Management of surgical diseases of thyroid gland indications of the United Italian Society of Endocrine Surgery (SIUEC).

A task force of the United Italian society of Endocrine Surgery (SIUEC) was commissioned to review the position statement on diagnostic, therapeutic and health­care management protocol in thyroid surgery published in 2016, at the light of new technologies, recent oncological concepts, and tailored approaches. The objective of this publication was to support surgeons with modern rational protocols of treatment that can be shared by health-care professionals, taking into account important clinical, healthcare and therapeutic aspects, as well as potential sequelae and complications. The task force consists of 13 members of the SIUEC highly trained and experienced in thyroid surgery. The main topics concern clinical evaluation and preoperative workup, patient preparation for surgery, surgical treatment, non-surgical options, postoperative management, prevention and management of major complications, outpatient care and follow-up.

Hemithyroidectomy versus total thyroidectomy in the intermediate-risk differentiated thyroid cancer: the Italian Societies of Endocrine Surgeons and Surgical Oncology Multicentric Study.

The surgical treatment of the intermediate-risk DTC (1-4 cm) remains still controversial. We analyzed the current practice in Italy regarding the surgical management of intermediate-risk unilateral DTC to evaluate risk factors for recurrence and to identify a group of patients to whom propose a total thyroidectomy (TT) vs. hemithyroidectomy (HT). Among 1896 patients operated for thyroid cancer between January 2017 and December 2019, we evaluated 564 (29.7%) patients with unilateral intermediate-risk DTC (1-4 cm) without contralateral nodular lesions on the preoperative exams, chronic autoimmune thyroiditis, familiarity or radiance exposure. Data were collected retrospectively from the clinical register from 16 referral centers. The patients were followed for at least 14 months (median time 29.21 months). In our cohort 499 patients (88.4%) underwent total thyroidectomy whereas 65 patients (11.6%) underwent hemithyroidectomy. 151 (26.8%) patients had a multifocal DTC of whom 57 (10.1%) were bilateral. 21/66 (32.3%) patients were reoperated within 2 months from the first intervention (completion thyroidectomy). Three patients (3/564) developed regional lymph node recurrence 2 years after surgery and required a lymph nodal neck dissection. The single factor related to the risk of reoperation was the histological diameter (HR = 1.05 (1.00-1-09), p = 0.026). Risk stratification is the key to differentiating treatment options and achieving better outcomes. According to the present study, tumor diameter is a strong predictive risk factor to proper choose initial surgical management for intermediate-risk DTC.

Thyroid ultrasonography reporting: consensus of Italian Thyroid Association (AIT), Italian Society of Endocrinology (SIE), Italian Society of Ultrasonography in Medicine and Biology (SIUMB) and Ultrasound Chapter of Italian Society of Medical Radiology (SIRM).

Thyroid ultrasonography (US) is the gold standard for thyroid imaging and its widespread use is due to an optimal spatial resolution for superficial anatomic structures, a low cost and the lack of health risks. Thyroid US is a pivotal tool for the diagnosis and follow-up of autoimmune thyroid diseases, for assessing nodule size and echostructure and defining the risk of malignancy in thyroid nodules. The main limitation of US is the poor reproducibility, due to the variable experience of the operators and the different performance and settings of the equipments. Aim of this consensus statement is to standardize the report of thyroid US through the definition of common minimum requirements and a correct terminology. US patterns of autoimmune thyroid diseases are defined. US signs of malignancy in thyroid nodules are classified and scored in each nodule. We also propose a simplified nodule risk stratification, based on the predictive value of each US sign, classified and scored according to the strength of association with malignancy, but also to the estimated reproducibility among different operators.

Fibrous Variant of Hashimoto's Thyroiditis as a Diagnostic Pitfall in Thyroid Pathology.

