Classification of hepatocellular carcinoma according to hepatocellular and biliary differentiation markers. Clinical and biological implications.

Hepatocellular carcinoma (HCC) is a heterogeneous disease. HCC derived from different stages of cellular differentiation may have different clinical and pathobiological behavior. To test the hypothesis that HCC can be classified into two types based on its phenotypic markers (hepatocellular and biliary differentiation), liver tissues from 290 Chinese patients with HCC were studied. Expression of hepatocytic differentiation marker (HEP-PAR-reactive antigen), biliary differentiation markers (AE1-AE3, cytokeratin-19), proliferation markers (Ki-67, proliferating cell nuclear antigen), alpha-fetoprotein, p53, and transforming growth factor-alpha in the tumor tissue were assessed by immunohistochemistry. Hepatocytic differentiation marker was detected in 99.7% and biliary differentiation markers were detected in 29.3% of these tumors. Clinically, no patient with HCC with biliary markers survived for more than 27 weeks compared with a 22.6% survival rate in patients with HCC negative for biliary markers. HCCs positive for the biliary differentiation markers showed features of more aggressive disease in terms of poorer cellular differentiation (P < 0.001) and high-level expression of proliferation markers (Ki-67, P < 0.001; proliferating cell nuclear antigen, P = 0.0114) compared with HCCs without biliary markers. HCCs with biliary markers also had a higher level of expression of alpha-fetoprotein (P < 0.001) and p53 (P = 0.0077). Classification of HCCs based on its phenotypic (differentiation) markers has both clinical and pathobiological implications.     

肺上皮样血管内皮瘤临床病理观察

目的 探讨肺上皮样血管内皮瘤的临床病理特点。方法 4例肺上皮样血管内皮瘤,3例女性,1例男性,年龄28～40岁,无自觉症状或有轻度咳嗽、气短。肺活检或手术切除标本经甲醛固定,石蜡包埋,常规HE及免疫组织化学(Envision法)染色。所用抗体包括CD31、CD34、细胞角蛋白(AEl／AE3)、TTF-1、波形蛋白和上皮膜抗原。结果 本组肺上皮样血管内皮瘤病例女性多于男性,胸部CT显示双肺多发弥漫性小结节影。病理形态特点为结节周边上皮样肿瘤细胞呈花冠状充填于肺泡腔,病变中心为黏液透明样变间质,肺泡壁结构保留,肿瘤细胞胞质内有空泡形成,空泡内偶见红细胞,肿瘤细胞异型性不明显,核分裂和坏死均少见,免疫组织化学染色示CD31、CD34阳性,AE1／AE3偶见灶状阳性,其他抗体呈阴性。结论 肺上皮样血管内皮瘤是一种具有独特临床病理特点的低度恶性血管来源肿瘤。     

Malignant mesothelioma of the peritoneum: case reports and immunohistochemical findings including Ki-67 expression

A malignant mesothelioma (MM) is an aggressive neoplasm, although some patients have shown long-term survival, and factors related to survival remain uncertain. We present three cases of MM of the peritoneum including autopsy results, in which factors related to long-term survival were investigated. Case 1 was a 69-year-old man who died 6 years after the initial diagnosis. In case 2, a 67-year-old woman came to us with abdominal distention and, despite chemotherapy, died 9 months after the initial diagnosis. The patient in case 3 was a 68-year-old man who also had abdominal distention and died 9 months after the initial diagnosis. We studied the clinicopathological appearance and performed immunohistochemical staining including Ki-67 labeling index (Ki-67 LI) in primary and metastatic sites of these cases. The histological findings of case 1 indicated epithelioid type; case 2 and 3 were of biphasic type. Immunohistochemical results were consistent with MM. The Ki-67 LI value for both primary and metastatic sites of case 1 was significantly lower than those in cases 2 and 3. We consider Ki-67 LI to be a useful prognostic indicator for MM of the peritoneum.     

