A PATIENT WITH AN ATYPIC NECK MASS LESION.

An 81-year-old woman presented with a history of essential hypertension for eight years and an asymptomatic multinodular goiter that had been incidentally discovered on neck ultrasonography two years ago and an-isohypoechoic mass lesion located adjacent to the right lobe inferior pole of the thyroid gland. Parathyroid adenoma or lymphadenopathy were the differential diagnosis. After two years, the endocrine surgeon decided to operate her multinodular goiter and her probably benign lesion. Intraoperatively, the blood pressure and pulse rate increased markedly and intravenous antihypertensive treatment was administered. She was discharged after blood pressure control. A 2 mm micromedullary thyroid carcinoma with C-cell hyperplasia located on the left lobe of the thyroid was detected. The aforementioned mass lesion was also reported as typical cervical paraganglioma. Because of concomitant medullary thyroid carcinoma with C-cell hyperplasia and paraganglioma the patient was subjected to genetic counseling and molecular testing for hereditary cancer syndromes. A variation of the succinate dehydrogenase gene D (SDHD) NM_003002.3: c.325C> T (Gln109Term) has been reported as the disease-causing mutation. Herein we present a case diagnosed for neck paraganglioma and medullary thyroid carcinoma after an intraoperative hypertensive crisis.

A histological assessment of the Bethesda system for reporting thyroid cytopathology (2010) abnormal categories: a series of 219 consecutive cases.

OBJECTIVE: The purposes of this study were to establish the distribution of thyroid lesions that were seen in Hatay (a province of southern Turkey), to review the accuracy of fine needle aspiration cytology (FNAC) in the diagnosis of thyroid nodules and to correlate the FNAC results with the histopathology of the excised specimens, especially in indeterminate cases. METHODS: Data on patient cytology were retrieved by a retrospective search of all thyroid FNAC specimens that had been evaluated at the Department of Pathology, Antakya Public Hospital, Hatay, Turkey between January 2009 and February 2011; 1021 thyroid FNAC samples were reviewed and interpretations were recorded according to the Bethesda system for reporting thyroid cytopathology (TBSRTC). The results of adequate FNAC samples were compared with the histological diagnoses in the cases in which surgery was performed, and the malignancy rates, especially in indeterminate categories, were calculated. RESULTS: Of the 1021 FNAC samples, 697 (68.3%) were benign, 122 (11.9%) were non-diagnostic, 100 (9.8%) were atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS), 41 (4%) were follicular neoplasm/suspicious for follicular neoplasm (FN/SFN), 36 (3.5%) were suspicious for malignancy (SM) and 25 (2.4%) were malignant. In 219 cases, there was follow-up histology. Rates of malignancy were as follows: benign, 0%; AUS/FLUS, 12.7%; FN/SFN, 35.0%; SM, 91.4%; malignant, 100%. CONCLUSIONS: In our study, the cytohistological correlation of benign and malignant lesions was 100%. In the indeterminate categories, we recommend that clinicians should evaluate both the clinical and radiological findings of patients in addition to the FNAC results.

Early changes in carcinogenesis of colorectal adenomas.

OBJECTIVES: Adenocarcinoma of the colon and rectum is the third most common cause of cancer deaths and the sixth most common cancer in the world. Adenomas are benign neoplastic lesions which can be transformed into carcinomas, but this is usually not the case. There should be some risk factors which lead to the development of carcinomas into adenomas. The aim of this study is to find out the early changes and high risk factors related to carcinogenesis in colonic polyps. METHODS: In this study, we reviewed nearly 1000 colonoscopic biopsies and chose 72 biopsies. We developed three groups (tubular adenomas group 1, villous adenomas group 2, normal mucosa group 3); each group had 24 different biopsies. P53, Ki-67, bcl-2, cyclin D1, E-cadherin, c-erb B2 immunohistochemistry and human papillomavirus (HPV) in-situ hybridization were used for analysis. RESULTS: Five of the seventy-two cases were positive in HPV in-situ analysis. Four of them were villous adenomas and one was a tubular adenoma. Ki-67 expression was limited only to crypts in group 3 but in groups 1 and 2, Ki-67 expression was seen both in crypt epithelium and surface epithelium. Cyclin D1, c-erb B2, bcl-2 expression was significantly increased in neoplastic polyps. CONCLUSION: Ki-67 expression, both in the crypt and surface epithelium, and cyclin D1, c-erb B2, bcl-2 over-expression may be a clue of dysplastic epithelium and if the role of HPV is elucidated and shown to be important in colonic carcinogenesis, then vaccination might prevent carcinogenesis caused by HPV.

