Expression of vascular endothelial growth factor (VEGF) and its receptors (VEGF-R1 [Flt-1] and VEGF-R2 [KDR/Flk-1]) in tumorlets and in neuroendocrine cell hyperplasia of the lung

Distinct Expression Patterns of VEGFR 1-3 in Gastroenteropancreatic Neuroendocrine Neoplasms: Supporting Clinical Relevance, but not a Prognostic Factor

INTRODUCTION

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) are an increasing tumor entity. Since many patients are diagnosed at an advanced stage, treatment is still challenging and dependent on many tumor and patient specific factors. Therefore, the aim of the present study was to elucidate the expression rates and the prognostic value of vascular endothelial growth factor receptor (VEGFR) 1-3 in GEP-NENs. A potential association to immune checkpoint markers was further investigated.

MATERIAL AND METHODS

The expression levels of VEGFR 1-3 were analyzed by immunohistochemistry and correlated with the expression of the checkpoint markers PD-1 and PD-L1. Furthermore, the tumor samples of 249 GEP-NEN patients were studied and correlated with overall survival rates and clinicopathological features. Kaplan-Meier analyses and the log rank test were used for survival analyses. Categorical variables were compared by the χ2 test.

RESULTS

The most common primary tumor site was the small intestine (50.6%), followed by the pancreas (25.7%). VEGFR 1 was highly expressed in 59%, VEGFR 2 in 6.4%, and VEGFR 3 in 61.8% of the analyzed samples. The expression of VEGFR 1-3 was not significantly associated with survival rates. Pancreatic NENs had the highest expression of VEGFR 1 and 3 in 80% of the cases. VEGFR 1-3 positivity correlated with the expression levels of immune checkpoint markers.

DISCUSSION

VEGFR 1-3 show a distinct expression pattern in different subgroups of neuroendocrine neoplasias indicating a conceivable target. Moreover, there was a substantial association between VEGFRs and immune checkpoint markers. Taken together, anti-VEGFR therapy represents a promising therapeutic approach in GEP-NEN patients and should be addressed in future studies.

Carcinoid Tumorlets Co-Existing with Chronic Pulmonary Inflammatory Processes: Imaging Findings and Histological Appearances

Background

Pulmonary carcinoid tumorlets (PCT) are incidental histologic or radiologic discoveries that are localized neuroendocrine tumors whose proliferation is associated with chronic pulmonary inflammatory processes. This study assessed the imaging findings and histological appearances of PCT co-existing with chronic pulmonary inflammatory processes.

Material/Methods

We performed a retrospective study of 14 patients with incidentally-found PCT with co-existing chronic pulmonary inflammatory processes who underwent preoperative X-rays and CT between 1 January 2003 and 31 December 2012. The clinical symptoms, X-rays, CT imaging findings, and histological appearances were retrospectively evaluated.

Results

Twelve women and 2 men were found to have PCT, with a mean age of 55.29±13.90 years (range 25–74 years) at diagnosis. Among these 14 patients, hemoptysis, cough, chest pain, expectoration, and chest tightness were found in 9 (64.3%), 5 (35.7%), 4 (28.6%), 3 (21.4%), and 1, respectively. For most patients, we could not find any small nodules on the X-ray or CT images. However, indirect imaging findings of bronchiectasis (85.7%, 12/14), atelectasis (57.1%, 8/14), inflammation (92.8%, 13/14), tuberculosis (7.1%, 1/14), and lung cancer (7.1%, 1/14) were found in all 14 patients.

Conclusions

PCT occurs most commonly in middle-aged women who have chronic pulmonary inflammatory processes such as bronchiectasis, atelectasis, and inflammation. Although there are no specific symptoms or direct imaging findings in these patients, our results showed that patients who have bronchiectasis, atelectasis, or recurrent pulmonary infection are at increased risk for PCT.

Pulmonary Scedosporium apiospermum Infection with Pulmonary Tumorlet in an Immunocompetent Patient

Scedosporium apiospermum is an opportunistic fungus that can cause various types of infections, including localized infections and life-threatening disseminated infections, particularly in immunocompromised patients. Treatment is especially challenging due to its multidrug resistance. We herein report the case of a 73-year-old woman who was non-immunocompromised but developed S. apiospermum lung infection and a pulmonary tumorlet. To our knowledge, this is the first report of the coexistence of pulmonary S. apiospermum infection and tumorlet. The lung lesion was successfully treated by surgical excision without any antifungal agents, and no recurrence of the tumorlet or S. apiospermum infection has occurred.