P16 and Ki-67 expression improves the diagnostic accuracy of cervical lesions but not predict persistent high risk human papillomavirus infection with CIN1

Objective: To determine the association between the expression of p16 and Ki-67 and cervical lesions, and to evaluate the role of p16 and Ki-67 as prognostic markers for persistent high risk human papillomavirus (hr-HPV) infection. Methods: Totally 1,154 cases of cervical biopsies were enrolled, 331 cases with negative for dysplasia (NEG), 462 with cervical intraepithelial neoplasia 1 (CIN1), 176 with CIN2, 163 with CIN3 and 22 with cervical squamous cell carcinoma (SCC). Furthermore, 283 women with CIN1 were recruited into 12-month follow-up, and HPV specific gene detection by polymerase chain reaction was used to detect hr-HPV of cervical secretions at 6-month-interval for 12-month follow-up period. 40 women were infected with persistent hr-HPV, 182 with transient infection and 61 unfected with hr-HPV. The expression of p16 and Ki-67 were evaluated by immunohistochemical method. The immunostaining results of p16 and Ki-67 were classified into four categories: negative, 1+, 2+ and 3+. Results: There was significant increase in the expression of p16 (P < 0.001) and Ki-67 (P < 0.001) from NEG to SCC. The expression of Ki-67 (P < 0.001) but not p16 (P = 0.254) significantly increased in CIN2, CIN3. Ratio of p16 (P = 0.215) and Ki-67 (P = 0.495) positivity were not correlated with persistent hr-HPV infection. Conclusion: P16 and Ki-67 can improve the diagnostic accuracy of cervical lesions but can not predict persistent hr-HPV infection with CIN1.     

Immunohistochemical assessment of growth fractions in colorectal adenocarcinomas with monoclonal antibody Ki-67. Relation to clinical and pathological variables

Immunostaining with monoclonal antibody Ki-67 (MAb Ki-67) has been employed to determine the growth fractions in a series of 139 primary adenocarcinomas of the large bowel. A wide range (18.9-71.4%; mean 39.4%; median 37.2%) in the percentage of Ki-67 reacting cells (Ki-67 index) was observed. The Ki-67 index was found to be unrelated to tumour stage, lymph node involvement, and presence of synchronous distant metastases. Mucinous carcinomas showed higher levels of Ki-67 reactivity than non-mucinous adenocarcinomas (P = 0.0003). Among non-mucinous adenocarcinomas a significant inverse correlation was demonstrated between the percentage of Ki-67 stained cells and the degree of differentiation (P = 0.002), and preservation of nuclear polarity (P less than 0.001). Moreover, tumours of patients younger than 45 years were generally characterized by high numbers of proliferating cells. There was no correlation between Ki-67 index and the other clinical and pathological variables examined. In most cases small differences in Ki-67 reactivity were observed in different samples from the same tumour. These results demonstrate that immunohistochemical assay with MAb Ki-67 represents a simple and reliable method for the assessment of proliferative activity in colorectal adenocarcinomas and suggest that Ki-67 labeling may provide information of clinical relevance in the management of patients with large bowel cancer.     

Abnormal Nuclear Structures (Micronuclei,Nuclear Blebs,Strings, and Pockets) in a Case of Anaplastic Giant Cell Carcinoma of the Thyroid: An Immunohistochemical and Ultrastructural Study

The authors report a case of a 70-year-old woman with an anaplastic giant cell thyroid carcinoma, along with immunohistochemical and electron microscopic findings. Histologically, the tumor is characterized by mononucleated and multinucleated giant cells, lack of architectural cohesion, atypical mitoses, and extensive areas of coagulative necrosis. Tumor cells showed AE1/AE3 positivity as well as nuclear overexpression of p53 and ki-67. Semithin sections revealed multiple nuclei with heterogeneous size ranging from micronuclei to large-size (giant) nuclei. Micronuclei were confirmed by electron microscopy that disclosed also the presence of nuclear blebs, strings, and pockets. Morphological findings of these abnormal nuclear structures in conjunction with p53 and Ki-67 nuclear overexpression suggested a faulty mitotic checkpoint/mitotic catastrophe in the progression of anaplastic giant cell thyroid carcinoma.     

