Neovascularization in hyperplastic, metaplastic and potentially preneoplastic lesions of the bronchial mucosa

Pathogenesis of Endometriosis: Roles of Retinoids and Inflammatory Pathways

Endometriosis is a nonmalignant, but potentially metastatic, gynecological condition manifested by the extrauterine growth of inflammatory endometrial implants. Ten percent of reproductive-age women are affected and commonly suffer pelvic pain and/or infertility. The theories of endometriosis histogenesis remain controversial, but retrograde menstruation and metaplasia each infer mechanisms that explain the immune cell responses observed around the ectopic lesions. Recent findings from our laboratories and others suggest that retinoic acid metabolism and action are fundamentally flawed in endometriotic tissues and even generically in women with endometriosis. The focus of our ongoing research is to develop medical therapies as adjuvants or alternatives to the surgical excision of these lesions. On the basis of concepts put forward in this review, we predict that the pharmacological actions and anticipated low side-effect profiles of retinoid supplementation might provide a new treatment option for the long-term management of this chronic and debilitating gynecological disease.

Microvascular density of regenerative nodule to small hepatocellular carcinoma by automated analysis using CD105 and CD34 immunoexpression

Background

Angiogenesis is a proliferative process resulting in the development of new blood vessels from existing endothelial cells and is considered crucial for tumor growth and metastasis. Tumor angiogenesis can be quantified by microvascular density (MVD), which is evaluated in highly vascularized tumor areas (hot spots) by immunohistochemical assays using CD34 and CD31 pan-endothelial antibodies. More recently, CD105 has been successfully used for some tumor types because it could discriminate neovascularization. The expression of CD34 and CD105 in hepatocellular carcinomas (HCC) and hepatic precancerous lesions has been reported—although the results for CD105 are controversial—but to the best our knowledge, CD105 has not been previously investigated in dysplastic nodules (DN). We investigated and compared MVD-CD34 and MVD-CD105 immunoexpression in tissues containing different stages of hepatocarcinogenesis, including DN.

Methods

A total of 31 regenerative nodules (RN), 26 DN and 25 small HCC from explants were used for immunohistochemical tests with CD34 and CD105 antibodies. Antibody expression was quantified by computerized image analysis measurement of MVD, areas containing highly positive endothelial cells within the nodules.

Results

The median MVD for CD34 was higher in HCC than in DN and RN (p < 0.01), and was higher in DN compared with RN (p = 0.033). In contrast, MVD with CD105 was higher in RN, and the difference was significant in RN and DN compared with HCC (p = 0.019 and p = 0.012, respectively). When MVD with CD34 and CD105 were compared within a single group, there was a significant predominance of CD105 in RN and DN (p < 0.01). In addition, MVD-C34 in HCC predominated compared with MVD-CD105, but the difference was not statistically significant (p = 0.128).

Conclusions

This study identified a close relationship between CD105 and liver cirrhosis, and that CD34 antibody is a good endothelial marker for hepatic carcinogenesis. There was no difference between the use of CD105 and CD34 antibodies in preneoplastic lesions.

Tryptase-positive mast cells and angiogenesis in keloids: a new possible post-surgical target for prevention

Literature data indicate that mast cells (MCs) are involved in angiogenesis through the release of several pro-angiogenetic factors among which tryptase, a serine protease stored in MC granules, is one of the most active. However, no data are available concerning the role of MCs during keloids' angiogenesis. In this study, we evaluated the correlations of the number of MCs positive to tryptase (MCDPT) and microvascular density (MVD) within a series of 15 keloids and 10 normotrophic scars, by means of immunohistochemistry and image analysis methods. Data demonstrated a significant difference of MVD and MCDPT between keloids and normotrophic scars and a significant correlation between MVD and MCDPT in keloids. Our results suggest that tryptase-positive MCs might play a key role in keloids' angiogenesis. In this context, several tryptase inhibitors might be clinically evaluated as a possible new anti-angiogenetic approach to prevent keloid formation after surgery.

Optical detection of preneoplastic lesions of the central airways

Current routine diagnosis of premalignant lesions of the central airways is hampered due to a limited sensitivity (white light bronchoscopy) and resolution (computer tomography (CT), positron emission tomography (PET)) of currently used techniques. To improve the detection of these subtle mucosal abnormalities, novel optical imaging bronchoscopic techniques have been developed over the past decade. In this review we highlight the technological developments in the field of endoscopic imaging, and describe their advantages and disadvantages in clinical use.