Diagnostic pitfalls in the evaluation of fine needle aspiration cytology of the thyroid: correlation with histopathology in 260 cases.

OBJECTIVES: Fine needle aspiration cytology (FNAC) of the thyroid is a non-invasive, cost-effective screening procedure that is valuable for distinguishing neoplastic lesions from non-neoplastic nodules. The aim of this study was to determine the diagnostic accuracy of FNACs performed at our institution by correlating FNAC results with histopathological diagnoses. METHODS: Two hundred and seventy-one aspiration cytology specimens followed by thyroidectomy were included in the study, and the results of 260 adequate FNACs were compared with their histological diagnoses. RESULTS: The sensitivity and specificity of thyroid FNAC for detecting neoplasia were 92.6% and 91.6%, respectively. There were 15 (5.7%) false positives and six (2.3%) false negatives. CONCLUSIONS: The results showed that follicular cells that exhibit some of the features of papillary carcinoma could be observed in a cytology slide of Hashimoto's thyroiditis, leading to a diagnostic pitfall. In addition, cellularity and overlapping cytological criteria in hyperplasia might lead to a false diagnosis.

Relevant histopathologic findings that distinguish acute cellular rejection from cholangitis in hepatic allograft biopsy specimens.

BACKGROUND AND AIM: Histopathologic differential diagnosis of acute cellular rejection (ACR) and cholangitis continue to pose important problems following liver transplantation. The purpose of the present study was to evaluate the histopathologic features of ACR versus cholangitis. METHODS: The following variables were evaluated among 36 hepatic allograft biopsy specimens, consisting of 21 with ACR (group 1) and 15 with cholangitis (group 2) for ductal neutrophilic infiltration, presence/density of portal eosinophilia, centrilobular necrosis, central/portal vein endothelialitis, pericentral inflammation, hepatocyte ballooning, hepatocanalicular/ductular cholestasis, hepatocyte apoptosis, lobular inflammation, ductular proliferation, periductal fibrosis/edema, ductular epithelial damage, and portal inflammation. Only the first biopsy samples of the ACR group were included in this study. RESULTS: The incidences of ductal neutrophilic infiltration (93.3% vs 19%), hepatocanalicular cholestasis (86.7% vs 47.6%), ductular cholestasis (60% vs 0%), ductular proliferation (93.3% vs 4.8%), and periductal fibrosis/edema (93.3% vs 19%) were significantly greater in group 2 than group 1 (P < .05). In contrasts the incidences of portal eosinophilia (mean +/- SD, 3.37 +/- 3.9 vs 0.73 +/- 0.8), dense portal eosinophilia (mean +/- SD, 0.33 +/- 0.31 vs 0.11 +/- 0.16), central vein endothelialitis (0% vs 57.1%), portal vein endothelialitis (20% vs 95.2%), apoptosis (40% vs 71.4%), and necroinflammation (0% vs 90.5%) were significantly higher in group 1 (P < .05). The other parenchymal histopathologic changes and features of portal inflammation were similar in the 2 groups. CONCLUSION: In the differential diagnosis, ductal changes (cholestasis, neutrophilic infiltration, proliferation, and periductal fibrosis/edema) favor cholangitis, whereas the presence and density of portal eosinophilia favor ACR. Portal inflammation is not a distinctive morphological finding.