A case of lung tumorlets secondary to pulmonary hypoplasia with recurrent haemoptysis

Most patients with lung tumorlets are usually asymptomatic, and most diagnoses are incidental findings during microscopic lung examinations at autopsy or after excision of a tissue lesion. A 73-year-old woman was admitted to our hospital due to recurrent haemoptysis. Chest computed tomography demonstrated right inferior lobe collapse with bronchiectasis. Bronchoscopic examination revealed the right inferior lobar bronchus to be filled with blood clots. Haemoptysis persisted even after two arterial embolization trials and occlusion with endobronchial Watanabe spigot. Therefore, right lower lobectomy was performed, and multiple tumorlets on lobar hypoplasia were observed on histopathological examination of the excised specimen. We believe that the haemoptysis in our patient was possibly caused by the lung tumorlets secondary to lobar hypoplasia.

Neuroendocrine Neoplasia in Extranodal Marginal Zone Lymphoma of Mucosa-Associated Lymphoid Tissue (MALT Lymphoma) of the Lung: A Case Report and Immunohistochemistry Analysis of Eight Pulmonary MALT Lymphomas

Carcinoid tumorlets are peribronchiolar proliferations of neuroendocrine cells often associated with lung scars. Extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma) is a non-Hodgkin's lymphoma that frequently involves the gastrointestinal tract but less commonly is described in the lung. Simultaneous occurrence of neuroendocrine neoplasms and MALT lymphoma is extraordinarily rare and has predominately been reported in the gastrointestinal tract. In this article, we describe the case of a 73-year-old female with coexisting pulmonary MALT lymphoma and carcinoid tumorlets of the right middle lobe. Retrospective series of 8 pulmonary MALT lymphomas are evaluated for neuroendocrine neoplasia by immunohistochemistry. No correlation between MALT lymphoma and neuroendocrine neoplasia was identified in this case series. While the concurrence of these distinctive neoplasms is most likely coincidental, the presence of a common risk factor, or one neoplasm as a risk factor for the other, deserves study of a larger group of pulmonary MALT lymphomas.

Interferon alpha and rapamycin inhibit the growth of carcinoid and medullary thyroid cancer in vitro

Neuroendocrine tumors (NETs) are highly vascularized neoplasms characterized by rising incidence. Moreover, the neuroendocrine cells were shown to express vascular endothelial growth factor (VEGF) and VEGF receptors. Therefore, angiomodulators could be potentially a new group of drugs enhancing still unsatisfactory effectiveness of NET therapy. The aim of this study was to assess the direct influence of angiomodulators: VEGF and five endogenous and exogenous antiangiogenic compounds (endostatin, interferon alpha [IFNα], rapamycin, JV1-36, semaxinib [SU5416]) on the growth of two NET cell lines: lung carcinoid H727 cell line and medullary thyroid cancer TT cell line in vitro. IFNα and rapamycin induced the inhibitory effect on H727 and TT cell viability and proliferation, increasing apoptosis and arresting the cell cycle. Also semaxinib (10(-5)M) inhibited proliferation of both cell lines. VEGF and endostatin did not influence the growth of H727 and TT cells. The inhibitory effect of IFNα, rapamycin and semaxinib on carcinoid and medullary thyroid cancer growth was revealed in our in vitro study, although some other antiangiogenic agents did not directly influence H727 and TT cell growth. Thus, IFNα and mTOR inhibitors as multidirectionally acting drugs with antiangiogenic effect could be potentially efficient in treatment of neuroendocrine tumors and are worth further studies.

Tyrosine phosphorylation modulates the vascular responses of mesenteric arteries from human colorectal tumors

The aim of this study was to analyze whether tyrosine phosphorylation in tumoral arteries may modulate their vascular response. To do this, mesenteric arteries supplying blood flow to colorectal tumors or to normal intestine were obtained during surgery and prepared for isometric tension recording in an organ bath. Increasing tyrosine phosphorylation with the phosphatase inhibitor, sodium orthovanadate produced arterial contraction which was lower in tumoral than in control arteries, whereas it reduced the contraction to noradrenaline in tumoral but not in control arteries and reduced the relaxation to bradykinin in control but not in tumoral arteries. Protein expression of VEGF-A and of the VEGF receptor FLT1 was similar in control and tumoral arteries, but expression of the VEGF receptor KDR was increased in tumoral compared with control arteries. This suggests that tyrosine phosphorylation may produce inhibition of the contraction in tumoral mesenteric arteries, which may increase blood flow to the tumor when tyrosine phosphorylation is increased by stimulation of VEGF receptors.

