Acute fulminant hepatic failure in a woman treated with phenytoin and trimethoprim-sulfamethoxazole.

Massive hepatic necrosis following exposure to phenytoin and trimethoprim-sulfamethoxazole is a rare occurrence and to the best of our knowledge has not been reported previously. Acute hepatic failure following administration of trimethoprim-sulfamethoxazole has rarely been seen, and only 4 cases have been well documented pathologically. We report a case of acute liver failure in a 60-year-old woman following ingestion of phenytoin and trimethoprim-sulfamethoxazole concomitantly over a 9-day period. Autopsy findings revealed acute fulminant hepatic failure. This case demonstrates the effects of chemical-chemical interactions in the potentiation of hepatotoxicity of single agents and specifically illustrates the need for discontinuing trimethoprim-sulfamethoxazole in the presence of early liver injury.

A study of adult T-cell leukemia/lymphoma incidence in central Brooklyn.

Adult T-cell leukemia/lymphoma (ATL), a rare outcome of infection with human T-lymphotropic virus (HTLV-I), is endemic in central Brooklyn, which has a large Caribbean migrant population. Previous studies have suggested that HTLV-I prevalence in central Brooklyn may be similar to that recorded in the Caribbean islands. We established a pilot 1-year surveillance program to identify cases of ATL in 7 of 10 hospitals serving the residents of 18 zip codes of central Brooklyn with a combined population of 1,184,670. Of the 6,198 in-patient beds in the catchment area, approximately 83% were covered. Twelve incident cases of ATL were ascertained, all among persons of Afro-Caribbean descent, indicating an annual incidence in African-Americans in this community of approximately 3.2/100,000 person-years. Unexplained hypercalcemia was the most useful screening method, identifying 3 of 5 patients not referred for possible ATL by a local hematologist. The female:male ratio was 3:1. The age pattern was different from that reported in the Caribbean Basin and closer to the pattern seen in Japan. Our study supports evidence that HTLV-I infection and ATL are endemic in central Brooklyn and suggests that a more intensive surveillance program for this disease coupled with intervention efforts to reduce HTLV-I transmission are warranted.

Clinical, laboratory, radiographic, and histopathologic features of methotrexate-associated lung injury in patients with rheumatoid arthritis: a multicenter study with literature review.

OBJECTIVE: To describe the clinical, laboratory, radiologic, and histopathologic features of methotrexate (MTX)-induced lung injury in a combined cohort of selected patients with rheumatoid arthritis (RA) and all cases reported in the English-language literature. METHODS: Retrospective combined cohort review and abstraction from the medical literature. Case reports were obtained from 6 centers that had 4 or more cases of potential MTX lung injury per site. RA patients who were seen between 1981 and 1993 and who satisfied predetermined criteria for the presence of MTX lung injury were identified. RESULTS: Twenty-seven patients satisfied the criteria for definite MTX lung injury, and 2 for probable MTX lung injury. Predominant clinical features of MTX lung injury included shortness of breath in 27 patients (93.1%), which was present for 23.5 +/- 22.3 days (mean +/- SD), cough in 24 (82.8%), present for 26.9 +/- 28.5 days, and fever in 20 (69.0%), present for 10.4 +/- 12.8 days. Five patients (17.2%) died, compared with 12 of 68 (17.6%) reported in the medical literature. Four of the 6 patients who were re-treated with MTX after an initial pulmonary event developed recurrent lung toxicity, resulting in 2 deaths, compared with a recurrence rate of 3 of 6 in the literature. CONCLUSION: MTX lung injury is most often a subacute process, in which symptoms are commonly present for several weeks before diagnosis. Approximately 50% of the cases are diagnosed within 32 weeks from initiation of MTX treatment. A patient who recovers from MTX lung injury should not be re-treated. Earlier recognition and drug withdrawal may avoid the serious and sometimes fatal outcome that has been observed in this and other studies.

Risk factors for methotrexate-induced lung injury in patients with rheumatoid arthritis. A multicenter, case-control study. Methotrexate-Lung Study Group.