Right lobe adult living-donor liver transplantation.

Living-donor liver transplantation is another treatment option to cadaveric liver transplantation in adult recipients. We report the outcomes of 49 right lobe adult living-donor liver transplantations performed at our institution between April 2003 and June 2006. The mean age of the recipients was 41.7 +/- 12.5 years. The median graft-to-recipient weight ratio was 1.2% +/- 0.4%. In recipients, the mean operative time was 10.6 +/- 2.7 hours. The mean number of blood transfusions administered was 4.1 +/- 5.1 units. The mean time spent in the intensive care unit was 2.3 +/- 1.5 days. In recipients, five vascular and five biliary complications occurred during the early postoperative period, and four vascular and two biliary complications developed in the late postoperative period. Thirteen of the 49 recipients died within 4 months of surgery. The mean age of the donors was 36.6 +/- 9 years. In the donors, the mean operative time was 6.4 +/- 1.6 hours, mean residual liver volume was 43.3% +/- 6.1%, and the mean hospital stay was 9.5 +/- 4.5 days. Two donors required an intraoperative blood transfusion. None of our donors died, but six complications occurred in four donors. The mean postoperative follow-up was 13.4 +/- 9.6 months. In conclusion, in Turkey, as in other countries, organ demand exceeds organ availability. Graft size presents a problem for adult recipients, but right lobe living donor transplant may be a life-saving option for these recipients when performed by experienced surgical teams.

Pediatric liver transplantation for acute liver failure.

The only proven therapy for patients unlikely to recover from acute liver failure (ALF) is liver transplantation. Correct diagnosis of these individuals and rapid referral to a transplant center are crucial. We evaluated 12 pediatric patients with ALF who underwent liver transplantation (LT) at our institution during a 3-year period. The reasons for transplantation were hepatitis A (3 patients); non-A, non-E hepatitis (3); autoimmune hepatitis (1); fulminant Wilson's disease (3); Amanita phalloides (mushroom) poisoning (1); and hepatitis B and toxic hepatitis with leflunomide treatment (1). Seven of the participants were female and five were male (mean age, 9.1 +/- 4.2 years). Three received right liver-lobe grafts, one received a whole liver graft, and the remainder received left or left-lateral liver lobe grafts. All patients recovered from hepatic coma the second postoperative day. Two patients died at postoperative days 57 and 71 due to adult respiratory distress syndrome and sepsis with multiorgan failure, respectively. One patient required retransplantation because of chronic rejection 7 months after the initial transplantation. That patient died 10 days after retransplantation because of sepsis. Nine patients were healthy at follow-up (range, 2-46 months). LT is the only treatment option for ALF in patients in countries with low organ-donation rates. In this scenario, donor preparation in a limited time frame is difficult. We have been able to decrease the duration of donor preparation to approximately 4 hours (including biopsy of the donated liver tissue).

Expanded criteria for hepatocellular carcinoma and liver transplantation.

In this study, we evaluated our early results of liver transplantation for hepatocellular carcinoma (HCC). Between January 2004 and June 2006, 26 patients (4 females, 22 males; aged 1.1-65 years) with preoperatively diagnosed or incidental HCC underwent liver transplantation at our center. Inclusion criteria (independent of tumor size and number of tumor nodules) were no invasion of major vascular structures and no evidence of extrahepatic disease. In 13 of the patients, tumors were beyond the Milan criteria. At this writing, at a mean follow-up of 16.5 months (range, 1-31 months), all patients were doing well with excellent graft function. The longest survival is 2.5 years, and our patient survival rate is 100%. There has been only 1 tumor recurrence, which occurred 4 months after liver transplantation. In conclusion, liver transplantation provides long patient and disease-free survival, even in patients with HCC that exceeds the Milan criteria.