Pulmonary carcinoid tumorlet without underlying lung disease: analysis of its relationship to fibrosis

Pulmonary carcinoid tumorlet is a rare pathology and appears to be always associated with other lesions such as bronchiectasis and fibrosis. While the caus e-effect relationship between tumorlet and the accompanying pathological changes in the surrounding mesenchymal tissue remains to be defined, it has been postulated that pulmonary fibrosis may be the primary pathology underlying the development of tumorlet. In this paper, we present a case where a tumor (<0.5 cm) was detected in the right upper lobe of a 71-year old woman. Cells of the tumor displayed markers characterizing for their neuroendocrine origin. No histological evidence for inflammation, interstitial fibrosis and remodeling of vascular structure was observed. However, immunohistochemistry assay demonstrated a strong production of the profibrotic factors VEGF and TGF-β1 by tumor cells. These findings suggest that carcinoid tumorlet can be an isolated lesion and pulmonary fibrosis that "often co-exists" with tumorlet may be secondary to the paracrine effects of fibrotic growth factors produced by tumorlet.

sVEGF R1 and Tie-2 levels during chemotherapy of lung cancer patients

Angiogenesis plays important role in tumor growth and development. Protein ligands and their receptor tyrosine kinases are crucial in tumor related angiogenesis. Ligand/receptor systems such as vascular endothelial growth factor (VEGF), and tyrosine kinase with immunoglobulin-like and epidermal growth factor homology domains (Tie) family play important role in this phenomenon. The aim of this study was to evaluate the concentration of soluble receptor of VEGF (sVEGF R1) and Tie-2 domain in plasma of lung cancer patients before and after chemotherapy. Forty four lung cancer patients, 11 with small lung cancer (SCLC), 5 females and 6 males (mean age 60.2, range 39-72 years), and 33 patients with non-small cell lung cancer (N-SCLC), 6 females and 27 males (mean age 61.9, range 42-78 years) received four courses of chemotherapy. Control group consisted of 44 patients with COPD, 4 females and 40 males (mean age 37.1, 18-60 years). In all cases clinical partial response was achieved. Both sVEGF R1 and Tie-2 concentrations were elevated in cancer group before treatment compared with control: sVEGF (pg/ml): 60.7 and 66.2 vs. 48.8 and Tie-2 (ng/ml): 37.3 and 37.5 vs. 30.7 in SCLC and N-SCLC vs. C, respectively. Treatment decreased sVEGF R1 (pg/ml): 66.7 vs. 11.6 (p < 0.05) and 66.2 vs. 14.39 (p < 0.001), and Tie-2 (ng/ml): 37.3 vs. 26.3 (p < 0.05) and 37.5 vs. 25.7 (p < 0.001) in SCLC and N-SCLC, respectively. We conclude that VEGF R1and Tie-2 receptors may play important role in lung cancer development and their receptor concentrations may reflect the patients' response to treatment.

Neuroendocrine tumors of the lung

Neuroendocrine tumors may develop throughout the human body with the majority being found in the gastrointestinal tract and bronchopulmonary system. Neuroendocrine tumors are classified according to the grade of biological aggressiveness (G1-G3) and the extent of differentiation (well-differentiated/poorly-differentiated). The well-differentiated neoplasms comprise typical (G1) and atypical (G2) carcinoids. Large cell neuroendocrine carcinomas as well as small cell carcinomas (G3) are poorly-differentiated. The identification and differentiation of atypical from typical carcinoids or large cell neuroendocrine carcinomas and small cell carcinomas is essential for treatment options and prognosis. Pulmonary neuroendocrine tumors are characterized according to the proportion of necrosis, the mitotic activity, palisading, rosette-like structure, trabecular pattern and organoid nesting. The given information about the histopathological assessment, classification, prognosis, genetic aberration as well as treatment options of pulmonary neuroendocrine tumors are based on own experiences and reviewing the current literature available. Most disagreements among the classification of neuroendocrine tumor entities exist in the identification of typical versus atypical carcinoids, atypical versus large cell neuroendocrine carcinomas and large cell neuroendocrine carcinomas versus small cell carcinomas. Additionally, the classification is restricted in terms of limited specificity of immunohistochemical markers and possible artifacts in small biopsies which can be compressed in cytological specimens. Until now, pulmonary neuroendocrine tumors have been increasing in incidence. As compared to NSCLCs, only little research has been done with respect to new molecular targets as well as improving the classification and differential diagnosis of neuroendocrine tumors of the lung.

