Protein expression profile of newly diagnosed acute lymphoblastic leukemia in children developing relapses.

The purpose of this investigation was to evaluate the expression profile of proteins involved in children with newly diagnosed acute lymphoblastic leukemia (ALL) children who are developing relapses. For this reason, the expressions of 10 proteins including proto-oncogene and tumor suppressor gene products, proliferative factors and resistance parameters in 104 initial cases of childhood ALL were analyzed and the proteins correlated with ALL patients who experienced relapses. Applying immunocytochemical assays, we found that 4 out of the 10 parameters revealed a relationship to developing relapses (Fisher's exact tests). These were the oncogene product Fos (p=0.002), the drug resistance proteins glutathione S-transferase (p=0.008) and P-glycoprotein (P-pg/MDR1) (p=0.07) and protein kinase C (p=0.01). By means of hierarchical cluster analysis, we were able to show that the patients could be separated according to their protein expression profile into clusters consisting of patients whose ALL relapsed later and of patients who did not show relapses in the future.

Protein expression profiles indicative for drug resistance of non-small cell lung cancer.

Data obtained from multiple sources indicate that no single mechanism can explain the resistance to chemotherapy exhibited by non-small cell lung carcinomas. The multi-factorial nature of drug resistance implies that the analysis of comprising expression profiles may predict drug resistance with higher accuracy than single gene or protein expression studies. Forty cellular parameters (drug resistance proteins, proliferative, apoptotic, and angiogenic factors, products of proto-oncogenes, and suppressor genes) were evaluated mainly by immunohistochemistry in specimens of primary non-small cell lung carcinoma of 94 patients and compared with the response of the tumours to doxorubicin in vitro. The protein expression profile of non-small cell lung carcinoma was determined by hierarchical cluster analysis and clustered image mapping. The cluster analysis revealed three different resistance profiles. The frequency of each profile was different (77, 14 and 9%, respectively). In the most frequent drug resistance profile, the resistance proteins P-glycoprotein/MDR1 (MDR1, ABCB1), thymidylate-synthetase, glutathione-S-transferase-pi, metallothionein, O6-methylguanine-DNA-methyltransferase and major vault protein/lung resistance-related protein were up-regulated. Microvessel density, the angiogenic factor vascular endothelial growth factor and its receptor FLT1, and ECGF1 as well were down-regulated. In addition, the proliferative factors proliferating cell nuclear antigen and cyclin A were reduced compared to the sensitive non-small cell lung carcinoma. In this resistance profile, FOS was up-regulated and NM23 down-regulated. In the second profile, only three resistance proteins were increased (glutathione-S-transferase-pi, O6-methylguanine-DNA-methyltransferase, major vault protein/lung resistance-related protein). The angiogenic factors were reduced. In the third profile, only five of the resistance factors were increased (MDR1, thymidylate-synthetase, glutathione-S-transferase-pi, O6-methylguanine-DNA-methyltransferase, major vault protein/lung resistance-related protein).

Vascular endothelial growth factor in newly diagnosed and recurrent childhood acute lymphoblastic leukemia as measured by real-time quantitative polymerase chain reaction.

PURPOSE: Overexpression of vascular endothelial growth factor (VEGF) is associated with increased angiogenesis, growth, and metastasis in solid tumors, but to date the significance of VEGF in leukemia has received only limited attention. Therefore, this study examined the cellular VEGF levels in 31 newly diagnosed and 22 recurrent cases of childhood acute lymphoblastic leukemia (ALL). EXPERIMENTAL DESIGN: VEGF was determined with real-time quantitative PCR methods. Kaplan-Meier statistical analyses were conducted for the relapse-free intervals and the overall survival times. The groups were compared by log-rank and rank-sum tests. RESULTS: The VEGF levels were significantly higher in recurrent ALL compared with newly diagnosed ALL (28.0 versus 3.1 units; P = 0.001). Kaplan-Meier estimates were conducted to analyze the prognostic value of VEGF levels in newly diagnosed ALL with regard to the relapse-free intervals and the overall survival times. In this analysis, the median relapse-free interval of patients with low VEGF levels was more than 10 years, whereas the relapse-free interval of patients with high VEGF expression was only 1.2 years. The median overall survival time for the collective with low VEGF levels was >10 years, whereas the survival of the group of patients with high VEGF levels was 3.9 years. This difference was not statistically significant. This may be attributable to the small number of patients involved. CONCLUSION: Our data suggest that VEGF may play an important role in the pathophysiology of ALL. The expression of VEGF raises the possibility of using angiogenesis inhibitors as a novel therapeutic strategy in childhood ALL.