Evaluation of posttransplantation malignancies compared with de novo tumors.

It is uncertain whether tumors arising in transplant patients resemble ones that develop de novo in pathogenesis, morphology, and behavior. This study sought to investigate some clinical, morphological, and immunohistochemical features of several posttransplantation malignancies compared with similar de novo tumors. The study group consisted of 40 malignant tumors encountered in 1350 transplant patients (1229 kidneys, 113 livers, 8 hearts) between 1986 and 2006. Tumors with 3 or more examples were compared with randomly selected controls. These included Kaposi's sarcoma (n=14); extranodal lymphoma (n=9); squamous cell carcinoma (n=6); and nodal lymphoma (n=3). The variables that were analyzed were the localization, predisposing lesions, degree of differentiation, and host response. For lymphomas, we also determined histological subtype, origin, and Ki-67 proliferation index. Most tumors (36/40, 90%) occurred in patients with renal transplants. However, the relative frequency was higher among liver transplant cases (3.53% vs 2.92% for kidney transplants). No malignancy was seen in heart transplant cases. Squamous cell carcinomas were better differentiated (P<.05) compared with controls and they were more frequently associated with precursor lesions (P<.05). Kaposi's sarcomas involved internal organs more frequently in posttransplant patients, and the Ki-67 proliferation index was higher in posttransplantation nodal lymphomas. However, these factors were not significantly different (P>.05). Our findings suggested that certain posttransplantation malignancies display unique characteristics compared with their de novo counterparts.

Role of heparin on TNF-alpha and IL-6 levels in liver regeneration after partial hepatic resection.

OBJECTIVES: The aim of this study was to investigate the effect of heparin on TNF-alpha and interleukin (IL)-6 levels and the complement system in liver regeneration in a murine model. MATERIALS AND METHODS: 32 Wistar albino female rats weighing between 180 and 250 g were included in the study. The rats were divided into four groups as follows: group 1, treated with partial (50%) hepatectomy and intravenous heparin 1,000 IU/kg in repeated daily doses; group 2, treated with sham operation and intravenous heparin 1,000 IU/kg in repeated daily doses; group 3, treated with partial (50%) hepatectomy, and group 4 (controls), treated with only sham operation. Before the surgical intervention and after a general anesthetic had been administered to all rats, blood was taken from the left ventricle of each rat, and each sample was assessed to determine total complement hemolytic activity (CH(50)/ml). On the 5th postoperative day, blood was taken to assess CH(50) activity and the levels of TNF-alpha and IL-6 via ELISA. Each rat was then killed by decapitation after which gravimetric analysis and immunohistochemical staining for proliferating cell nuclear antigen (PCNA) were performed. RESULTS: Serum CH(50) activity of group 1 was 4% as compared to 51% in group 3 (p = 0.01). The serum TNF-alpha level of group 1 was 43 pg/ml as compared to 86 pg/ml in group 3 (p = 0.002). The serum IL-6 level of group 1 was 19 pg/ml as compared to 44 pg/ml in group 3 (p = 0.02). The serum IL-6 level of group 2 was 4 pg/ml as compared to 44 pg/ml in group 3 (p = 0.005). According to the results of gravimetric analysis, the mean regeneration rate of group 1 was 4.4% as compared to 22% of group 3 (p = 0.001). The mean PCNA index values of group 2 was the highest of all groups (p = 0.01). However, the mean PCNA index value of group 1 was the lowest of all groups (p = 0.01). CONCLUSION: Because of its anti-inflammatory action via the complement system, heparin produced an unfavorable effect on liver regeneration.

Hepatic stellate cells in biopsies from liver allografts with acute rejection.