Tumorlets, multicentric carcinoids, lymph-nodal metastases, and long-term behavior in bronchial carcinoids

BACKGROUND

The clinical significance of lymph-node metastases, multicentric forms, and tumorlets in bronchial carcinoids is still a matter of debate. Aim of this study was to analyze their prevalence and clinical significance in a series of 123 bronchial carcinoids.

PATIENTS AND METHODS

Nodal dissection and serial sections of resected lung parenchima for research of multicentric forms and tumorlets were performed in most patients. Survival curve was produced using the Kaplan-Meyer method and multivariate analysis by the Cox proportional hazard model.

RESULTS

Lymph-node involvement was present in 14% of typical (14 of 100) and 13.04% of atypical carcinoids (3 of 23). Multicentric forms (syncronous carcinoids or tumorlets) were found in 11.3% of the total with a negative impact on survival (p = 0.021). Multiple tumorlets were found in 7.3% of all cases at the standard pathologic examination, but whenever accurate palpation and serial sections of the surgical specimen were performed, the percentage reached 24% of the cases. Overall survival was 98.2%, 95.8%, and 83.9% for typical and 71.6%, 57.3%, and 24% for atypical carcinoid respectively at 5, 10, and 15 years. Time from surgery was significantly directly correlated with recurrences (p < 0.0001) and disease related death (p = 0.0002).

CONCLUSIONS

A high prevalence of tumorlets, multiple carcinoids, and lymph-nodal involvement was found in our series. On the basis of these observations bronchial carcinoids always require major surgical procedures with systematic nodal dissection, and a careful search for multifocal lesions should always be performed. Follow-up should always be accurate and protracted, due to the frequency of very long-term relapses (often more than 10 years after surgery).

Prognostic significance of the expression of vascular endothelial growth factors A, B, C, and D and their receptors R1, R2, and R3 in patients with nonsmall cell lung cancer

BACKGROUND

Lung cancer is the leading cause of cancer death in the world. The objective of this study was to investigate the expression of vascular endothelial growth factors (VEGFs) and their receptors (VEGFRs) in patients with nonsmall cell lung cancer (NSCLC) and its correlation with the prognosis for patients with lung cancer.

METHODS

The expression status of VEGFs and VEGFRs was examined in 48 nonconsecutive specimens of primary lung cancer by immunohistochemistry. Correlations between the expression of VEGFs and VEGFRs and clinicopathologic parameters were analyzed.

RESULTS

Nineteen of 48 samples (39.6%) were moderately/highly immunoreactive for VEGF-A, 6 samples (12.5%) were reactive for VEGF-B, 14 samples (29.2%) were reactive for VEGF-C, 11 samples (22.9%) were reactive for VEGF-D, 20 samples (41.7%) were reactive for VEGFR1, 26 samples (54.2%) were reactive for VEGFR2, 20 samples (41.7%) were reactive for VEGFR3, and 19 samples (39.6%) were reactive for nuclear expression of VEGFR3. Patients with moderate/high VEGF-C, VEGFR1, and VEGFR2 expression had worse survival, whereas patients with moderate/high VEGF-D and nuclear VEGFR3 expression had better survival. After adjusting according to tumor stage, VEGF-B and VEGF-D expression had a significant correlation with worse survival in patients with stage I and II disease. Patients with stage III and IV disease who had VEGFR1 and VEGFR2 expression had worse survival, whereas the expression of VEGF-D was correlated significantly with better survival. Finally, stage, VEGF-D expression, and VEGFR1 expression were significantly independent prognostic predictors.

CONCLUSIONS

The results of the current study indicated that the over-expression of VEGFs and VEGFRs plays an important role in the survival of patients with NSCLC. The inclusion of angiogenic factors in the standard pathologic study of lung cancer may improve the clinical evaluation of patients with NSCLC.