Development of tumor-infiltrating lymphocytes in breast cancer after neoadjuvant paclitaxel chemotherapy.

PURPOSE: Neoadjuvant chemotherapy for breast cancer creates new possibilities for the analysis of biological factors in the tumor and/or host, which may play a role in the response to treatment. In this study we analyzed whether changes in local antitumor immunity take place after neoadjuvant paclitaxel therapy and if they correlate with response to treatment. EXPERIMENTAL DESIGN: Neoadjuvant chemotherapy (paclitaxel, 200 mg/m2 q2w, 4 treatments) was followed by definitive surgical management. Histological sections from the pre- and post-treatment surgical specimens of 25 patients were analyzed for the extent of lymphocytic infiltration and presence of tumor infiltrating lymphocytes (TILs). The cumulative apoptotic response in the tumor after the first dose of paclitaxel was also studied in 10 of 25 patients. RESULTS: Pretreatment lymphocytic infiltrate in the tumor was minimal in the majority of patients and showed no relationship with clinical response. In the patients without TILs before treatment, development of TILs after treatment was noted in 0/3 (0%) patients with stable disease, 3/12 (25%) patients with clinical partial response, and 4/6 (67%) patients with clinical complete response and pathological residual disease. These correlated with the tumor cell apoptotic response to the first dose of paclitaxel. CONCLUSIONS: These results suggest that development of TILs after treatment correlates with clinical response to neoadjuvant paclitaxel therapy. The possible mechanism(s) whereby neoadjuvant chemotherapy may lead to induction of antitumor T cells is discussed. Immunological processes may influence the response of breast cancer patients to neoadjuvant treatment.

Nonsteroidal and steroidal aromatase inhibitors in breast cancer.

Anastrozole (Arimidex), letrozole (Femara), and exemestane (Aromasin) are members of the third generation of aromatase inhibitors that has now replaced aminoglutethimide (Cytadren), the progestins, and tamoxifen (Nolvadex) as the hormonal therapy of choice in estrogen-receptor-positive, postmenopausal, metastatic breast cancer. This article will review the role of aromatase in the pathogenesis of breast cancer and the results of recent studies that have established the role of its inhibitors in estrogen-receptor-positive breast cancer. We will also briefly outline the rationale and design of ongoing studies.

Effect of highly active antiretroviral therapy on survival in patients with AIDS-associated pulmonary Kaposi's sarcoma treated with chemotherapy.

PURPOSE: Kaposi's sarcoma (KS) is the most common AIDS-related malignancy. Pulmonary involvement by KS (PKS) has carried a poor prognosis with median reported survival ranging from 3 to 10 months. We studied whether the introduction of highly active antiretroviral therapy (HAART; triple antiretroviral therapy including a protease inhibitor and two reverse transcriptase inhibitors) has been associated with improved survival for AIDS patients with PKS. PATIENTS AND METHODS: A retrospective study was performed of 37 consecutive patients with PKS and human immunodeficiency virus infection in the tumor registry at a large municipal hospital in New York City between 1994 to 1997. There were 16 patients from 1994 to 1995 (pre-HAART period) and 21 patients from 1996 to 1997 (post-HAART period). The primary end point was survival, which was defined as time from start of chemotherapy until death from any cause. RESULTS: Patients were analyzed by the date of diagnosis (pre- v post-HAART period) and whether or not they received HAART. Kaplan-Meier analysis showed significantly better survival in patients diagnosed in the post-HAART period (P =.0025). Additional Kaplan-Meier analysis indicated that patients on HAART had substantially better survival (P <.0001). Cox multivariate analyses showed that HAART therapy was associated with a reduced risk of death (hazard ratio = 0.09; 95% confidence interval, 0.03 to 0.69). CONCLUSION: In patients with AIDS-associated PKS and undergoing chemotherapy, administration of HAART was associated with increased survival.

Clinical estimation of the growth rate of lung cancer.