BACKGROUND: [corrected] Hepatic stellate cells (HSCs) are nonparenchymal elements that play a major role in fibrogenesis due to various pathologies. HSCs are easily activated by certain injuries, which produce contraction and relaxation of HSCs, resulting in hepatic microcirculatory disturbances. The present study sought to analyze the expression of alpha-smooth muscle actin (alpha-SMA) positive HSCs in liver allografts during acute rejection episodes (ARE), determining whether it was related to the pathogenesis of this immune response. MATERIALS AND METHODS: Using immunohistochemistry and a semiquantitative scoring system, the expression of alpha-SMA in HSCs was analyzed in liver allografts with ARE (group 1, n = 64) or without ARE (group 2, n = 20). Normal liver tissue from transplant donors (group 3, n = 53) served as the control materials. RESULTS: Significantly more alpha-SMA positive HSCs were found in group 2 than in the other two groups (P < .05). The minimal difference observed between groups 1 and 3 was not statistically significant. As well, no statistical association was found between expression of alpha-SMA and the clinical parameters of age, gender, etiology of liver failure, donor type (partial or whole), posttransplantation period, and liver function tests. CONCLUSIONS: While these results represent preliminary findings, it may be possible that HSC expression is a protective mechanism during ARE in hepatic allograft patients. If this is true, enhanced expression of this protein may mitigate ARE in liver allograft patients.

Frequency of recipient-derived chimerism and relationship with acute rejection and HLA tissue typing in transplanted livers.

BACKGROUND: We sought to determine the extent and time course of recipient-derived chimerism after transplantation and the relationship with acute rejection episodes (ARE) and HLA typing in hepatic allograft patients. PATIENTS AND METHODS: We studied 18 needle liver biopsy specimens from patients who had undergone orthotopic liver transplantation. Fluorescent in situ hybridization (FISH) analysis for X and Y chromosomes was performed in all cases with a sex mismatch. To evaluate the HLA matching, we used serological and polymerase chain reaction (PCR) methodology. RESULTS: There was a sex mismatch between the recipients and donors in all cases. X and Y chromosome chimerism was detected in 14 of 18 (83%; 31.14 +/- 27.4) patients. Also, no statistical association was found between the presence and the extent of chimerism and clinicopathological parameters (P < .05). CONCLUSIONS: Our results suggest that chimerism was frequently seen in liver allografts, but it did not influence the occurrence of ARE, tissue compatibility, or histopathological changes in the posttransplantation period. The clinical, immunological, and histopathological relevance of chimerism remain unclear. These results may relate to the small number of patients and disproportion of chimerism-positive versus-negative cases. Further prospective studies will be required to clarify these findings in a larger population of liver transplant patients.

Pedunculated solitary fibrous tumours arising from the pleura.

Solitary fibrous tumour (SFT) is one of the rare tumours which arise from visceral pleura. Klemperer and Rabin first described SFT as a distinct clinical entity among primary pleural tumoUrs in 1931. Approximately 820 cases have been reported in literature to date. The management of patients with SFT is complete resection of the tumour and follow up of the patient to detect any possible late recurrence. In the present paper, we report two cases of pedunculated solitary fibrous tumours of the pleura that appeared as a wandering chest nodule to which surgical resection undertaken at our hospital. The aim is to summarise our experience in the management of solitary fibrous tumour.

The risk of hypoparathyroidism after central compartment lymph node dissection in the surgical treatment of pT1, N0 thyroid papillary carcinoma.