Tumor angiogenesis as a target for dietary cancer prevention

Between 2000 and 2050, the number of new cancer patients diagnosed annually is expected to double, with an accompanying increase in treatment costs of more than $80 billion over just the next decade. Efficacious strategies for cancer prevention will therefore be vital for improving patients' quality of life and reducing healthcare costs. Judah Folkman first proposed antiangiogenesis as a strategy for preventing dormant microtumors from progressing to invasive cancer. Although antiangiogenic drugs are now available for many advanced malignancies (colorectal, lung, breast, kidney, liver, brain, thyroid, neuroendocrine, multiple myeloma, myelodysplastic syndrome), cost and toxicity considerations preclude their broad use for cancer prevention. Potent antiangiogenic molecules have now been identified in dietary sources, suggesting that a rationally designed antiangiogenic diet could provide a safe, widely available, and novel strategy for preventing cancer. This paper presents the scientific, epidemiologic, and clinical evidence supporting the role of an antiangiogenic diet for cancer prevention.

Angiogenesis in pre-malignant conditions

Angiogenesis is an essential process involved in the normal growth and differentiation. In its defective and excessive form, angiogenesis is a crucial event in the progression of many human diseases. Excessive angiogenesis was largely investigated in psoriasis, arthritis, diabetic retinopathy and malignant tumours. Soon after the discovery of angiogenic factors and their inhibitors, the angiogenesis jumped from the experimental studies to clinical application. Tumour-associated angiogenesis is nowadays considered as a priority in oncology based on numerous evidences that showed a significant reduction in tumour growth following anti-angiogenic therapy. However, few data are available on pre-malignant conditions. First evidences on angiogenesis in pre-malignant lesions came from the evaluation of microvessel density (MVD). MVD was found to be significantly increased in a relatively large spectrum of pre-malignant squamous cell lesions, such as in the oral mucosa, skin, uterine cervix, vulva and anal canal. For many of them, a correlation was found between MVD and the expression of vascular endothelial growth factor (VEGF). Based on these data, it was suggested that tumour angiogenesis is not necessarily a characteristic of invasive tumour, but may be an early event during tumourigenesis. Additional evidences came from pre-malignant lesions of glandular epithelia, in which the angiogenic switch was demonstrated by the immunohistochemical expression of VEGF in gastric metaplasia and dysplasia, in atypical adenoma of the colon, atypical hyperplasia and carcinoma in situ of the breast and others. Actually, there are convincing evidences for an active angiogenesis in many cases with pre-malignant conditions, and this supports a more accurate evaluation of different chemopreventive agents.

Assessment of biomarkers in asbestos-exposed workers as indicators of cancer risk

Epidemiological studies have shown that mortality from malignant mesothelioma (MM) and lung cancer have increased with increasing cumulative exposure to asbestos. To investigate whether tumour-related biomarkers can contribute towards the evaluation of the carcinogenic risk in populations exposed to asbestos, the DNA adduct 8-hydroxy-2'-deoxyguanosine (80HdG), interleukine-6 (IL-6), platelet-derived growth factor (PDGF-BB), hepatocyte growth factor (HGF), basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGFbeta) and soluble mesothelin-related peptides (SMRPs) were analysed in a cohort of workers differently exposed to asbestos fibres at the workplace. To document biomarker levels in an unexposed population, 54 age-matched subjects were enrolled. A total of 119 subjects with a history of occupational exposure to asbestos underwent clinical examination and were interviewed by trained personnel, responding to a detailed questionnaire related to duration of asbestos exposure, smoking, and occupational task. According to the occupational tasks, asbestos-exposed subjects were analysed for their asbestos cumulative dose and the association with the biomarkers was evaluated. Among the occupational groups, maintenance workers, pipe fitters and electricians were exposed to a higher cumulative dose of asbestos fibres. Exposure to asbestos significantly increased the steady-state content of 80HdG in DNA. Elevated levels of 80HdG and IL-6 best reflected a high level of SMRPs, which is related to cell transformation. Subjects heavily exposed to asbestos [> 60(ff/cm3) x years] showed also a higher level of angiogenic factors. A combination of angiogenic biomarkers with a specific mesothelioma-biomarker such as SMRPs could be used for close surveillance of workers with a history of asbestos exposure.