Fibrous variant of Hashimoto's thyroiditis is a rare condition occurring in about 10% cases, mainly middle age people. It is characterized by an extensive fibrous proliferation without extension into the surrounding structures. A 55-year-old female was referred to our department for an unexplained onset of cervical discomfort. She presented a voluminous goiter of hard consistence, dyspnea and dysphagia. Given the compressive symptoms and the non-diagnostic result of the biopsy, a total thyroidectomy was performed. Microscopically the thyroid parenchyma was characterized by broad bands of fibrosis with severe atrophy of thyroid follicles and lymphocytic inflammatory infiltrate distributed within and around the lobules. In view of the morphological and immunohistochemical findings, a diagnosis of HTFV was made. The fibrosclerotic process is the key feature of several thyroid diseases so that the clinician and the pathologist have to consider that many diagnostic pitfalls can occur in this field. The differential diagnosis between HTFV and RD is sometimes arduous due to the partial clinical and morphological overlapping and to the poor efficacy of conventional cytology as well as pre-surgical biopsy. Considering these features, histological examination is mostly mandatory.

Thyroid nodules treated with percutaneous radiofrequency thermal ablation: a comparative study.

PURPOSE: Percutaneous radiofrequency thermal ablation (RTA) was reported as an effective tool for the management of thyroid nodules (TNs). The aim of this study was to investigate the effects of RTA and to establish whether they were treatment-related by comparison with a matched, untreated control group. PATIENTS AND METHODS: The study population included 40 patients with compressive TNs: 22 had nontoxic TNs, and 18 had toxic TNs and were treated with methimazole. In all patients, a fine-needle aspiration cytology was performed to exclude a thyroid malignancy. STUDY DESIGN: Twenty patients were treated with RTA (group A), and 20 others did not receive any treatment (group B). At baseline, age, gender, and TN features did not differ significantly between groups. All patients were clinically, biochemically, and morphologically evaluated at baseline and after 1, 3, 6, and 12 months. RESULTS: TN volume significantly decreased in group A (1.8 ± 0.3 ml at 12 months vs. 13.3 ± 1.8 ml at baseline; P < 0.0001) and remained stable in group B [11.7 ± 1.5 ml at 12 months vs. 11.2 ± 1.5 ml at baseline; P = not significant (NS)]. At 3-, 6-, and 12-month evaluations, TN volume was significantly lower in group A than in group B (P < 0.005). At the end of the follow-up, pressure symptoms were improved in all patients in group A but persisted unchanged in group B. In group A, hyperthyroidism completely recovered in 40% and improved in 40% of patients with toxic TNs, whereas it persisted in all patients with toxic TNs in group B. RTA was safe and well tolerated in all patients. CONCLUSIONS: RTA induced a marked TN volume shrinkage resulting in parallel improvement of pressure symptoms. In most patients with toxic TNs, hyperthyroidism significantly improved as well. RTA may represent a valid therapeutic approach in patients with TNs not receiving conventional treatments.

Ischemic steal syndrome in a hemodialysis patient: The roles of Doppler ultrasonography and dynamic Doppler studies in diagnosis and treatment selection.

Ischemic steal syndrome (ISS) is a complication that can occur after the construction of a vascular access for hemodialysis. It is characterized by ischemia of the hand caused by marked reduction or reversal of flow through the arterial segment distal to the arteriovenous fistula (AVF). The diagnosis of hand ischemia is based on physical examination, but imaging studies are very useful for detecting the true cause of ischemia and for selecting an appropriate therapeutic strategy. In this report, we describe an uncommon cause of ISS in a patient on hemodialysis. The ischemia was caused by the presence of undetected flow through an older AVF on the same arm as the AVF used for dialysis. The unsuspected "steal" was disclosed by color Doppler examination of the vascular bed of the patient's left arm. Dynamic Doppler studies then played a fundamental role in the decision to ligate the distal radio-cephalic AVF. The procedure led to the complete relief of ischemic symptoms.

Wound complications after kidney transplantation in nondiabetic patients.