Abnormal nuclear structures (micronuclei, nuclear blebs, strings, and pockets) in a case of anaplastic giant cell carcinoma of the thyroid: an immunohistochemical and ultrastructural study

The authors report a case of a 70-year-old woman with an anaplastic giant cell thyroid carcinoma, along with immunohistochemical and electron microscopic findings. Histologically, the tumor is characterized by mononucleated and multinucleated giant cells, lack of architectural cohesion, atypical mitoses, and extensive areas of coagulative necrosis. Tumor cells showed AE1/AE3 positivity as well as nuclear overexpression of p53 and ki-67. Semithin sections revealed multiple nuclei with heterogeneous size ranging from micronuclei to large-size (giant) nuclei. Micronuclei were confirmed by electron microscopy that disclosed also the presence of nuclear blebs, strings, and pockets. Morphological findings of these abnormal nuclear structures in conjunction with p53 and Ki-67 nuclear overexpression suggested a faulty mitotic checkpoint/mitotic catastrophe in the progression of anaplastic giant cell thyroid carcinoma.     

Activation of hepatic stellate cells in liver tissue of patients with fulminant liver failure after treatment with bioartificial liver

We studied the explanted livers from 12 patients with fulminant hepatic failure who were treated with a bioartificial liver and subsequently underwent orthotopic liver transplantation and from 18 patients who underwent orthotopic liver transplantation without previous treatment. Ten normal livers were used as controls. In addition to morphologic evaluation, an immunohistochemical analysis was performed with the monoclonal antibodies for alpha-smooth muscle actin and proliferation marker Ki-67. The expression of these markers was graded semiquantitatively from 0 to 3+ in a blinded fashion. The zonal distribution of activated hepatic stellate cells was also evaluated. In all cases, the hepatic stellate cells were activated and expressed alpha-smooth muscle actin. In all patients with submassive or massive liver cell necrosis, the distribution of activated hepatic stellate cells was predominantly in zone 1 of the acinus (periportal area). In contrast, in cases with early nodular regeneration and no significant fibrosis, the activated hepatic stellate cells were distributed throughout the liver parenchyma, involving zones 2 and 3 of the acinus. Expression of the proliferation marker Ki-67 was graded 3+ in all patients treated with the bioartificial liver who had orthotopic liver transplantation and 2+ in patients who underwent orthotopic liver transplantation only.     

Immunohistochemical analysis of embryonal sarcoma of the liver.

Embryonal sarcoma of the liver is a rare, aggressive malignant tumor that typically occurs in children and teenagers. Microscopic features include spindle, oval, or stellate cells with poorly defined cell borders, nuclear pleomorphism and multinucleation, and variable immunoreactivity to cytokeratin, vimentin, and alpha-1-antitrypsin. Intracellular and extracellular PAS-positive, diastase-resistant hyaline globules are commonly present. The authors evaluated a panel of IHC stains to better define the pattern of immunoreactivity in this tumor. Embryonal sarcomas of the liver were identified from archival files and were immunostained with antibodies: cytokeratin AE1/3, hepatocyte, SMMS, myogenin, calponin, h-caldesmon, desmin, S100, vimentin, CD34, C-kit (CD117), CD10, ALK-1, PE10, Bcl2, p53, and Ki-67. Six cases were identified. Patient age ranged from 6 to 24 years. Tumors ranged from 10 to 20 cm and contained spindled and epithelioid areas with PAS-positive, diastase-resistant globules and atypical cells with focal multinucleation. All cases showed immunoreactivity with vimentin and five showed immunoreactivity with Bcl2. Focal immunoreactivity was seen with cytokeratin AE1/3 in three cases, CD10 in four, calponin in two, desmin in one, and p53 in four. All tumors were negative with hepatocyte, myogenin, CD34, SMMS, h-caldesmon, PE10, ALK-1, and S100. No cytoplasmic staining was seen with C-kit. The proliferation index ranged from 30% to 95%. The diagnosis of embryonal sarcoma is based on typical morphologic features in a large liver tumor occurring in a young patient. The most useful IHC stains help to exclude tumors such as hepatoblastoma, hepatocellular carcinoma, embryonal rhabdomyosarcoma, and other sarcomas.     

