- and high-grade intraepithelial neoplasias. High-grade lesions include classic (usual) and differentiated (simplex) vulvar intraepithelial neoplasia (VIN). Classic VIN (cVIN), the most common, is related to human papilloma virus (HPV), occurs in younger patients, and is frequently multifocal. Differentiated VIN (dVIN), less common, is related to lichen sclerosus and other chronic vulvar dermatoses, occurs in older women, and is usually unifocal. Terminology schemes for premalignant lesions are reviewed. Invasive squamous cell carcinoma also occurs in two distinct clinicopathologic settings. Most conventional keratinizing squamous cell carcinomas arise from a background of dVIN and comprise the majority of invasive squamous tumours. Warty and basaloid invasive squamous cell carcinomas likely develop from cVIN and comprise a minority of invasive tumours. Clinical features, microscopic findings, differential diagnoses, immunoprofile, prognosis and treatment of premalignant and malignant lesions are addressed.     

Allelic loss of chromosomal arm 8p in breast cancer progression.

Loss of heterozygosity (LOH) of chromosomal arm 8p has been reported to occur at high frequency for a number of common forms of human cancer, including breast cancer. The objectives of this study were to define the regions on this chromosomal arm that are likely to contain breast cancer tumor suppressor genes and to determine when loss of chromosomal arm 8p occurs during breast cancer progression. For mapping the tumor suppressor gene loci, we evaluated 60 cases of infiltrating ductal cancer for allelic loss using 14 microsatellite markers mapped to this chromosomal arm and found LOH of 8p in 36 (60%) of the tumors. Whereas most of these tumors had allelic loss at all informative markers, five tumors had partial loss of 8p affecting two nonoverlapping regions. LOH for all but one of the tumors with 8p loss involved the region between markers D8S560 and D8S518 at 8p21.3-p23.3, suggesting that this is the locus of a breast cancer tumor suppressor gene. We then studied LOH of 8p in 38 cases of ductal carcinoma in situ (DCIS) with multiple individually microdissected tumor foci evaluated for each case. LOH of 8p was found in 14 of the DCIS cases (36%), including 6 of 16 cases of low histological grade and 8 of 22 cases of intermediate or high histological grade. In four of these DCIS cases, 8p LOH was seen in some but not all of the multiple tumor foci examined. These data suggest that during the evolution of these tumors, LOH of 8p occurred after loss of other chromosomal arms that were lost in all tumor foci. Thus, LOH of 8p, particularly 8p21.3-p23, is a common genetic alteration in infiltrating and in situ breast cancer. Although 8p LOH is common even in low histological grade DCIS, this allelic loss often appears to be preceded by loss of other alleles in the evolution of breast cancer.     

Aberrant promoter methylation of SH3GL2 gene in vulvar squamous cell carcinoma correlates with clinicopathological characteristics and HPV infection status

Objective: This study attempted to examine the methylation status of SH3GL2 gene in different types of human vulvar lesions and its correlation with clinicopathological parameters. Methods: Immunohistochemical analysis was used to identify the expression status of SH3GL2 in vulvar squamous cell carcinoma (VSCC), vulvar intraepithelial neoplasia (VIN) and benign vulvar squamous epithelium tissues. Bisulfite genomic sequencing method was used to detect methylation status of the SH3GL2 gene. Clinicopathological correlation of the alterations was analysed by the chi-square tests. Results: Immunohistochemical analysis showed expression of SH3GL2 in VSCC was significantly downregulated than that in VIN and normal vulvar tissues. In accordance with higher frequency of methylation status in SH3GL2, statistical analysis showed methylation status of SH3GL2 was closely related to tumor TNM stage (P=0.003), but not related to age, tumor volume, tumor differentiation, lymph node metastasis and VIN grade. High-methylation status of SH3GL2 showed significant association with HPV infection status. Conclusions: Our results indicated that the methylation status of SH3GL2 gene was associated with the TNM staging and HPV infection status of VSCC, suggesting that it might play a synergistic role in the development of VSCC.     

Differential patterns of allelic loss in estrogen receptor-positive infiltrating lobular and ductal breast cancer

The two main histological types of infiltrating breast cancer, lobular (ILC) and the more common ductal (IDC) carcinoma are morphologically and clinically distinct. To assess the molecular alterations associated with these breast cancer subtypes, we conducted a whole-genome study of 166 archival estrogen receptor (ER)-positive tumors (89 IDC and 77 ILC) using the Affymetrix GeneChip(R) Mapping 10K Array to identify sites of loss of heterozygosity (LOH) that either distinguished, or were shared by, the two phenotypes. We found single nucleotide polymorphisms (SNPs) of high-frequency LOH (>50%) common to both ILC and IDC tumors predominately in 11q, 16q, and 17p. Overall, IDC had a slightly higher frequency of LOH events across the genome than ILC (fractional allelic loss = 0.186 and 0.156). By comparing the average frequency of LOH by chromosomal arm, we found IDC tumors with significantly (P < 0.05) higher frequency of LOH on 3p, 5q, 8p, 9p, 20p, and 20q than ILC tumors. We identified additional chromosomal arms differentiating the subtypes when tumors were stratified by tumor size, mitotic rate, or DNA content. Of 5,754 informative SNPs (>25% informativity), we identified 78 and 466 individual SNPs with a higher frequency of LOH (P < 0.05) in ILC and IDC tumors, respectively. Hierarchical clustering of these 544 SNPs grouped tumors into four major groups based on their patterns of LOH and retention of heterozygosity. LOH in chromosomal arms 8p and 5q was common in higher grade IDC tumors, whereas ILC and low-grade IDC grouped together by virtue of LOH in 16q.     