INTRODUCTION: Impaired wound healing represents a common operative complication after kidney transplantation. This problem seems to be affected by factors related to surgical technique, drugs, and patient/graft peculiarities. PATIENTS AND METHODS: From January 2000 to December 2007, 350 consecutive kidney transplantations were performed in a population of nondiabetic patients. We evaluated the influence of various factors on impaired wound healing. RESULTS: Among 350 kidney transplantation patients, we observed 54 cases (15.43%) of impaired healing of the surgical incision: 36 (10.29%) with first level and 18 (5.14%) with second level wound complications. Factors related to complications were overweight and delayed graft function. Cyclosporine and tacrolimus had similar effects. However, all patients developing second level complications showed more risk factors. In our experience, postoperative lymphocele did not occur as an unique factor but became a significant risk factor when associated with another one. Patients who did not have reconstruction of the muscle layers showed a greater incidence of incisional complications. CONCLUSION: Impaired healing of the surgical incision more or less seriously influenced outcomes of transplanted patients. This complication was common and usually related to the presence of more than one risk factor.

Healing of surgical incision in kidney transplantation: a single transplant center's experience.

INTRODUCTION: Impaired healing of the surgical incision represents a common complication after kidney transplantation. We led a retrospective study seeking to understand the factors linked to these complications and reasons for their reduction during the last year. PATIENTS AND METHODS: From January 2000 to April 2004, 170 consecutive kidney transplantations were performed in a homogenous patient population. We evaluated the influence of following factors to determine impaired healing of the incision: antirejection drugs, overweight/obesity, age, delayed graft function (DGF), diabetes, and abdominal wall reconstruction technique. RESULTS: Among 165 patients we observed 26 (15.76%) cases of impaired healing of the surgical incision: 17 (65,38%) with first-level and nine with second-level wound complications. CONCLUSIONS: Impaired healing of the surgical incision influences the outcome of kidney transplant patients. In our study we observed that cyclosporine and tacrolimus similary affected the incision's healing. It was not possible to evaluate the role of basiliximab. A univariate analysis of the factors related to complications revealed overweight and DGF. However, all patients developing second-level complications showed more risk factors. Patients who had not had reconstruction of the muscle layers showed a greater incidence of surgical complications, whereas patients who had skin sutured with an intradermic technique did not show an increased risk.

Transplantation and young surgeons in Italy.

The relation between young surgeons and transplantation has always been a "love and hate" one. Until a few years ago this branch of surgery was seen as pioneering, with extreme and and extensive training, and was reserved to few elected members. Nowadays things are different. In this article we try to understand the true reasons that young Italian surgeons avoid transplantation surgery.

Circulating insulin-like growth factor-I levels are correlated with the atherosclerotic profile in healthy subjects independently of age.