Desmoplastic malignant mesothelioma: two cases and a literature review

We present two cases of desmoplastic malignant mesothelioma (DMM) with pathological, immunohistochemical, and ultrastructural features. Each patient showed rapid progress and died within 1 year from appearance of the initial symptoms. Macroscopically, both showed a thickened pleura replaced by a tumor that encased the lung. Microscopic results of each showed that the tumors consisted of a dense fibrous area, with mild nuclear irregularities and hyperchromatism. In case 1, the tumor had invaded the diaphragm, chest wall, and cardiac sac; the mass in case 2 invaded the lung and diaphragm, and distal metastases were seen in the thoracic vertebrae, meninges, and liver. Ultrastructural findings in case 1 showed a few short blunt microvilli on the cell surfaces. DMM is occasionally difficult to distinguish from fibrous pleurisy and solitary fibrous tumor. Immunohistochemical examinations of the present cases showed the expression of cytokeratin and vimentin, and focal positive stainings of antihuman mesothelial cell antibody (HBME-1) in both, whereas CD34 and bcl2 were negative. Solitary fibrous tumor was excluded. Therefore, pathological, ultrastructural, and immunohistochemical findings led us a diagnosis of DMM in each case. The Ki-67 labeling index (Ki-67 LI) of cases 1 and 2 was 25.5 and 15.5, respectively, both high, which suggested malignancy. Widespread immunohistological panels of malignant mesothelioma were not evaluated; Immunohistological markers commonly used for the diagnosis of malignant mesothelioma were not evaluated; however, the high ki-67 LI results and positive HBME-1 staining were helpful factors for the diagnoses of DMM.     

Expression of p53 gene product and cell proliferation marker Ki-67 in Ewing's sarcoma: correlation with clinical outcome

Overexpression of tumor suppressor gene p53, cell proliferation nuclear antigen Ki-67, and proto-oncogene HER-2/neu are associated with poor prognosis in some tumors. We studied p53, Ki-67, and HER-2/neu immunohistochemical expression in archival biopsies of 37 patients with Ewing's sarcoma (ES). Patients with ES were treated at four Israeli hospitals between 1982 and 2000. Formalin-fixed paraffin-embedded tissue sections were stained by immunohistochemistry for p53, Ki-67, and HER-2/neu. More than 300 cells were counted on each slide, and the percentage of positively stained nuclei was computed. p53 overexpression was defined as nuclear staining of >2.3% of cells, Ki-67 overexpression as nuclear staining of >8.3% malignant cells. HER-2/neu staining was scored semiquantitatively on a scale of 0 to 4+. Twenty-two of 37 patients are alive and well, with mean follow-up time of 38 months. There was overexpression of p53 in 16 patients (43%) and of Ki-67 in 21 patients (57%). The correlation between p53 and Ki-67 overexpressions was 0.61. We found no overexpression of HER-2/neu. Median relapse-free survival (RFS) was statistically significantly shorter for patients with p53 overexpression (25 months) than for patients with negative staining (>92 months). The prognostic value of p53 overexpression was also significant after adjusting for tumor location and age. Median RFS was shorter for patients with positive Ki-67 staining (40 months) than for patients with negative staining (80 months) but did not reach statistical significance. Our study suggests that p53 is a predictor of RFS in patients with ES. More patients must be studied to assess the validity of this observation.     