Improvement of the specificity of cancer detection by autofluorescence imaging in the tracheo-bronchial tree using backscattered violet light

BACKGROUND

Autofluorescence bronchoscopy (AFB) is a highly sensitive tool for the detection of early bronchial cancers. However, its specificity remains limited due to primarily false positive results induced by hyperplasia, metaplasia and inflammation. We have investigated the potential of blue-violet backscattered light to eliminate false positive results during AFB in a clinical pilot study.

METHODS

The diagnostic autofluorescence endoscopy (DAFE) system was equipped with a variable band pass filter in the imaging detection path. The backscattering properties of normal and abnormal bronchial mucosae were assessed by computing the contrast between the two tissue types for blue-violet wavelengths ranging between 410 and 490 nm in 12 patients undergoing routine DAFE examination. In a second study including 6 patients we used a variable long pass (LP) filter to determine the spectral design of the emission filter dedicated to the detection of this blue-violet light with the DAFE system.

RESULTS

(Pre-)neoplastic mucosa showed a clear wavelength dependence of the backscattering properties of blue-violet light while the reflectivity of normal, metaplastic and hyperplastic autofluorescence positive mucosa was wavelength independent.

CONCLUSIONS

Our results showed that the detection of blue-violet light has the potential to reduce the number of false positive results in AFB. In addition we determined the spectral design of the emission filter dedicated to the detection of this blue-violet light with the DAFE system.

Angiogenesis in preinvasive, early invasive bronchial lesions and micropapillomatosis and correlation with EGFR expression

AIMS

To study the association between morphological changes of the bronchial epithelium and its angiogenic status evaluated by microvessel count (MVC), in order to gain a better understanding of bronchial carcinogenesis. Also, to correlate MVC with epidermal growth factor receptor (EGFR) expression.

METHODS AND RESULTS

Eighty-three biopsy specimens were assessed for MVC: four normal bronchial epithelia, 23 hyperplasias, 26 metaplasias, two mild dysplasias, five moderate dysplasias, nine severe dysplasias, three carcinomas in situ, six early invasive squamous cell carcinomas (EIC) and five cases of micropapillomatosis. We observed a statistically significant difference in terms of MVC between EIC and all other subgroups and between micropapillomatosis and all other subgroups. There was also a statistically significant difference between micropapillomatosis and EIC. We did not observe any difference in MVC between normal mucosa, metaplasias, hyperplasias, dysplasias or carcinoma in situ. EGFR expression was higher in severe dysplasia, carcinoma in situ and EIC, whereas it was very low in micropapillomatosis. A statistically significant difference was observed in the expression profile of EGFR vs. MVC. EGFR expression was increased in severe dysplasia, whereas an increase in MVC occurred only in EIC.

CONCLUSION

During bronchial carcinogenesis, except for micropapillomatosis, EGFR expression appears to be a prerequisite for neoangiogenesis in bronchial carcinogenesis.

In vivo imaging of the bronchial wall microstructure using fibered confocal fluorescence microscopy

RATIONALE

Fibered confocal fluorescence microscopy (FCFM) is a new technique that produces microscopic imaging of a living tissue through a 1-mm fiberoptic probe that can be introduced into the working channel of the bronchoscope.

OBJECTIVES

To analyze the microscopic autofluorescence structure of normal and pathologic bronchial mucosae using FCFM during bronchoscopy.

METHODS

Bronchial FCFM and spectral analyses were performed at 488-nm excitation wavelength on two bronchial specimens ex vivo and in 29 individuals at high risk for lung cancer in vivo. Biopsies of in vivo FCFM-imaged areas were performed using autofluorescence bronchoscopy.

RESULTS

Ex vivo and in vivo microscopic and spectral analyses showed that the FCFM signal mainly originates from the elastin component of the basement membrane zone. Five distinct reproducible microscopic patterns were recognized in the normal areas from the trachea down to the more distal respiratory bronchi. In areas of the proximal airways not previously biopsied, one of these patterns was found in 30 of 30 normal epithelia, whereas alterations of the autofluorescence microstructure were observed in 19 of 22 metaplastic or dysplastic samples, five of five carcinomas in situ, and two of two invasive lesions. Disorganization of the fibered network could be found on 9 of 27 preinvasive lesions, compatible with early disruptions of the basement membrane zone. FCFM alterations were also observed in a tracheobronchomegaly syndrome and in a sarcoidosis case.