It is well known that the growth rate of lung tumors is closely related to prognosis and is an important determinant of responsiveness to therapy and curability. In this study, the velocity of tumor growth was calculated by dividing the area of the lesion at presentation divided by the time elapsed since symptoms were first noted. This parameter was applied to a group of patients with lung cancer and the predictive value of the velocity of tumor growth was assessed. Survival expectancy was found to be closely related to the growth rate of the tumors. The median survival time of patients with more slowly growing tumors was 102 weeks, while that of patients with fast-growing tumors was 30 weeks (log-rank test, p=0.00001). Linear regression analysis between velocity of tumor growth and tumor cell proliferation as measured by the PCNA-labelling index revealed a significant correlation between these two parameters. In conclusion, the velocity of a tumor measured in this way is an independent and significant prognostic factor for patients with lung cancer and may be used to non-invasively assess lung cancer proliferation in vivo, identifying rapidly growing tumors with poor prognosis that could benefit from a more aggressive therapy.

Cellular predictive factors for the drug response of lung cancer.

The main objective of this study to analyze which of 31 cellular factors (resistance proteins, proliferative factors, apoptotic factors, angiogenic factors, proto-oncogenes) most accurately predict the resistance of non-small cell lung carcinomas. To this purpose, we used a short-term in vitro test that measures changes in the rate at which radioactive nucleic acid precursors are incorporated into tumor cells after the addition of doxorubicin to determine the response to doxorubicin in 94 non-small cell lung carcinomas. The results obtained by the short-term test were related to the various cellular factors which were in turn determined by immunohistochemistry and flow cytometry. A significant correlation was found between the data obtained by the short-term test and the expression of P-glycoprotein 170 (P = 0.00004), glutathione-S-transferase-pi (P = 0.0002), metallothionein (P = 0.0008), thymidylate synthase (P = 0.002), O6-methylguanine-DNA-methyltransferase (P = 0.008) and lung resistance-related protein (LRP, P = 0.03). There was only a weak correlation between heat shock proteins (HSP70) and no correlation between the expression of topoisomerase II or catalase and the short-term test results. To measure the proliferative activity, the following were determined: PCNA, cyclin A, cyclin D and cdk2. Only a weak relationship was found between the expression of cdk2 (P = 0.04) and PCNA (P = 0.05) and the doxorubicin response in vitro. Of the investigated pro-apoptotic factors (Fas/CD95, Fas ligand, caspase-3), only Fas/CD95 is significantly associated with the drug response (P = 0.007). The apoptotic index also reveals a significant correlation (P = 0.03). Angiogenesis, as measured by the microvessel density and the angiogenic factors, is inversely correlated to the resistance of non-small cell lung cancer. Platelet-derived endothelial cell growth factor (PD-ECGF) and vascular endothelial growth factor (VEGF) exhibit a significant relationship to the drug resistance (P = 0.0006 and P = 0.004, respectively). Of the investigated proto-oncogenes (Fos, Jun, ErbB-1, ErbB-2, Myc, Ras), only ErbB-2 is weakly associated with the in vitro short term test. In order to determine whether combining factors can result in improved predictive information, combinations of the factors (pairs, triplets) were analyzed. The systematic investigation of these combinations yields an improvement in the predictive information. With one factor up to 76.6% of the tumors, with two factors up to 85.4% and with three factors up to 89.5% of the tumors could be correctly diagnosed.

Hypoxia-inducible factor (HIF-1) and its relationship to apoptosis and proliferation in lung cancer.

Hypoxia-inducible factor 1 (HIF-1) plays an important role in the pleiotropic response observed under hypoxia. In this study we examined whether a relationship exists between HIF-1 proteins and proliferation and apoptosis in lung cancer. To this purpose, we used immunohistochemistry to analyze HIF-1 alpha and HIF-1 beta in formalin-fixed, paraffin-embedded, non-small cell lung carcinomas (n = 96) and compared the HIF expression with cyclin A protein expression, cell cycle phases, the apoptotic index and the expression of caspase 3, Fas and Fas ligand. Additionally, we examined whether HIF-1 determinations can improve the prognostic information concerning a patient's overall survival. A relationship between HIF-1 alpha or HIF-1 beta and proliferation could not be observed. However, a significant correlation between HIF-1 expression, apoptosis and the pro-apoptotic factors caspase-3, Fas, and Fas ligand could be detected. Patients with HIF-positive carcinomas had significantly longer median survival times than patients with HIF-negative carcinomas (HIF-1 alpha: 191 vs. 60 weeks; P = 0.05; HIF-1 beta: 111 vs. 41 weeks; P = 0.003). Multivariate analyses demonstrated that the presence of HIF-1 at a given stage or extent of lymph node involvement is an independent prognostic factor for the survival of patients with non-small cell lung carcinomas.