Cholangiocyte proliferation and liver fibrosis

Cholangiocyte proliferation is triggered during extrahepatic bile duct obstruction induced by bile duct ligation, which is a common in vivo model used for the study of cholangiocyte proliferation and liver fibrosis. The proliferative response of cholangiocytes during cholestasis is regulated by the complex interaction of several factors, including gastrointestinal hormones, neuroendocrine hormones and autocrine or paracrine signalling mechanisms. Activation of biliary proliferation (ductular reaction) is thought to have a key role in the initiation and progression of liver fibrosis. The first part of this review provides an overview of the primary functions of cholangiocytes in terms of secretin-stimulated bicarbonate secretion--a functional index of cholangiocyte growth. In the second section, we explore the important regulators, both inhibitory and stimulatory, that regulate the cholangiocyte proliferative response during cholestasis. We discuss the role of proliferating cholangiocytes in the induction of fibrosis either directly via epithelial mesenchymal transition or indirectly via the activation of other liver cell types. The possibility of targeting cholangiocyte proliferation as potential therapy for reducing and/or preventing liver fibrosis, and future avenues for research into how cholangiocytes participate in the process of liver fibrogenesis are described.

Taurocholate feeding to bile duct ligated rats prevents caffeic acid-induced bile duct damage by changes in cholangiocyte VEGF expression

Cholangiocytes are the target cells in cholestatic models of ductal hyperplasia including bile duct ligation (BDL). We have shown that: (i) cholangiocytes express VEGFR-2 and VEGFR-3; (ii) VEGF-A and VEGF-C stimulate cholangiocyte proliferation via an autocrine mechanism; and (iii) chronic administration of VEGF-A prevents cholangiocyte damage induced by hepatic artery ligation. Caffeic acid phenethyl ester (CAPE) induces growth inhibition in different cells. Taurocholic acid (TC) protects cholangiocytes against injury induced by parasympathetic or sympathetic denervation. The aims of this study were to determine if: (i) CAPE induces bile duct damage; and (ii) TC prevents CAPE-induced bile duct damage by increasing cholangiocyte VEGF expression.

METHODS

Normal and BDL rats (immediately after surgery) were fed 1% TC or control diet in the absence/presence of daily IP injections of CAPE (10 mg/Kg BW). One week later, we evaluated: (i) cholangiocyte apoptosis, proliferation and ductal mass in liver sections; (ii) functional activity by measuring secretin-stimulated bile and bicarbonate secretion; and (iii) VEGF-A/C and VEGFR-2/R-3 expression in liver sections. In vitro, BDL cholangiocytes were exposed to CAPE (40 microM) in the absence/presence of TC (40 microM) with and without pretreatment with VEGF receptor inhibitors before evaluating cholangiocyte apoptosis and proliferation.

RESULTS

Chronic CAPE administration to BDL rats increased cholangiocyte apoptosis and decreased ductal mass. This effect was associated with reduced expression of VEGF-A, VEGF-C, VEGFR-2 and VEGFR-3. In vivo, TC feeding partly prevented CAPE-induced changes in cholangiocyte apoptosis and growth and loss of ductal secretion. The protective effect of TC was associated with enhanced VEGF-A, VEGF-C, VEGFR-2 and VEGFR-3. In vitro, TC partially prevented CAPE-induced increases in apoptosis and decreases in cholangiocyte proliferation. These changes were reversed by pretreatment with VEGF-receptor inhibitors.

CONCLUSION

Manipulation of cholangiocyte VEGF expression by bile acids may be important in preventing the impairment of cholangiocyte proliferation by exogenous agents.

Therapeutic options for gastrointestinal carcinoids

Although wide surgical resection is the optimal curative therapy for carcinoid tumors, in most patients the presence of metastatic disease at diagnosis usually renders excision a palliative procedure. This nevertheless decreases tumor burden, facilitates symptom control, and prevents complications caused by bleeding, perforation, or bowel obstruction resulting from fibrosis. In the stomach (types I and II) and rectum endoscopic excision may be adequate provided the lesion(s) are local. Long-term therapy is focused on symptom alleviation and improvement of quality of life using somatostatin analogues, particularly in a subcutaneous depot formulation. In some instances interferons may have a role but their usage often is associated with substantial adverse events. Conventional chemotherapy and external radiotherapy either alone or in a variety of permutations are of minimal efficacy and should be balanced against the decrease in quality of life often engendered by such agents. Hepatic metastases may be amenable to surgery, radiofrequency ablation, or embolization either alone or in combination with chemotherapeutic agents or isotopically loaded microspheres. Rarely hepatic transplantation may be of benefit although controversy exists as to its actual use. Peptide-receptor-targeted radiotherapy for advanced disease using radiolabeled octapeptide analogs (111In/90Yt/177Lu-octreotide) appear promising but data are limited and its status remains investigational. A variety of antiangiogenesis and growth factor-targeted agents have been evaluated, but as yet have shown little promise. The keystone of current therapy remains the long-acting somatostatin analogues that alleviate symptomatology and substantially improve quality of life with minimal adverse effects.