Determination proliferative activity of myeloma cells in histologic material

The assessment of proliferative activity of plasma cells in multiple myeloma has prognostic significance. The percentage of the proliferating plasma cells (plasma cell labelling index--PCLI) at the time of the diagnosis correlates with survival, and is increased during transition from the plateau phase to the relapse. Flow cytometry and immunofluorescence examination of bone marrow aspirates are used for the assessment of the PCLI. This study describes a method for evaluation of PCLI in formalin-fixed, paraffin embedded material. Bone marrow biopsies from 31 patients with relapsing (n = 10) and newly diagnosed (n = 21) multiple myeloma were examined by double immunohistochemical staining: anti-CD 138 (Syndecan 1) and anti--Ki-67. The percentage of plasma cells positive for Ki-67 were counted by an image analysis system. New cases of multiple myeloma showed 0.7 to 12.7% positivity of Ki-67 labelled plasma cells (median 4.75), the relapsing cases showed 4.4 to 22.4% positivity (median 7.75). Statistic analysis revealed prognostic significance (p = 0.046). This study presents a new method for assessment of proliferative activity of plasma cells, which can be used on archived formalin-fixed, paraffin embedded material.     

Expression of MTA2 and Ki-67 in hepatocellular carcinoma and their correlation with prognosis

The aim of this study was to investigate the relationship among MTA2, Ki-67 and HCC patient prognosis. Tissue microarray and immunohistochemistry were used to detect the expression of MTA2 and Ki-67 in HCC samples and corresponding adjacent samples. We found MTA2 and Ki-67 were both increased in HCC tissues than those in adjacent tissues and nuclear MTA2 was associated with Ki-67 (P = 0.019). Moreover, nuclear MTA2 was a risk factor of distant metastasis in patients with HCC andKi-67 showed a negative correlation with histological grade (P < 0.05, P < 0.01, respectively). Multivariate Cox model analysis revealed that Ki-67 expression was an independent prognosis factor in HCC patients (P = 0.020). These results indicated there might be a tight correlation among MTA2, Ki-67 and HCC prognosis. MTA2 combined with Ki-67 might be used to predict HCC patient prognosis.     

Immunohistochemical verification of ductal differentiation in prostate cancer

Recent studies have shown that patients with prostate carcinomas exhibiting ductal differentiation have an unfavourable prognosis compared with those with purely acinar adenocarcinomas. We studied the expression of nine immunohistochemical markers to evaluate their value in delineating carcinomas with and without ductal differentiation. Thirteen tumours showing cellular characteristics and growth patterns typical of ductal differentiation were identified among 110 analysed prostatectomy specimens. The levels of cytoplasmic expression of chromogranine A (69% vs 19%, p = 0.0003) and nuclear expression of p53 (76% vs 12%, p < 0.0001) as well as nuclear expression of Ki-67 (69% vs 26%, p = 0.0047) in the tumour cells, were found to be statistically significantly different in the two tumour categories. Assessment of chromogranine A, p53 and Ki-67 in prostate carcinoma may serve as useful adjunctive diagnostic tools for delineating more aggressive prostate cancer cases exhibiting ductal differentiation.     

肝胆管黏液性囊腺瘤的临床病理分析

目的 观察肝胆管黏液性囊腺瘤的临床病理特点，探讨该病的诊断及鉴别诊断。方法回顾分析5例肝胆管黏液性囊腺瘤的临床表现、组织形态学及免疫表型特征。结果 5例均为女性，平均年龄43.4岁。影像学表现为肝内囊性占位。光镜下囊壁内衬黏液柱状上皮，3/5例上皮下伴有卵巢样间质，免疫表型：上皮细胞CK(AE1/AE3)(5/5)、CK(AE3)(5/5)、EMA(4/5)、CA199(5/5)、PR(1/5)、p53(1/5)、E-cadherin(2/5)呈阳性表达，不表达Ki-67及c-erbB-2；间质细胞vimentin(5/5)、SMA(4/5)及ER(2/5)、PR(3/5)呈阳性表达。结论 肝胆管黏液性囊腺瘤较为罕见，好发于中年女性，囊壁内衬黏液柱状上皮，可伴有卵巢样间质，有恶性潜能，可以发展为交界性变甚至癌变。手术完整切除预后好。     