Angiostatin expression in non-small cell lung cancer.

Angiostatin, a potent inhibitor of angiogenesis, tumor growth, and metastasis, was examined in a panel of human lung cancer cell lines with Western blot analysis and in 143 primary non-small cell lung carcinomas with immunohistochemistry. Thirty-four of 143 cases (24%) stained positively. Patients with angiostatin-positive tumors survived longer (146 weeks) than patients with angiostatin-negative tumors (77 weeks; log-rank test: P = 0.07; rank-sum test: P = 0.02). To determine whether combining stimulating and inhibiting factors might improve the prognostic capability, both angiostatin and vascular endothelial growth factor (VEGF) were analyzed together with respect to patient survival. The median survival time of patients with angiostatin-positive/VEGF-negative carcinomas was 184 weeks, whereas the median survival time of patients with angiostatin-negative/VEGF-positive tumors was only 52 weeks. The angiostatin-positive tumors exhibited an increased incidence of apoptosis and a reduced capability to be transplanted into nude mice, but these differences did not reach or were only of borderline statistical significance.

nm23-H1 expression defines a high-risk subpopulation of patients with early-stage epithelial ovarian carcinoma.

The role of the nm23 gene in human ovarian cancer is still controversial. We studied the expression of the nm23-H1 gene in 247 human epithelial ovarian carcinomas. The patients were followed-up until their death, or for a minimum of 5 years if they survived. The expression of the gene was studied by means of immunohistochemistry and a semiquantitative scoring system considering the staining intensity and the number of reactive tumour cells. Patients carrying tumours with higher expression scores (4-6 on a scale from 0 to 6) had a significantly lower survival (P = 0.01) than the rest. Further stratified statistical analysis revealed that this effect was mainly attributable to the subgroup of patients with early-stage (I and II), well- and moderately differentiated tumours. In fact, a multivariate analysis carried out for this subset of patients showed nm23-overexpression to be the only significant independent predictor of an ominous prognosis. The association of nm23-overexpression with a worse prognosis was most probably not due to mutation of the nm23 gene, since mutational analysis in 60 tumours by means of single-strand conformational polymorphism and direct sequencing disclosed only one mutation, which was located outside the open reading frame. Our results seem to indicate that nm23 expression is associated with a significantly worse prognosis in early-stage, well-differentiated epithelial ovarian carcinoma, a finding with important clinical implications, considering that many patients with ovarian cancers showing these features do not undergo any further treatment beyond surgical staging. If confirmed, they could help in tailoring the treatment of these patients in the future.

Relevance of proliferative and pro-apoptotic factors in non-small-cell lung cancer for patient survival.

This investigation first set out to analyse which cellular proliferative and apoptotic factors, in addition to the clinical prognostic factors, are most predictive in patients with non-small-cell lung carcinomas (NSCLC). To this purpose, we related the proliferative factors proliferating cell nuclear antigen (PCNA), cyclin A, cyclin D1, cyclin-dependent kinase 2 (cdk2), cdk4 and the proportion of cell cycle phases in NSCLC to the survival times of 150 patients. Additionally, we associated the expressions of Fas, Fas ligand and caspase-3 in NSCLC to patient survival. Immunohistochemistry was used to determine the proteins and flow cytometry to assess the proportion of cell cycle phases. Patients with PCNA-positive carcinomas had significantly shorter survival times than patients with PCNA-negative carcinomas (median survival times: 51 vs 89 weeks). Corresponding results were obtained with the factor cyclin A (64 vs 92 weeks), with the factor cdk2 (76 vs 89 weeks), with the factor cdk4 (62 vs 102 weeks) and with the proportion of S phases (86 vs 121 weeks). Patients with an expression of the apoptotic factors had a more favourable prognosis than patients with negative carcinomas. The median survival times of cancer patients with Fas expression was 86 weeks and of those without Fas expression only 69 weeks. Corresponding results were obtained with the Fas ligand (87 vs 41 weeks) and caspase 3 (87 vs 34 weeks). In order to determine whether a combination of factors can yield improved prognostic information, we investigated all possible combinations of the proliferative and apoptotic factors. Patients with tumours having a high proliferative activity, but which did not express apoptotic factors had the shortest survival times while patients with a low proliferative activity and a high expression of apoptotic factors had the most favourable outcome. A multivariate analysis (Cox model) of the cellular and clinical prognostic factors indicated that stage, lymph node involvement, Fas, PCNA and cyclin A are the most important prognostic factors for the clinical outcome of patients with non-small-cell lung carcinomas.