CONCLUSIONS

Endoscopic FCFM represents a minimally invasive method to study specific basement membrane alterations associated with premalignant bronchial lesions in vivo. The technique may also be useful to study the bronchial wall remodeling in nonmalignant chronic bronchial diseases.

Microvascular Regeneration in Established Pulmonary Hypertension by Angiogenic Gene Transfer

Pulmonary arterial hypertension (PAH) is characterized by widespread loss of pulmonary microvasculature. Therefore we hypothesized that angiogenic gene therapy would reverse established PAH, in part restoring the lung microcirculation. Three weeks after monocrotaline (MCT) treatment, Fisher 344 rats were randomized to receive a total of either 1.5 x 10(6) syngeneic fibroblasts (FB) transfected with vascular endothelial growth factor A (VEGF), endothelial NO synthase (eNOS), or null-plasmid transfected FBs. Right ventricular systolic pressure (RVSP) was similarly increased in all MCT-treated groups at the time of gene transfer. Animals receiving the null-vector progressed to severe PAH by Day 35 (P < 0.001). In contrast, eNOS gene transfer significantly reduced RVSP at Day 35 compared with Day 21, whereas VEGF prevented further increases in RVSP over the subsequent 2 wk but did not reverse established PAH. RV hypertrophy was significantly reduced in both the eNOS-treated and VEGF-treated groups compared with the null-transfected controls. Fluorescent microangiography revealed widespread occlusion of the pre-capillary arterioles 21 d after MCT treatment, and animals receiving eNOS gene transfer exhibited the greatest improvement in the arteriolar architecture and capillary perfusion at Day 35. Cell-based eNOS gene transfer was more effective than VEGF in reversing established PAH, associated with evidence of regeneration of pulmonary microcirculation.

Overexpression of vascular endothelial growth factor and its receptors in bronchial dypslasia demonstrated by quantitative RT-PCR analysis

Neoangiogenesis is required for the growth of invasive lung carcinoma, however, the role of angiogenesis in the progression of premalignant changes to carcinoma of the lung is less clear. We have evaluated vascular endothelial growth factor (VEGF) expression and microvessel densities (MVDs) in 62 bronchoscopic biopsies from normal, reactive (basal cell hyperplasia (BCH)) and dysplastic bronchial epithelium and in tissue from twenty-seven invasive lung carcinomas in an effort to demonstrate angiogenic activity in these preneoplastic lesions and determine whether it is associated with increased bronchial epithelial VEGF expression. MVDs and VEGF RNA expression measured by quantitative RT-PCR were found to be elevated in comparison to normal bronchial tissue in bronchial dysplasias and invasive lung carcinomas but not in basal cell hyperplasias. Immunohistochemical (IHC) analyses revealed that expression of VEGF arose predominantly from bronchial epithelium. ELISA analysis of lung tumor tissue showed that elevated VEGF protein expression correlated with VEGF RNA levels (r=0.59, p=0.004). Increased expression of VEGF RNA was also found in histologically normal bronchial mucosa from patients with either dysplasia at other sites or a history of heavy tobacco use suggesting a possible field effect in regard to the elaboration of VEGF. Furthermore, analysis of VEGF isoforms and VEGF receptors by semi-quantitative RT-PCR in dysplastic and invasive lesions revealed characteristic altered patterns of expression in dysplasia and early cancer as compared to normal tissue. These results indicate that angiogenesis develops early in lung carcinogenesis and is associated with overexpression of VEGF.

High magnification bronchovideoscopy combined with narrow band imaging could detect capillary loops of angiogenic squamous dysplasia in heavy smokers at high risk for lung cancer

BACKGROUND

We investigated the use of high magnification bronchovideoscopy combined with narrow band imaging (NBI) for the detailed examination of angiogenic squamous dysplasia (ASD). This was carried out in relation to bronchial vascular patterns with abnormal mucosal fluorescence in heavy smokers at high risk for lung cancer.

METHODS

Forty eight patients with sputum cytology specimens suspicious or positive for malignancy were entered into the study. Conventional white light and fluorescence bronchoscopic examination was first performed. Observations by high magnification bronchovideoscopy with conventional white light were made primarily at sites of abnormal fluorescence, and then repeated with NBI light to examine microvascular networks in the bronchial mucosa. Spectral features on the RGB (Red/Green/Blue) sequential videoscope system were changed from the conventional RGB broadband filter to the new NBI filter. The wavelength ranges of the new NBI filter were B1: 400-430 nm, B2: 420-470 nm, and G: 560-590 nm. ASD tissues were also examined using a confocal laser scanning microscope equipped with argon-krypton (488 nm) and argon (514 nm) laser sources.