BACKGROUND: Toxicity limits the use of methotrexate. OBJECTIVE: To identify risk factors for methotrexate-induced lung injury in patients with rheumatoid arthritis. DESIGN: Case-control study. SETTING: One private and five academic rheumatology practices. PARTICIPANTS: Methotrexate recipients with rheumatoid arthritis with and without lung injury. MEASUREMENTS: Potential risk factors examined were sociodemographic and lifestyle characteristics, medical history, clinical and ancillary features and treatment of rheumatoid arthritis before methotrexate therapy, and characteristics of methotrexate therapy. Cases of lung injury were defined according to the modified criteria of Searles and McKendry. RESULTS: Ninety-four percent of the study participants were white, and 67% were women. Case-patients (n = 29) were older than controls (n = 82) (61.5 compared with 54.5 years of age). The strongest predictors of lung injury, after adjustment for other variables, were older age (odds ratio [OR], 5.1 [95% CI, 1.2 to 21.1]), diabetes (OR, 35.6 [CI, 1.3 to infinity]), rheumatoid pleuropulmonary involvement (OR, 7.1 [CI, 1.1 to 45.4]), previous use of disease-modifying antirheumatic drugs (OR, 5.6 [CI, 1.2 to 27.0]), and hypoalbuminemia (OR, 19.5 [CI, 3.5 to 109.7]). Previous use of disease-modifying antirheumatic drugs and hypoalbuminemia had very large attributable risks. CONCLUSION: Knowledge of the risk factors that predispose patients with rheumatoid arthritis to the toxic effects of methotrexate on the lung may provide a rationale for monitoring high-risk patients and may facilitate their management.

Estrogen receptor immunocytochemistry in endometrial carcinoma: a prognostic marker for survival.

UNLABELLED: Only a few parameters such as tumor grade and stage are of value in prognosticating disease course in endometrial carcinoma. Biochemical steroid hormone receptor assays could also be useful but are difficult to perform and interpret. Immunocytochemical assay (ICA) might be the method of choice for detecting endometrial receptors. METHODS: Frozen tissue from 78 cases of endometrial adenocarcinoma was examined for the presence of estrogen (ER) and progesterone receptors (PgR) with specific monoclonal anti-receptor antibodies and the peroxidase-antiperoxidase method. In over 60 cases, frozen tissue was also assayed for ER and PgR by biochemical means. RESULTS: Fifty-five (71%) of the endometrial carcinomas were ERICA-positive and 55 (71%) PgRICA-positive. Although both ERICA and PgRICA correlated significantly with biochemical ER and PgR only ERICA was predictive of survival. A woman with a negative ERICA was 4 times more likely to die of her disease than if she were ERICA-positive (P = 0.009; mean follow-up, 37.5 months). Three cases ERICA-positive and PgRICA-negative survived while 3 others ERICA-negative and PgRICA-positive died. CONCLUSION: ERICA, a technique easy to perform and interpret at the community hospital level, appears to provide prognostic information independent of tumor stage and grade. Such information might be of value in planning postoperative therapies for women with endometrial cancer.

Light and electron microscopic analysis of sequential liver biopsy samples from rheumatoid arthritis patients receiving long-term methotrexate therapy. Followup over long treatment intervals and correlation with clinical and laboratory variables.

OBJECTIVE: To describe liver histopathologic features and ultrastructural changes in a prospectively studied cohort of rheumatoid arthritis (RA) patients receiving long-term methotrexate (MTX) therapy, and to seek correlations between these changes and simultaneously measured laboratory indices of liver function. METHODS: This was a long-term, prospective, open observational study. Twenty-seven outpatients with RA who began therapy with MTX and continued treatment for extended periods underwent baseline and followup liver biopsies. One hundred seventy liver biopsy specimens were analyzed by light microscopy (LM) and assessed according to a modified Roenigk score and a newly devised numerical grading system. Ninety-three biopsy specimens were also analyzed by electron microscopy (EM). Blood samples were obtained at 4-6-week intervals for determination of bilirubin, alkaline phosphatase, aspartate aminotransferase (AST), and albumin levels, and the weekly dosage of MTX was adjusted if there were abnormalities in the AST or albumin level. A mean of 6.3 liver biopsies per patient were obtained over a mean followup period of 8.2 years (range 2-13 years). RESULTS: The modified Roenigk score was significantly different from baseline at year 3, when it increased from a mean of 1.8 to 2.3 (P = 0.05) and at year 6, when it increased to 2.4 (P = 0.04), but this was not considered clinically meaningful. No other significant changes from baseline were observed by either LM grading system. No significant progression was observed by EM over the course of the investigation. Increases in serial measurements of AST correlated with both the modified Roenigk score (r = 0.21, P = 0.016) and the numerical rating score (r = 0.19, P = 0.027). CONCLUSION: Patients with RA who are receiving weekly single-dose oral MTX therapy exhibit little deterioration in hepatic architecture by LM or EM when the dosage of the drug is adjusted for abnormalities in AST and serum albumin, monitored at frequent intervals.