Induction of proliferating cell nuclear antigen and Ki-67 expression by cytomegalovirus infection

With the goal of facilitating viral reproduction, cytomegalovirus (CMV) induces changes in the host cell replication machinery. Very little information is available, however, on the effects brought about by CMV on proliferating cell nuclear antigen (PCNA) and Ki-67 expression in infected cells. Fifty-five paraffin-embedded tissue samples (43 gastrointestinal, 10 skin, and 2 kidney biopsies) with both histological and immunohistochemical evidence of CMV infection were investigated for PCNA and Ki-67 expression by the avidin– biotin–peroxidase method. Of the 55 cases studied, 47 were positive for PCNA and 46 for Ki-67. PCNA and Ki-67 immunostaining was more striking in CMV-immunoreactive, inclusion-free cell nuclei, whereas cell nuclei exhibiting well-developed CMV inclusions either showed a weak peripheral signal for both proliferation markers, or were completely negative. Enhanced PCNA and Ki-67 expression appears to be among the changes induced by CMV infection in host cells. Moreover, this induction seems to reach its peak during the earlier phases of CMV infection and abate as the infection proceeds to its inclusion-forming phases, when a sufficiently high viral load would have been attained. © 1998 John Wiley & Sons, Ltd.     

The specificity of expression of molecular biological markers in tumors of the mammary gland

Data are described on a retrospective immunohistochemical study of the Ki-67, PCNA, Bcl-2, BAX, BclX and VEGF expression in tumors of two groups of patients with breast cancer (BC) and with the favorable and unfavorable clinical courses. A reliably high level of VEGF expression was detected in tumors of patients with an early BC relapse. Apart from VEGF, higher levels of the Ki-67 and PCNA expression were registered in tumors of the discussed patient's category. It can be suggested that the expression parameters of VEGF, Ki-67 and PCNA in the primary tumor can be made use of in evaluating the BD prognostications or describing the features of high-risk groups with a high probability of early disease relapses.     

Immunogold labelling of PCNA and Ki-67 antigen at the ultrastructural level in laryngeal squamous cell carcinoma and its correlation with lymph node metastasis and histological grade

Streptavidin-gold was used for the immunolocalization of PCNA and Ki-67 antigen at the ultrastructural level with a postembedding technique in biopsies of 15 patients with laryngeal squamous cell carcinoma. Positive immunoelectron staining was obtained in 9 cases for PCNA (60%) and in 8 cases for Ki-67 (53%). PCNA was predominantly found in heterochromatin of the nucleus of laryngeal carcinoma cells in a granular pattern. Positivity for PCNA was not found in nucleoli. In 4 cases, positive staining was observed both in nucleus and cytoplasm. In the cytoplasm, it was found to be present on the endoplasmic reticulum and on ribosomes throughout the cytoplasm. Ki-67 antigen was localized in the nucleus where it was associated with heterochromatin and euchromatin. It was also observed in nucleoli in all cases. Cytoplasmic localization of Ki-67 antigen was similar to that of PCNA. All 8 cases that were positive for Ki-67 were also positive for PCNA. Control incubations did not result in labelling with steptavidin-gold particles for both antigens. A significant correlation between PCNA and Ki-67 expression in association with pathological characteristics such as nodal status and histological grade was not found. Our data indicate that Ki-67 antigen staining correlates with PCNA labelling, whereas a relationship between proliferation markers and tumour progression was not found.     