RESULTS

The microvessels, vascular networks of various grades, and dotted vessels in ASD tissues were clearly observed in NBI-B1 images. Diameters of the dotted vessels visible on NBI-B1 images agreed with the diameters of ASD capillary blood vessels diagnosed by pathological examination. Capillary blood vessels were also clearly visualised by green fluorescence by confocal laser scanning microscopy. There was a significant association between the frequency of dotted vessels by NBI-B1 imaging and tissues confirmed as ASD pathologically (p=0.002).

CONCLUSIONS

High magnification bronchovideoscopy combined with NBI was useful in the detection of capillary blood vessels in ASD lesions at sites of abnormal fluorescence. This may enable the discrimination between ASD and another pre-invasive bronchial lesion.

Epidermal growth factor receptors and cyclooxygenase-2 in the pathogenesis of non-small cell lung cancer: potential targets for chemoprevention and systemic therapy

The epidermal growth factor receptor (EGFR) is part of a family of plasma membrane receptor tyrosine kinases that control many important cellular functions, from growth and proliferation to cell death. Cyclooxygenase (COX)-2 is an enzyme which catalyses the conversion of arachidonic acid to prostagladins and thromboxane. It is induced by various inflammatory stimuli, including the pro-inflammatory cytokines, Interleukin (IL)-1beta, Tumour Necrosis Factor (TNF)-alpha and IL-2. Both EGFR and COX-2 are over-expressed in non-small cell lung cancer (NSCLC) and have been implicated in the early stages of tumourigenesis. This paper considers their roles in the development and progression of lung cancer, their potential interactions, and reviews the recent progress in cancer therapies that are directed toward these targets. An increasing body of evidence suggests that selective inhibitors of both EGFR and COX-2 are potential therapeutic agents for the treatment of NSCLC, in the adjuvant, metastatic and chemopreventative settings.

Subepithelial vascular patterns in bronchial dysplasias using a high magnification bronchovideoscope

BACKGROUND

We have developed a method of high magnification bronchovideoscopy that enables improved observation of subepithelial vascular patterns of the bronchial mucosa. A study was undertaken to investigate the value of high magnification bronchovideoscopy in the detailed examination of dysplasia in the bronchial mucosa of patients with abnormal mucosal fluorescence.

METHODS

Thirty one patients with sputum cytology specimens suspicious or positive for malignancy were entered into the study. Conventional white light examination was first performed under local anaesthesia and fluorescence bronchoscopy was also carried out using a light induced fluorescence endoscopy (LIFE) lung system. A high magnification bronchovideoscope (XBF 200HM2) was then used to examine the microvascular network in the bronchial mucosa at sites of normal and abnormal fluorescence and the images obtained were compared with pathological diagnoses from bronchial biopsy specimens. Vascular area ratios were calculated using image analysing apparatus.

RESULTS

Vascular networks with regular patterns were observed at 20 of 22 abnormal fluorescence sites in biopsy specimens from patients with bronchitis. However, vascular networks with increased vessel growth and complex networks of tortuous vessels of various sizes were observed in 15 of 21 abnormal fluorescence sites in dysplasia specimens. There was a significant difference between bronchitis and dysplasia specimens (OR=25, 95% CI 5.5 to 113, p<0.0001). Mean vascular area ratios from 16 normal bronchial epithelium specimens with normal fluorescence, and 22 bronchitis and 21 dysplasia specimens with abnormal fluorescence were 0.054 (95% CI 0.039 to 0.07), 0.095 (95% CI 0.072 to 0.118), and 0.173 (95% CI 0.143 to 0.203), respectively. The results indicate a statistically significant increase in vascular area in the three groups (p<0.0001).

CONCLUSION

Areas of increased vessel growth and complex networks of tortuous vessels in the bronchial mucosa detected using a high magnification bronchovideoscope at sites of abnormal fluorescence may enable discrimination between bronchitis and dysplasia.

Angiogenesis, thrombospondin, and ductal carcinoma in situ of the breast

Angiogenesis, the growth of new vessels from existing vasculature, plays an essential role in tumour development. The process involves interaction between a variety of cells, growth factors, and components of the extracellular matrix, regulated by pro-angiogenic and anti-angiogenic factors. This review profiles these factors, outlines the available methods for measuring new vessel formation, and discusses the importance of angiogenesis in breast cancer, with emphasis on ductal carcinoma in situ.