To investigate the relationships between the GH-IGF-I axis and the atherosclerotic profile, we designed this open, observational, prospective study. Peak GH after GHRH+arginine (ARG) test, serum IGF-I and IGF binding protein-3 (IGFBP-3), lipid profile, homeostasis model assessment (HOMA) index and intima-media thickness (IMT) at common carotid arteries were measured in 174 healthy individuals (92 women, 82 men, aged 18-80 yr). Exclusion criteria for this study were: 1) body mass index (BMI) > or = 30 kg/m2; 2) personal history of cardiovascular diseases; 3) previous or current treatments of diabetes or hypertension; 4) previous corticosteroids treatment for longer than 2 weeks or estrogens for longer than 3 months; 5) smoking of more than 15 cigarettes/day and alcohol abuse. Subjects were divided according to age in decade groups from < 20 to > 70 yr. BMI increased with age, as did systolic and diastolic blood pressures, although they remained in the normal range. The GH peak after GHRH+ARG test was significantly higher in the subjects aged < 20 yr than in all the other groups (p < 0.01), but was similar in the remaining groups. An inverse correlation was found between the IGF-I z-score and total/HDL-cholesterol ratio (p = 0.02) and mean IMT (p = 0.0009); IGFBP-3 z-score and mean IMT (p = 0.043); IGF: IGFBP-3 molar ratio and total/HDL-cholesterol ratio (p < 0.0001) and mean IMT (p < 0.0001). Atherosclerotic plaques were found in 7 out of 12 subjects (53.8%) with a z-IGF-I score from < or = -2 to -1, in 4 out of 63 (6.3%) with a z-IGF-I score from -0.99 to 0.1 out of 66 (1.5%) with a z-IGF-I score from 0.1 to 1 and none of the 33 subjects with an IGF-I z-score >1 (p = 0.006). At multi-step regression analysis, age was the best predictor of HDL-cholesterol levels and mean IMT, IGF-I level was the best predictor of total cholesterol and total/HDL-cholesterol ratio, the IGF-I/IGFBP-3 molar ratio was the best predictor of triglycerides levels. The z-scores of IGF-I and IGFBP-3 were the second best predictors of mean IMT after age. In conclusion, IGF-I and IGFBP-3 were negatively correlated with common cardiovascular risk factors, studied as total/HDL-cholesterol ratio, and/or early atherosclerosis, studied as IMT at common carotid arteries. The prevalence of atherosclerotic plaques, though not hemodinamically significant, was higher in the subjects having a z-score of IGF-I of < or = -2 to -1. Our results support a role of the IGF/IGFBP-3 axis in the pathogenesis of atherosclerosis.

Increased arterial intima-media thickness by B-M mode echodoppler ultrasonography in acromegaly.

BACKGROUND: Patients with acromegaly have an increased morbidity and mortality for cardiovascular diseases. Despite the increasing evidence for the existence of a specific cardiomyopathy in acromegaly, the presence of vascular abnormalities has been never investigated. OBJECTIVE: To evaluate the cardiovascular risk and premature atherosclerosis in acromegaly. SUBJECTS: Forty-five patients with acromegaly and 30 sex- and age-matched healthy subjects were included in this study: 30 patients were studied at the diagnosis of acromegaly and were in active disease (GH 59.3 +/- 10.2 mU/l, IGF-I 733 +/- 57.6 microg/l) while 15 patients were studied after surgery and/or radiotherapy and were cured from the disease (GH 4.5 +/- 0.7 mU/l, IGF-I 172.4 +/- 16.9 microg/l). METHODS: Body mass index (BMI), systolic (SBP) and diastolic blood pressure (DBP), serum total, LDL- and HDL-cholesterol, triglycerides, and fibrinogen levels, prothrombin time (PT), activated partial thromboplastin time (APTT), glucose and insulin levels (fasting and after glucose load) were measured in all patients and controls. By echodoppler ultrasonography, blood systolic (SPV) and diastolic (DPV) peak velocity, and resistance index (RI) were measured at both common and internal carotid arteries where presence, size and location of atherosclerotic plaques were evaluated by B-Mode ultrasonography. Intima-media thickness (IMT) of both common carotids was measured by M-Mode ultrasonography. RESULTS: SBP, but not DBP, was significantly higher in patients with active disease than in cured patients and controls (P = 0.003). Hypertension was found in nine (30%) patients with active disease, in two (13.3%) of those cured from acromegaly and in none of controls (chi2 = 10.81, P < 0.004). Fasting blood glucose levels were significantly higher both in patients with active disease and in those cured from the disease than in controls (P < 0.001). Circulating insulin levels were significantly higher in patients with active disease than in cured patients and controls (P < 0.001) and in cured patients than in controls (P < 0.001). Glucose tolerance abnormalities were found in 13 (43.3%) patients with active disease, in four (26.6%) patients with inactive disease and in four controls (13.3%) (chi2 = 6.71, P = 0.03). Total blood cholesterol levels were similar in the three groups, LDL-cholesterol and triglycerides levels were significantly higher, whereas HDL-cholesterol levels were significantly lower both in patients with active disease and in those cured from the disease than in controls (P < 0.001). Serum fibrinogen levels were significantly higher both in patients with active disease and in those cured from the disease than in controls (P < 0.001). No difference was found in PT and APTT levels among the three groups. At the level of right and left common carotid arteries, IMT was significantly higher both in patients with active disease and in those cured from the disease than in controls (P < 0.001). Both right and left SPV, but not DPV, were significantly higher in patients with active disease than in those cured from the disease and in controls (P < 0.01). Well defined carotid wall plaques were detected in two patients (6.6%) with active disease, in one patient cured from the disease (6.6%) and in two controls (6.6%). At the level of right and left internal carotid arteries, SPV, DPV and RI were similar among the three groups. Well defined carotid wall plaques were detected in three patients with active disease (10%), two patients cured from the disease (13.3%) and in one control (3.3%). CONCLUSIONS: A significant increase of IMT of both common carotid arteries was observed in patients with active acromegaly, this was also found in those cured from acromegaly. However, the prevalence of well defined carotid plaques was not increased in both groups of patients with acromegaly as compared to controls. On this basis, heart more than vessels seems to be affected by chronic GH and IGF-I excess in acromegaly.