Expression of p53 protein,PCNA, and Ki-67 in osteosarcomas of bone.

Expressions of p53 protein, a product of the tumor suppressor gene were studied in osteosarcomas relating to various prognostic factors. Thirty-four osteosarcomas were investigated immunohistochemically with a monoclonal antibody clone PAb240, which recognizes a common conformational epitope of mutant p53 proteins and another clone PAb1801, which reacts with both wild- and mutant-type p53 proteins. The results were compared with expressions of proliferating cell nuclear antigen (PCNA) and Ki-67 providing a simple method for the assessment of growth fractions of tumors. PAb240 stained nuclei and cytoplasm of tumor cells in 8 of 34 osteosarcomas (23.5%), whereas PAb1801 reacted in all 34 osteosarcomas (100%). Fifteen tumors (44.1%) showed positivity for PAb1801 in more than half of the tumor cells. Twelve patients were alive and thirteen were dead. Tumors from 9 patients (75%) who survived revealed only focal positive immunoreactions with PAb1801 and tumors from 6 patients (46.1%) who died revealed diffuse reactions. Twelve cases (35.3%) showed a high PCNA index (> 40%) and fibroblastic osteosarcomas revealed the highest PCNA positivity. Twenty-two cases (64.7%) revealed a very low Ki-67 index (less than 10%) and Ki-67 index showed a good correlation with PCNA positivity (r = 0.6247). Expressions of both wild-and mutant-type p53 protein, PCNA, and Ki-67 were not correlated with other clinical or pathological parameters.     

Nodular hyperplasia of Bartholin's gland

AIMS: There has been very little mention of benign solid lesions of the Bartholin's gland (BG) in pathology and gynaecology textbooks, and very few cases have been reported in the literature. Among these lesions, the distinction between nodular hyperplasia (NH) and adenoma has not been well defined. We report ten cases of NH of the BG, describe their clinicopathological, immunohistochemical and ultrastructural findings, and review the literature. METHODS: We examined retrospectively all lesions involving BGs from our surgical pathology records from 1990 to 2004 with emphasis on NH. To separate NH from adenoma, we applied the criteria proposed by Koenig and Tavassoli. Special stains (PAS with and without prior digestion, Mayer's mucicarmine and Alcian blue with and without hyaluronidase) and immunohistochemistry (CAM5.2, AE1/AE3, HMWK, monoclonal CEA, EMA, ER, PR, ALA, SMA, Ki-67, p53 and polyclonal CEA) were performed on NHs. Two cases were examined ultrastructurally. RESULTS: Using specific criteria, ten cases (age range 23-45 years; mean 36.1) of NH were identified, two of which were diagnosed previously as adenoma, but re-classified as NH. Clinically, these lesions were described either as Bartholin's duct cysts (BDCs) or vulvar lumps. Grossly, NHs were solid, tan and unencapsulated, measuring 12.5-45.0 mm in maximum dimension (mean 23.8). Histologically, the NHs were composed of a proliferation of mucus-secreting acini with preservation of the normal duct-to-acinar relationship. Chronic inflammation and squamous metaplasia were present. Eight lesions focally involved the surgical margins. Intracytoplasmic and intra-luminal secretions were positive for PAS with and without digestion, Alcian blue with and without hyaluronidase and mucicarmine. All lesions showed positive staining for CAM5.2, AE1/AE3, HMWK, EMA, and polyclonal CEA. There was negative staining for Ki-67, ER, PR, ALA, p53 and monoclonal CEA. Periacinar myoepithelial cells stained for SMA. Ultrastructurally, the findings included abundant intracytoplasmic secretory granules, granulofibrillar bodies, prominent Golgi and ribosomes. Myoepithelial cells were identified. There was no tumour recurrence or malignant transformation in eight patients with clinical follow-up. CONCLUSION: NH of the BG is a rare lesion with benign behaviour. It is a distinct entity and can be separated histologically from an adenoma.