Immunostaining for prostate cancer androgen receptor in paraffin identifies a subset of men with a poor prognosis.

BACKGROUND: Knowledge of androgen receptor (AR) content could help predict hormone response and disease course in prostate cancer. However, determination of AR by biochemical assay is difficult. An immunohistochemical assay (ICA) would solve most difficulties and be especially useful if it could be performed on paraffinized tissue. EXPERIMENTAL DESIGN: AR was studied in paraffin sections from 90 men for whom endocrine response, survival (except one case), and/or biochemical AR was known. After Ag retrieval in a microwave oven, a polyclonal anti-AR Ab was used with the peroxidase antiperoxidase method. Results were semiquantified using a Histoscore (Hscore) and were correlated with biochemistry, endocrine response, and survival. RESULTS: Only 15 patients were AR-negative. AR-ICA did not correlate with biochemistry, Gleason score, stage, or ethnicity but did correlate with endocrine response and survival. The average Histoscore was significantly lower in patients with progressive disease (p < 0.05). In a Cox's regression analysis of survival (mean follow-up = 30 months) AR-ICA was a significant predictor (p = 0.015). Risk of death was 2.5 times greater for a patient with a negative assay compared with one with a positive result. CONCLUSIONS: Our data indicate that AR status by ICA may be a useful predictor of survival and endocrine response in prostate cancer. Further studies are needed to confirm these results because the assay could impact significantly on management.

P-glycoprotein is expressed in parathyroid epithelium and is regulated by calcium.

P-glycoprotein (Pgp), the multidrug resistance (mdr) gene product, has been described in normal tissues with diverse physiologic functions. A broad role as a transporter protein for toxins, hormones, and physiologic metabolites has been provisionally deduced, based on structural analysis and immunoanatomic localization. Recently, significant levels of Pgp have been demonstrated in endocrine and hormonally responsive tissues and tumors. We examined calcium-regulated, clonal parathyroid epithelial (PT-r) and endothelial cells (BPE-1) and frozen parathyroid tissue from normal human parathyroid, parathyroid hyperplasia, parathyroid adenoma, and parathyroid carcinoma for expression of the multidrug resistance gene (Mdr1) and Pgp utilizing Northern and Western analysis and immunohistochemistry. We also investigated the effect of extracellular calcium (eCa) on Pgp expression in PT-r cells at the molecular/cellular level. Immunohistochemistry, utilizing three murine monoclonal antibodies (MAbs)--C494, JSB-1, and C219--which recognize spatially distinct cytoplasmic epitopes of Pgp, revealed strong immunoreactivity in PT-r cells, normal parathyroid, and parathyroid hyperplasia, and weak immunostaining in parathyroid adenomas. BPE-1 cells, endothelial cells, and parathyroid carcinoma were negative. PT-r cells showed a single 130 kDa band (120 KDa after glycosidase treatment) on Western blot and a 4.6 kb transcript on Northern analysis, consistent with Pgp. Western and Northern blot analysis of PTr cells cultured in different eCa concentrations showed that eCa up-regulated Pgp expression.

Immunohistochemical detection of P-glycoprotein in Ewing's sarcoma and peripheral primitive neuroectodermal tumors before and after chemotherapy.