Relationship between the expression of caspase-3 and the clinical outcome of patients with non-small cell lung cancer.

This study examined whether a relationship exists between the expression of caspase-3 in 135 non-small cell lung carcinomas and clinical outcome. Immunohistochemistry and Western blot analyses were used to analyze the expression of caspase-3 in solid tumors and cell lines. A significant correlation was observed between the expression of caspase-3, survival and metastasis. Caspase-3 expression correlated with a lower incidence of lymph node involvement (p = 0.0007). The median survival was longer for patients with caspase-3 positive carcinomas than for those with caspase-3-negative tumors (41 vs 87 weeks, p = 0.038).

Paclitaxel-induced apoptosis and mitotic arrest assessed by serial fine-needle aspiration: implications for early prediction of breast cancer response to neoadjuvant treatment.

The extent of tumor reduction from neoadjuvant chemotherapy for breast cancer correlates with outcome. We investigated whether the initial cellular responses to paclitaxel are related to the extent of tumor reduction. Eleven women with breast cancer received paclitaxel (every 2 weeks for 4 cycles) as neoadjuvant treatment. Serial fine-needle aspirations (FNA; 25-gauge, 1 pass) were obtained before treatment and at 24, 48, 72, and 96 h after the first paclitaxel dose. Microscopic counts of apoptotic and mitotic indices were performed. The change in cancer volume from treatment was determined using radiological measurements with allowance for change in the histopathological amount of cancer. Apoptotic and mitotic responses usually subsided within 4 days. The duration of the initial apoptotic response was different for women with different treatment results. Cumulative apoptotic response for the first 4 days inversely correlated with the proportion of residual cancer after neoadjuvant treatment. FNA is a versatile clinical method to obtain breast cancer cells for therapy response studies. Apoptotic response to the first dose of paclitaxel is almost complete within 4 days, implying that more frequent (weekly) paclitaxel dosing might be beneficial. The apoptotic response to the first dose of paclitaxel appeared to predict the amount of cancer reduction from this treatment. This is a promising start toward the development of an early chemopredictive assay for paclitaxel treatment of breast cancer.

Association of telomerase expression with successful heterotransplantation of lung cancer.

This study analyzed whether the expression of telomerase may serve as prognostic factor for the aggressiveness of human non-small cell lung carcinomas. To this purpose the expression of telomerase measured by immunohistochemistry was compared with the take rate of the primary tumors that were heterotransplanted into nude mice. Formalin-fixed, paraffin-embedded specimens of 97 non-small cell lung carcinomas from primarily untreated patients were analyzed for the expression of telomerase by a goat polyclonal antibody (clone C-20). Moderate or strong telomerase-staining was found in 78 (80%) cases. Age, gender, stage and histology had no influence on the telomerase expression. It was discovered that of the 19 telomerase-negative carcinomas only five (26%) exhibited growth in nude mice while of the 78 telomerase-positive cases 37 (47%) were successfully transplanted. To confirm these results, alcohol-fixed, paraffin-embedded cancer specimens from another group of patients (n=58) were analyzed for telomerase expression by a rabbit polyclonal antibody (clone H-231). Corresponding results were obtained. The take rate of telomerase-negative carcinomas was only 36%; the take rate of telomerase-positive carcinomas was 59%. These data suggest that high telomerase expression does indeed correlate with the aggressiveness of non-small cell lung carcinomas.

Prognostic relevance of c-Myc and caspase-3 for patients with non-small cell lung cancer.