Preneoplastic lesions of the lung

Lung cancer is the leading cause of cancer deaths worldwide. If we can define and detect preneoplastic lesions, we might have a chance of improving survival. The World Health Organization has defined three preneoplastic lesions of the bronchial epithelium: squamous dysplasia/carcinoma in situ; atypical adenomatous hyperplasia; and diffuse idiopathic pulmonary neuroendocrine cell hyperplasia. These lesions are believed to progress to squamous cell carcinoma, adenocarcinoma and carcinoid tumors, respectively. In this review we summarize the data supporting the preneoplastic nature of these lesions, and delve into some of the genetic changes found in atypical adenomatous hyperplasia and squamous dysplasia/carcinoma in situ.

Angiogenesis and remodeling of airway vasculature in chronic inflammation

Angiogenesis and microvascular remodeling are known features of chronic inflammatory diseases such as asthma and chronic bronchitis, but the mechanisms and consequences of the changes are just beginning to be elucidated. In a model of chronic airway inflammation produced by Mycoplasma pulmonis infection of the airways of mice or rats, angiogenesis and microvascular remodeling create vessels that mediate leukocyte influx and leak plasma proteins into the airway mucosa. These vascular changes are driven by the immune response to the organisms. Plasma leakage results from gaps between endothelial cells, as well as from increased vascular surface area and probably other changes in the newly formed and remodeled blood vessels. Treatment with long-acting beta2 agonists can reduce but not eliminate the plasma occurring after infection. In addition to the elevated baseline leakage, the remodeled vessels in the airway mucosa are abnormally sensitive to substance P, but not to platelet-activating factor or serotonin, suggesting that the infection leads to a selective upregulation of NK1 receptors on the vasculature. The formation of new vessels and the remodeling of existing vessels are likely to be induced by multiple growth factors, including vascular endothelial growth factor (VEGF) and angiopoietin 1 (Ang1). VEGF increases vascular permeability, but Ang1 has the opposite effect. This feature is consistent with evidence that VEGF and Ang1 play complementary and coordinated roles in vascular growth and remodeling and have powerful effects on vascular function. Regulation of vascular permeability by VEGF and Ang1 may be their most rapid and potent actions in the adult, as these effects can occur independent of their effects on angiogenesis and vascular remodeling. The ability of Ang1 to block plasma leakage without producing angiogenesis may be therapeutically advantageous. Furthermore, because VEGF and Ang1 have additive effects in promoting angiogenesis but opposite effects on vascular permeability, they could be used together to avoid the formation of leaky vessels in therapeutic angiogenesis. Finally, the elucidation of the protective effect of Ang1 on blood vessel leakiness to plasma proteins raises the possibility of a new strategy for reducing airway edema in inflammatory airway diseases such as asthma and chronic bronchitis.

Heterogeneity in microvascular density in lung tumours: comparison with normal bronchus

The aim of this study was to test the hypotheses that (a) microvascular density (MVD) measured in histological sections of resected non-small cell lung carcinomas is an index of angiogenesis and (b) the measurement of MVD in a single block is representative of the overall MVD of the tumour. MVD was quantitated in one block per specimen of 60 lung tumours and nine normal lung tissues, and in 47 blocks taken from different regions of four tumours. Blood vessels were stained with antibody to von Willebrand Factor and MVD was quantitated using two methods: average density throughout the section (a-MVD) and density in the most vascularized area or 'hot spot' (h-MVD). Similar h-MVD values were found in tumours and in normal bronchus, whereas a-MVD was greater in the latter (P < 0.01). When 47 blocks from four tumours were analysed, inter-tumour variation was significant (P < 0.001) in spite of significant intra-tumour variation. The highest MVD value was not necessarily found in the periphery of the tumour. The four tumours were ranked into either two or four tiers according to their overall MVD. In 50 random selections of one block per tumour, the correct ranking was achieved in 68-74% of cases with the two-tier ranking and in 6-16% of cases with the four-tier ranking (h-MVD and a-MVD values respectively). These results suggest that elevated MVD values do not necessarily represent angiogenesis in non-small cell lung carcinomas. When only one block per tumour is examined, the chance of obtaining an accurate estimate of the vascularity of that tumour may be lower than 68%.