OBJECTIVE: The role of central compartment lymph node dissection (CCLND) in the treatment of papillary thyroid carcinoma (PTC) is still controversial. The benefits of CCLND should be weighed against its potential risks. We aim to evaluate the positivity of central lymph nodes in pT1, N0 PTC and to establish the complication rates of total thyroidectomy (TT)+CCLND. PATIENTS AND METHODS: This is a retrospective study on prospectively collected data over a 45-month period. A total of 329 patients were included. Total thyroidectomy was performed in 130 (39.5%) of these patients due to benign thyroid pathologies, and 199 (60.5%) pT1, N0 PTC patients had TT+CCLND. Our TT technique was applied in the same way in both groups. Central lymph node positivity, the number of lymph nodes removed during CCLND and the operative complications were evaluated. T-test and chi-square analysis were conducted in independent groups for statistical evaluation. RESULTS: The rate of central lymph node positivity in TT+CCLND group was 38%. The average number of lymph nodes removed by CCLND is 10.2 (1-36). Complication rates between TT and TT+CCLND groups were statistically significant (3.8% vs. 11.1%, respectively) (p<0.05). The difference was found to be particularly more pronounced for transient hypocalcemia. Although there was no significant relation between the number of lymph nodes removed during CCLND and the number of parathyroid glands detected in the pathology specimens (p>0.05), the relation between the development of symptomatic hypocalcemia and the number of the parathyroid glands removed during surgery was significant (p <0.05). CONCLUSIONS: Central compartment lymph node metastasis in PTC is common. CCLND may increase the rate of transient hypocalcemia.

The impact of the multifocality and subtypes of papillary thyroid carcinoma on central compartment lymph node metastasis.

OBJECTIVE: Papillary thyroid carcinoma (PTC) may often appear as multifocal disease. Few studies demonstrated a higher rate of central compartment lymph node metastasis (CCLNM) in multifocal PTC patients. Therefore, the effect of different histological subtypes of multifocal PTC on CCLNM is another subject for further examination. The aim of the present study is to evaluate the rate of central lymph node positivity in multifocal PTC as compared to unifocal disease, and to identify the role of different histologic subtypes of PTC on central neck lymph node positivity. PATIENTS AND METHODS: Patients with PTC who underwent total thyroidectomy (TT) + central cervical lymph node dissection (CCLND) at authors' institution between January 2012 and June 2016 were included (n=274). Independent Samples t-test, Mann-Whitney U test and Chi-square tests were used to determine univariate associations, and multivariate analysis was conducted by logistic regression. RESULTS: The rate of CCLND positivity in multifocal PTC is higher than unifocal tumors and the difference is significant (p < 0.05). The univariate analysis demonstrated significant relation with male sex, lymphovascular invasion and size of dominant nodule > 10 mm regarding of CCLND positivity in multifocal PTC patients. The comparison between solitary and mixed histologic subtype of multifocal PTC is also significant (p < 0.05). CONCLUSIONS: Multifocality is an important risk factor for CCLNM. Male sex, dominant tumor size >10 mm and mixed histological subtype in multifocal PTC may play an important role in CCLND positivity.

Ki-67 proliferation index in Kaposi's sarcoma after renal transplantation: findings in skin-only cases versus cases with internal-organ involvement.

Kaposi's sarcoma (KS) is an angioproliferative condition that accounts for 6% of all malignancies in organ transplant patients. When we review the literature, the results of the studies comparing the different stages and the proliferative activity of the tumor are challenging. However, we found no previous study on Ki-67 protein expression in KS that correlates skin and organ lesions. In the current study, we investigated whether there is a correlation on the proliferative activity between skin and internal organ lesions in KS. Proliferative activity of 13 biopsy specimens of KS was assessed immunohistochemically using the monoclonal antibody MIB-1 (Ki-67). Mann-Whitney U test is used for statistical analysis and a P value < .05 was considered significant. Seven of 13 cases were skin and six were internal organ KS. For skin lesions, the mean MIB-1 proliferation index was 14.5%, and it was 13% for organ lesions. There was no significant association between skin and internal organ KS in regard to MIB-1 PI (P > .05). The findings suggested that the proliferative activity in KS does not differ in skin and organ lesions. On the other hand, it should be considered that the number of cases in our study was limited and further studies with a larger series are needed.

Angiotensin-converting enzyme and endothelial constitutive nitric oxide synthase polymorphisms in Turkish renal transplant population and possible influence on renal artery atherosclerosis and graft survival.