This analysis attempted to ascertain whether combining the expression of c-Myc and caspase-3 can improve the available prognostic information for patients with non-small cell lung carcinomas. To this purpose, the expression of c-Myc and caspase-3 was determined in 128 cases of non-small cell lung carcinoma. The median survival time for patients with c-Myc-negative carcinomas was 89 weeks; it was only 43 weeks for patients with c-Myc-positive tumors (p=0.03). The estimated increased relative risk for patients with c-Myc-positive tumors was 1.6. The median survival time for patients with caspase-3-negative carcinomas was 41 weeks while patients with caspase-3-positive carcinomas survived for 79 weeks (p=0.06). The relative risk for patients with caspase-3-negative tumors was 1.5. A significant inverse relationship between the expression of c-Myc and caspase-3 was observed (p=0.04). To determine whether the combination of c-Myc and caspase-3 expression has a higher prognostic significance, patients were grouped based on their expressions of both variables. Patients with c-Myc-negative and caspase-3-positive tumors had the most favorable prognosis (102 weeks) while c-Myc-positive and caspase-3-negative carcinomas had the most unfavorable prognosis (22 weeks; p=0.01).

Inverse correlation between apoptotic (Fas ligand, caspase-3) and angiogenic factors (VEGF, microvessel density) in squamous cell lung carcinomas.

In order to explore whether apoptosis is associated with angiogenesis in lung cancer, immunohistochemistry was employed to determine the pro-apoptotic factors Fas ligand (FasL) and caspase-3 (Cas-3) in 70 squamous cell lung carcinomas. Furthermore, the vascular endothelial growth factor (VEGF) and the microvessel density (MVD) were analyzed. The comparison between MVD and the pro-apoptotic factors demonstrated that the apoptotic factors are inversely related to MVD (Cas-3: p = 0.011, FasL: not significant). In order to confirm this result, FasL and Cas-3 were also compared with the expression of VEGF. Again, an inverse correlation between VEGF and the pro-apoptotic factors was found (Cas-3: p = 0.019, FasL: p = 0.008). The inverse correlation between angiogenesis and apoptosis may be explained by the activation of pro-apoptotic and anti-angiogenic factors caused by hypoxia.

Xenotransplantability of human squamous cell lung cancer in nude mice is not affected by angiogenic factors.

Sixty-two human squamous cell lung carcinomas were analyzed for expression of various angiogenic growth factors and their receptors using immunohistochemistry. The data were correlated with xenotransplantability of these tumors in nude mice. None of the factors investigated did show an association with xenotransplantability. However, there was a trend that specimens lacking VEGF165 were established as xenografts at a higher incidence (52%) than those expressing VEGF165 (39%).

Association of cyclin D1 expression in lung cancer and the smoking habits of patients.

This study examined whether or not cyclin D1 expression is associated with the smoking habits of patients with non-small cell lung carcinomas (NSCLC). Immunohistochemistry was used to analyze 181 NSCLC samples for the expression of cyclin D1. Expression of cyclin D1 protein was found in 130 out of 181 cases (72%). A significant relationship between cyclin D1 expression and stage or histological classification was not observed. The carcinomas of smokers expressed cyclin D1 in 77% of the cases while carcinomas of non-smokers expressed this protein only 57% of the time (P < 0.01, Fisher's exact test). The correlation between smoking and cyclin D1 expression was maintained when the analysis was limited to squamous cell lung carcinomas. However, no correlation was found between cyclin D1 expression and the smoking habits of patients with adenocarcinomas. This can be explained by the fact that the development of adenocarcinomas--in contrast to squamous cell lung carcinomas--is not closely related to tobacco smoke.

Biological characterization of subgroups of squamous cell lung carcinomas.

Recently, Pezzella et al. (Am. J. Pathol., 1997, 151: 1417-1423, 1997) reported on a subgroup of non-small cell lung carcinomas that had no morphological evidence of neoangiogenesis but appeared to grow and were highly aggressive. In this investigation, we subdivided 87 squamous cell lung carcinomas into four subgroups according to angiogenesis (low and high vessel density) and tumor growth (low and high tumor cell proliferation). The aim was to find differences, if any, in the angiogenic status and clinical behavior between these subgroups. We identified a group of tumors with low angiogenesis and high tumor cell proliferation that was characterized by high expression of vascular endothelial growth factor, low expression of basic fibroblast growth factor, reduced apoptosis, increased incidence of metastases, and short survival times. These data show that even squamous cell lung carcinomas are a heterogeneous group of tumors that can be subdivided in tumors with different biological properties and different clinical behaviors.