Analysis of color Doppler signal intensity variation after levovist injection: a new approach to the diagnosis of thyroid nodules.

The objective of this study was to evaluate the usefulness of a galactose-based ultrasonographic contrast agent, Levovist (Schering AG, Berlin, Germany), in differentiating benign from malignant thyroid nodules by analysis of the time-intensity curves correlating the variation of the intensity signal value during the contrast transit time. Fifty-four patients scheduled for surgical removal of a nodule or the thyroid gland or both after cytologic examination were enrolled in this study; all of the nodules underwent a baseline color and power Doppler evaluation and then to a color Doppler examination after an intravenous bolus injection of Levovist. The time-intensity curves were analyzed with respect to the histologic results. Carcinomas showed a significantly earlier arrival time of Levovist than nodular hyperplastic benign nodules and adenomas (8.1 +/- 1.41 versus 19.6 +/- 2.2 and 16.1 +/- 2.8 seconds; P < .0001), although no significant difference occurred between hyperplastic benign nodules and adenomas; carcinomas and adenomas showed an earlier time to peak than hyperplastic benign nodules (14.6 +/- 1.2 and 23.1 +/- 3.8 versus 33.0 +/- 3.0 seconds; P < .0001). No significant difference was found in baseline, peak, final intensity signal, and percent variation of intensity signal among hyperplastic benign nodules, adenomas, and carcinomas. Although cytologic examination still remains the standard of reference for the presurgical diagnosis of thyroid nodules, the preliminary data of this pilot study demonstrate that the analysis of time-intensity curves after Levovist injection might provide useful, complementary, and quantitative information to differentiate benign from malignant thyroid nodules.

Effect of two years of growth hormone and insulin-like growth factor-I suppression on prostate diseases in acromegalic patients.

The insulin-like growth factors (IGFs) have mitogenic effects on normal and tumoral prostate epithelial cells and have been suggested to be involved in prostate cancer. Moreover, chronic GH and IGF-I excess causes prostate overgrowth in patients with acromegaly. This study was designed to investigate whether the suppression of GH and IGF-I levels by surgery or pharmacotherapy could induce the regression of prostatic hyperplasia in acromegalic patients. To this end, prostate volume (PV) as well as the occurrence of prostatic diseases were studied by transrectal ultrasonography in 23 untreated acromegalic patients (with elevated GH and IGF levels). None of the patients reported symptoms due to prostatic disorders or obstruction. At study entry, prostate hyperplasia was found in half patients. After 2 yr, GH, IGF-I, and IGFBP-3 levels were decreased, whereas prostate-specific antigen levels did not change. PV was decreased in the 16 patients who were well controlled. Among the 6 patients with prostate hyperplasia at study entry who achieved disease control, 4 regained a normal PV at the end of the 2 yr of treatment, whereas none of the 5 patients with prostate hyperplasia at study entry and not achieving disease control normalized their PV. When patients were divided according to age, prostate volume decreased after 2 yr only in the 8 controlled patients aged below 50 yr, but not in those controlled and with age above 50 yr despite similar decrease in GH, IGF-I, and IGFBP3 levels. No clinical, transrectal ultrasonography, or cytological evidence of prostate cancer was detected during the study period. These data suggest that hyperplasia, but not cancer, is frequent in acromegalic men, and that the GH-IGF axis and age are independently associated with the development of this process.