The authors evaluated P-glycoprotein expression in a total of 35 cases of Ewing's sarcoma and peripheral primitive neuroectodermal tumors (PNET). Fifteen cases had matched tumors before and after treatment. The 20 unmatched tumors included 14 pretreatment PNETs and Ewing's sarcomas and 6 posttreatment Ewing's sarcomas. Two antibodies, C219 and JSB-1, were used. Immunoreactivity was almost exclusively membranous. Variability in the number of positive cells and in staining intensity was noted within individual tumors. Among the 15 matched tumors, 7 were positive for P-glycoprotein before treatment; 6 of these remained positive after treatment. Four of the 8 that were negative for P-glycoprotein before treatment became positive after treatment. Of the unmatched tumors, 9 of 14 pretreatment and 3 of 6 posttreatment tumors were positive. When relapse-free survival time, based on the presence or absence of P-glycoprotein positivity in pretreatment tumor samples, was evaluated in this group, no significant difference was found (P2 = .92); however, the numbers are too small to draw definitive conclusions. The high incidence of positive primary tumors suggests that P-glycoprotein expression is probably intrinsic in Ewing's sarcoma and PNET and not necessarily induced by therapy.

Estrogen receptor immunocytochemistry: the promise and the perils.

Estrogen receptor immunocytochemistry (ERICA) is favored over dextran-coated charcoal (DCC) or sucrose gradient assay (SGA) by many pathologists and oncologists since it allows an estimation of tumor cell and tissue heterogeneity and permits assays to be performed on specimens not suitable for DCC/SGA. Additionally, ERICA can be performed with greater ease and with less expense at the level of the community hospital pathology laboratory. Initially, like DCC/SGA, ERICA had to be done on fresh or frozen tumor samples or face a significant loss in sensitivity when applied to formalin-fixed, paraffin-embedded sections. Recently, several anti-estrogen receptor (ER) antibodies have appeared which can be successfully employed to assay routinely prepared tissue sections if used in conjunction with new antigen-retrieval techniques such as the microwave oven and citrate buffers. However, more work is needed to correlate results of these new procedures with biochemical ER assays, endocrine response, and survival before they can be reliably employed as prognostic parameters. Furthermore, if any ER assay is to be useful and valid, strict attention must be paid to details of specimen collection, freezing, and fixation in order to inhibit receptor degradation and false negative results.

Prolonged alpha interferon therapy for chronic delta hepatitis: effect on liver histopathology.

Alpha interferon therapy in patients with chronic delta hepatitis treatment was associated with a decrease in serum aminotransferase activities and disappearance or decrease in serum levels of HDV RNA. Serum biochemical and serological changes were associated with amelioration of hepatic injury and a decrease (but not a disappearance) in hepatic HDAg on liver biopsy. Two cases lost HBsAg during therapy, only one of whom had lost hepatic HDAg entirely at the end of therapy. Interestingly, a decrease in HDV replication was associated with an apparent increase in HBV replication in some cases.

Mutations of p53 gene in hepatocellular carcinoma: roles of hepatitis B virus and aflatoxin contamination in the diet.

BACKGROUND: Mutations of the p53 tumor suppressor gene have been reported in 50% of patients with hepatocellular carcinoma (HCC) from China and South Africa. These reports suggested an association of p53 mutations with high levels of aflatoxin in the diet. Most studies of p53 and HCC, however, have not fully evaluated the possible role of the hepatitis B virus (HBV). Aflatoxin is a substance produced by food mold that is known to cause HCC in experimental animals. PURPOSE: The purpose of this study was to evaluate the relationship of p53 gene mutation to high or low levels of aflatoxin in the diet and to HBV infection. METHODS: p53 protein and hepatitis B surface antigen (HBsAg) were evaluated by immunohistochemistry using the avidin-biotin-peroxidase system in paraffin-embedded specimens of HCC and of adjacent nontumorous liver tissue from 43 patients. Tissue specimens from three normal human livers were also evaluated. HCCs and adjacent nontumorous liver tissues were obtained from 23 patients from Qidong, China, where aflatoxin levels in the diet are high, and from 20 patients from two regions in the United States (patients from the National Institutes of Health, Bethesda, Md., and Kuakini Medical Center, Honolulu, Hawaii), where aflatoxin levels in the diet are low. RESULTS: Mutant p53 protein was detected in the nuclei of HCCs from 14 (61%) of 23 patients from China and from three (30%) of 10 patients and six (60%) of 10 patients, respectively, from the two regions of the United States. A statistically significant association between detection of mutant p53 protein in HCC cells and the detection of HBsAg in hepatocytes of the adjacent nontumorous liver tissue was observed in patients from China and the United States considered together. CONCLUSION: Mutations of the tumor suppressor gene p53 in hepatocellular carcinomas are not limited to patients from geographic regions where the ingestion of aflatoxin is high. In many patients, these mutations may be associated with HBV infection. IMPLICATIONS: The possible interaction of chronic HBV infection and p53 gene mutation, suggested by these data, indicates a mechanism by which HBV infection beginning early in life could contribute to the subsequent development of HCC.