Vascular endothelial growth factor stimulates rat cholangiocyte proliferation via an autocrine mechanism

BACKGROUND & AIMS

Vascular endothelial growth factor (VEGF) is secreted by several epithelia and modulates cellular functions by autocrine and paracrine mechanisms. The role of VEGF in cholangiocyte pathophysiology is unknown. We evaluated the role of VEGF in the regulation of cholangiocyte proliferation in rats that underwent bile duct ligation.

METHODS

The expression of VEGF-A and VEGF-C and their receptors in cholangiocytes from normal and BDL rats was evaluated. Normal or BDL rats were treated with recombinant-VEGF-A or recombinant-VEGF-C or anti-VEGF antibodies, and proliferation of cholangiocytes was evaluated in situ by morphometry and in vitro by proliferating cell nuclear antigen immunoblots and MTS assay. In vitro, normal rat cholangiocyte cultures were stimulated with r-VEGF-A or r-VEGF-C and proliferation and signal transduction were evaluated.

RESULTS

We found that (1) cholangiocytes express messenger RNA and protein for VEGF-A, VEGF-C, VEGF receptor 2 (VEGFR-2), and VEGF receptor 3 (VEGFR-3) and secrete VEGF; (2) secretion of VEGF and expression of VEGFR-2 and VEGFR-3 increases in BDL cholangiocytes; (3) blocking VEGF in vivo by anti-VEGF-A or anti-VEGF-C antibodies decreases cholangiocyte proliferation; (4) the in vivo administration of r-VEGF-A or r-VEGF-C induces cholangiocyte proliferation in normal rats; and (5) in vitro, VEGF-A increases normal rat cholangiocyte culture proliferation by activation of inositol 1,4,5-triphosphate/Ca2+/protein kinase C alpha and phosphorylation of Src/ERK1/2.

CONCLUSIONS

Cholangiocytes secrete VEGF and express VEGFR-2 and VEGFR-3, all of which are amplified in BDL cholangiocytes. VEGF induces cholangiocyte proliferation by activation of inositol 1,4,5-triphosphate/[Ca2+]i/protein kinase C alpha and phosphorylation of Src/ERK1/2. VEGF mediates the adaptive proliferative response of cholangiocytes to cholestasis.

Immunohistochemical analysis of tumor angiogenic factors in human pituitary adenomas

Microvessel density (MVD) has been studied in a number of neoplasias, and apparently, there is a relationship between angiogenesis and tumor progression, response to treatment, and outcome. In pituitary adenoma, the association between MVD and vascular endothelial growth factor (VEGF) with tumor behavior has been described, but correlation with other angiogenic factors such as fetal liver kinase 1 (Flk-1) or proliferative markers is unknown. We investigated MVD, VEGF, and its receptor Flk-1 expression in 60 human pituitary adenomas: 13 growth hormone cell adenomas, 7 prolactin cell adenomas, 5 corticotroph cell adenomas, 2 thyrotroph cell adenomas, and 33 nonfunctioning adenomas (30 gonadotroph cell adenomas and 3 null cell adenomas). We performed immunohistochemistry for CD34, Ki-67, VEGF, and Flk-1. To evaluate MVD, we used 2 methods: the number of vessels per square millimeter and the Chalkley method. Immunohistochemistry results were correlated, as well as with clinicopathologic factors. Adenomas with higher MVD were thyrotroph cell adenomas (299.9 +/- 87.5), and those with lower MVD were prolactin cell adenomas (168.6 +/- 63.3; P = .45, analysis of variance). We found a trend toward higher MVD in the adenomas of older patients (P = .142), but no difference was found regarding sex, extrasellar extension, or Ki-67 (P > .05). However, extrasellar extension was nearly significant when the Chalkley method score was high (P = .056). Low expression of VEGF was seen predominantly in prolactin cell adenomas, and high in nonfunctioning adenomas, or in cases of older patients (P < or = .032). Flk-1 score correlated with VEGF (P = .006). High expression was observed in nonfunctioning adenomas, cases presenting at older ages, and with extrasellar extension (P < or = .022). Our study shows that VEGF and Flk-1 are widely expressed in pituitary adenomas, predominantly in nonfunctioning adenomas and those presenting at older ages. Moreover, Flk-1 is associated with a more aggressive phenotype, and it may have potential therapeutic interest.