Effect of GH and/or testosterone deficiency on the prostate: an ultrasonographic and endocrine study in GH-deficient adult patients.

BACKGROUND: The role of IGF-I in prostate development is currently under thorough investigation since it has been claimed that IGF-I is a positive predictor of prostate cancer. OBJECTIVE: To investigate the effect of chronic GH and IGF-I deficiency alone or associated with testosterone deficiency on prostate pathophysiology in a series of patients with hypopituitarism. DESIGN: Pituitary, androgen and prostate hormonal assessments and transrectal prostate ultrasonography (TRUS) were performed in 30 men with adulthood onset GH deficiency (GHD) and 30 age-matched healthy controls, free from previous or concomitant prostate disorders. RESULTS: Plasma IGF-I levels were significantly lower in GHD patients than in controls (Pearson's coefficient P<0.0001). At study entry, 6 of the 13 hypogonadal patients and 7 of the 17 eugonadal patients had plasma IGF-I below the age-adjusted normal range. At study entry, testosterone levels were low in 13 patients (mean +/-s.e.m., 3.8+/-1.0 nmol/l) while they were normal in the remaining 17 (19.4+/-1.4 nmol/l). No difference in prostate-specific antigen (PSA), and PSA density was found between GHD patients (either hypo- or eugonadal) and controls, while free PSA levels were significantly higher in eugonadal GHD than in controls (0.4+/-0.04 vs 0.2+/-0.03 microg/l; P<0.01). No difference in antero-posterior prostate diameter and transitional zone volume (TZV) was observed among groups, while both transverse and cranio-caudal diameters were significantly lower in hypogonadal (P<0.01) and eugonadal GHD patients (P<0.05) than in controls. Prostate volume (PV) was significantly lower in hypogonadal GHD patients (18.2+/-3.0 ml) and eugonadal GHD patients (22.3+/-1.6 ml), than in controls (25.7+/-1.4, P<0.05). The prevalence of prostate hyperplasia (PV>30 ml) was significantly lower in hypogonadal and eugonadal GHD patients, without any difference between them (15.3% and 5.8%), than in controls (43.3%) (chi(2)=6.90, P=0.005). No difference was found in PV between patients with normal or deficient IGF-I levels both in the hypogonadal group (19. 9+/-4.7 vs 17.3+/-4.0 ml) and in the eugonadal group (22.6+/-2.3 vs 21.8+/-2.5 ml). When controls and patients were divided according to age (<60 years and >60 years), PV was significantly lower in hypogonadal GHD patients aged below 60 years than in age-matched controls (P<0.01) or eugonadal GHD patients (P<0.01), without any difference between controls and eugonadal GHD patients. Controls aged above 60 years had significantly higher PV than both hypogonadal and eugonadal GHD patients (P<0.01). Calcifications, cysts or nodules were found in 56.7% of patients and in 50% of controls (chi(2)=0.067, P=0.79). In controls, but not in GHD patients, PV and TZV were correlated with age (r=0.82, r=0.46, P<0. 0001 and P<0.01 respectively). PV was also correlated with GH (r=-0. 52, P=0.0026), IGF-I (r=-0.62, P=0.0002) and IGF-binding protein 3 (IGFBP-3) levels (r=-0.39, P=0.032) but neither with testosterone or dihydrotestosterone (DHT) levels. In GHD patients TZV but not PV was correlated with age (r=0.58, P=0.0007) and neither TZV nor PV were correlated with GH, IGF-I or IGFBP-3 levels. CONCLUSIONS: Chronic GH deficiency in adulthood causes a decrease in prostate size, mostly in patients with concomitant androgen deficiency and age below 60 years, without significant changes in the prevalence of structural prostate abnormalities.