Genetics of synchronous uterine and ovarian endometrioid carcinoma: combined analyses of loss of heterozygosity,PTEN mutation,and microsatellite instability

Synchronous development of carcinomas in the endometrium and ovaries is a fairly common phenomenon, but distinction of a single clonal tumor with metastasis from 2 independent primary tumors may present diagnostic problems. To determine clonality and the occurrence of progression, we microdissected multiple foci from 17 cases of synchronous endometrioid carcinomas and studied loss of heterozygosity (LOH), microsatellite instability (MI), and PTEN mutations. In 14 of the 17 cases, genetic alterations were either homogeneous or found in only some of the foci. LOH was detected for 10q (4 cases), 17p (2 cases), and 2p, 5q, 6q, 9p, 11q, 13q, and 16q (1 case each). Four cases had the MI phenotype with discordant MI patterns between both tumor sites, thus indicating a biclonal or triple clonal process. In 3 of 6 cases with PTEN mutations, identical mutations in both tumor sites indicated a single clonal neoplasm. Altogether, 14 synchronous tumors were genetically diagnosed as follows: single clonal tumor, characterized by concordant genetic alterations in both tumor sites, including identical LOH, identical PTEN mutations, and/or identical sporadic allelic instability patterns (4 cases); single clonal tumor with genetic progression, homogeneous LOH or identical PTEN mutations in both tumor sites and progressive LOH in ovarian metastatic foci (2 cases); and double (7 cases) or triple clonal tumors (1 case), determined by discordant PTEN mutations, heterogeneous LOH, and/or discordant MI patterns. Thus, 35% of synchronous tumors were monoclonal, 47% were polyclonal, and 18% were undetermined. The favorable prognosis of synchronous endometrioid carcinomas may be due to the occurrence of PTEN mutations in both independent and metastatic tumors, the MI-positive independent primary tumors, and the low frequency of LOH.     

Immunohistochemical localization of telomerase hTERT protein and analysis of clonality in multifocal vulvar intraepithelial neoplasia

Vulvar intraepithelial neoplasias (VINs) are potentially premalignant lesions of the squamous mucosa. The immunohistochemical distribution of the catalytic protein subunit of telomerase (hTERT) and the patterns of X chromosome inactivation were investigated as markers of neoplasia in samples from a patient with multifocal and diffuse VIN. hTERT nuclear staining in VIN correlated with squamous maturation and the degree of nuclear atypia. Normal mucosa revealed faint nuclear staining of parabasal cells and lower intermediate layer squamous cells. Monoclonal composition was demonstrated in 0 of 3 samples of VIN1, 2 of 3 samples of VIN2, and 13 of 13 samples of VIN3. The patterns of X chromosome inactivation indicated intramucosal extension and multifocal origin of individual lesions. Five samples of histologically normal vulvar squamous epithelium revealed a random pattern of X chromosome inactivation, consistent with polyclonal composition. All 19 samples from 9 lesions contained human papillomavirus (HPV)-16 sequences. Neither mutations in the p53 tumor suppressor gene or K-ras oncogenes nor loss of heterozygosity at 7 chromosomal loci were detected in any of the 19 samples of VIN. These results demonstrate that HPV-associated VIN may result from multifocal and diffuse 2-dimensional intraepithelial expansion of an immortalized monoclonal cell population.     

Loss of heterozygosity in fibrocystic change of the breast: genetic relationship between benign proliferative lesions and associated carcinomas

Loss of heterozygosity (LOH), a genetic change frequently detected in cancer, can also occur in benign epithelial foci in the breast. To characterize LOH in benign breast tissue, 32 cases containing the various components of fibrocystic change in the absence of malignancy were studied. Microdissected foci of ductal hyperplasia, apocrine metaplasia, sclerosing adenosis, and morphologically normal terminal duct lobular units (TDLUs) were analyzed for LOH at 14 polymorphic loci representing seven chromosomal arms. LOH was detected in 22% of normal TDLUs (6/27), 17% of adenosis (4/23), 19% of hyperplasia (4/21), and 53% of apocrine metaplasia (10/19) specimens. Because of the high percentage of LOH in apocrine metaplasia in nonneoplastic specimens, the genetic relationship between apocrine metaplasia and cancer was studied in a panel of breast cancer cases. Of 14 examples of apocrine metaplasia adjacent to a carcinoma, seven were found to have LOH with at least one marker. In all seven cases, the tumor and apocrine metaplasia shared LOH at one or more markers. The results demonstrate that LOH occurs frequently in the components of fibrocystic change as well as in normal TDLUs and suggest that foci of apocrine metaplasia can share a genetically altered precursor cell with an associated carcinoma.