BACKGROUND: Renal transplant recipients are prone to accelerated atherosclerosis secondary to immunosuppressants, which may decrease graft survival. We sought to analyze the effects on renal graft survival of atherosclerotic degeneration in the renal artery and the influence of angiotensin-converting enzyme (ACE) endothelial constitutive nitric oxide synthase (ecNOS) gene polymorphisms. METHODS AND PATIENTS: Thirty three renal transplant recipients (25 men) of mean age 28.4 +/- 9.6 years, received organs from 11 living related donors and were followed for at least 36 months. Genotyping was performed for the insertion/deletion ACE (I/D), angiotensin (AGT) (M-->T, 235), angiotensine 1 receptor (A-->C, 1166), angiotensin 2-receptor (A-->G, 1223), and ecNOS (b-->a, intron4) gene polymorphisms. Renal artery biopsies were performed during transplantation surgery to analyze the presence of atherosclerosis. RESULTS: Pathological examination indicated that 18 donor specimens and nine recipient specimens had atherosclerotic degeneration. Survival analysis (36 months) indicated that graft survival rates of recipients who had atherosclerosis in the renal artery and who received an organ from donors with an atherosclerotic renal artery were shorter than in their counterparts (P = .02, P = .04, respectively). Comparison of genetic variations of recipients revealed that CC/TC variation of AGT was higher in patients with atherosclerosis (81% vs 53%, P = .03). There was no significant difference between groups in means of other gene polymorphisms. CONCLUSION: Renin-angiotensin system gene polymorphism analysis of patients in renal transplantation waiting list may provide information about allograft survival and posttransplant atherosclerotic degeneration at graft vasculature of young transplant recipients.

Pelvic retroperitoneal paraganglioma mimicking an ovarian mass.

A 75-year-old hypertensive woman was referred with ultrasound findings of a 40 x 35 mm semi-solid right adnexal mass and right hydroureteronephrosis. She complained of headache and right-sided back pain. Computed tomography demonstrated a cystic adnexal mass that did not appear to originate from the right ovary and grade 2 hydroureteronephrosis. Magnetic resonance imaging indicated that the mass originated from the right ovary. Tumor markers were in the normal range. Exploratory laparotomy was performed to determine the origin of the lesion, and revealed a retroperitoneal mass obstructing the right ureter. The mass was completely removed and and the histopathologic diagnosis was paraganglioma.

The analysis of gastrointestinal amyloidosis in 78 patients with chronic renal failure.

Systemic amyloidosis is not a single disease, but the product of a variety of diseases. Amyloid proteins are insoluble fibrils that are deposited extracellularly in many organ tissues. They stain with Congo red and appear apple green under polarized light. Definitive diagnosis and classification ofamyloidosis requires histologic examination of tissue samples. Gastrointestinal tract involvement is common, and all parts of the system can be affected Immunohistochemical studies have shown that amyloid deposited in the gastrointestinal system is most often of the AA, A kappa, or A lambda types. Another type of amyloidprotein, beta-2 microglobulin (beta2M), predominantly affects the musculoskeletal system, and is usually seen in patients who have been on long-term hemodialysis. Mixed systemic amyloidosis (beta2M and AA) is seen only rarely in these patients. In this study, we attempted to answer why this is so, and examined whether or not mixed amyloidosis is related to amyloidogenesis. We studied gastrointestinal tissues from 78 chronic renal failure patients who had systemic amyloidosis with gastrointestinal involvement. A total of 115 endoscopic samples and 1 jejunal resection specimen were analysed immunohistochemically. Immunohistochemical testing using a panel of antisera directed against two major amyloid fibril proteins (AA-Monoclonal, Dako-, and beta2M-Polyclonal, Dako-) showed that all samples contained AA amyloid, but not beta2M type protein. These findings can be explained by the patients' relatively short average duration of hemodialysis and the predominance of endoscopic biopsy samples in our study.