Power Doppler ultrasonographic assistance in percutaneous ethanol injection of autonomously functioning thyroid nodules.

The purpose of this study was to explore the potential role of power Doppler sonography in guiding percutaneous ethanol injection of autonomously functioning thyroid nodules. Thirty-two patients with pretoxic adenoma and 15 with toxic adenoma underwent percutaneous ethanol injection under power Doppler sonographic guidance. All patients with pretoxic adenoma and 13 of 15 patients with toxic adenoma were treated successfully (normalization of circulating thyroid hormones and thyroid stimulating hormone levels and disappearance of nodular hyperactivity with complete recovery of extranodular tracer uptake at scintigraphy). Power Doppler sonography showed the progressive reduction of the intranodular blood flow until its extinction after 6 to 12 months. Nodular shrinkage was obtained in all patients (from 10.85 +/-1.04 to 2.9 +/- 0.3 ml in pretoxic adenoma and from 15.4 +/- 1.8 to 4.2 +/- 0.7 ml in toxic adenoma. Power Doppler sonographic guidance seems to improve the outcome of percutaneous ethanol injection, allowing detection of blood flow even in very small vessels, permitting the ethanol to be guided toward the main afferent vessels of the nodules, and making it possible to monitor the diffusion and the effects of ethanol on nodular vascularization.

Key role of the cyclin-dependent kinase inhibitor p27kip1 for embryonal carcinoma cell survival and differentiation.

Hexamethylen-bisacetamide (HMBA) represents the prototype of a group of hybrid polar compounds, which induce differentiation in a variety of transformed cells including human embryonal carcinoma cells. Therefore, HMBA has been used in the differentiation therapy of cancer for patients with both hematological and solid malignancies. Upon HMBA treatment, the embryonal carcinoma cell line NTERA-2 clone D1 (NT2/D1) accumulates in G1 and undergoes terminal differentiation. Here we demonstrate that growth arrest and differentiation of NT2/D1 cells induced by HMBA involve increased expression of the cyclin-dependent kinase inhibitor p27, enhanced association of p27 with cyclin E/CDK2 complexes and suppression of kinase activity associated to cyclin E/CDK2 (but not to cyclin D3/CDK4). When HMBA differentiation was induced in the presence of p27 antisense oligonucleotides, NT2/D1 cells failed to arrest growth properly and, in parallel with the reduction of the anti-apoptotic Bcl-2 gene expression, cells underwent massive programmed cell death. Conversely, constitutive expression of p27 into NT2/D1 cells induced a marked reduction in the growth potential of these cells and partially reproduced HMBA-induced modification of surface antigen expression (down-regulation of SSEA-3 expression and up-regulation of VINIS-53 expression). Expression of p21 induced growth arrest but not differentiation. Likewise, inhibition of CDK2 by transfection of a dominant negative CDK2 in NT2/D1 cells or treatment with the kinase inhibitor olomucine induced growth arrest but not differentiation. Therefore, we propose that p27 represents a crucial molecule in HMBA signaling that cannot be replaced by p21. Furthermore, the results obtained with CDK2 inhibitors demonstrate that the block of CDK2 activity is sufficient for growth arrest but not for cell differentiation and suggest that, at least in these cells, growth arrest and differentiation are regulated by two overlapping but different pathways.