Detection of P-glycoprotein on endothelial and endocrine cells of the human pancreatic islets by C 494 monoclonal antibody.

P-glycoprotein, an integral membrane protein acting as an energy-dependent efflux pump, has been detected immunocytochemically in the human pancreatic islets using C 494 monoclonal antibody. Intense P-glycoprotein immunoreactivity was found in both endothelial cells of islet blood capillaries and in endocrine cells. Strong expression of P-glycoprotein has been found in the capillary blood vessels at blood-tissue barrier sites and in numerous kinds of cells with secretory/excretory function. Therefore the present findings suggest that P-glycoprotein may play a role in controlling the composition of the extracellular fluids and the intracellular milieu of endocrine islet cells and possibly in regulating their secretory activity.

A pilot study of ribavirin therapy for chronic hepatitis C.

Interferon-alpha therapy is of proven efficacy in chronic hepatitis C, but it is not universally effective and may be associated with intolerable side effects. Ribavirin is a nucleoside analog with a broad spectrum of antiviral action. We conducted an uncontrolled pilot study of ribavirin therapy in 13 patients with chronic hepatitis C. Ribavirin was given for 6 mo, in a dose that was increased, at 2-mo intervals, from 600 mg to 1,000 mg to 1,200 mg/day. Serum ALT levels gradually decreased in all 13 treated patients; the mean percentage of decrease was 67% (from 210 U/L [range = 109 to 593] to 63 U/L [range = 22 to 108 U/L]; p = 0.0006) after 6 mo of treatment. Serum aminotransferase levels fell to the normal range in four patients (31%). In the 3 to 6 mo after cessation of ribavirin therapy, serum aminotransferase activities gradually rose to near pretreatment levels in all but one patient. Therapy was associated with a significant decrease in the geometric mean titer of hepatitis C virus RNA in serum (1:1,981 vs. 1:199; p less than 0.02) although no patients lost hepatitis C virus RNA from serum during therapy. No significant improvement was seen in liver histological appearance. Ribavirin therapy resulted in mild, reversible hemolysis; no patient exhibited symptomatic anemia. These findings suggest that ribavirin has a beneficial effect in patients with chronic hepatitis C, although further studies are needed to determine how ribavirin is best used.

Transforming growth factor-alpha in human hepatocellular carcinoma and coexpression with hepatitis B surface antigen in adjacent liver.

BACKGROUND: Hepatitis B virus (HBV) infection is closely associated with the development of hepatocellular carcinoma (HCC) in many patients, but the mechanisms by which HBV contributes to HCC are not known. Transforming growth factor-alpha (TGF-alpha), a regulator of growth and regeneration in rat liver that can be found in high levels in some human cancers, theoretically could play such an intermediate role in the development of HCC. METHODS: The expression of TGF-alpha and its relation to the HBV antigens were evaluated in human HCC and adjacent nontumorous livers from 33 patients from the United States and China using immunoperoxidase staining of paraffin-embedded sections. RESULTS: TGF-alpha was detected in HCC from 27 of 33 (82%) patients; the frequencies were similar in patients from the United States and China. TGF-alpha was detected in HCC more frequently in patients whose adjacent nontumorous livers had detectable hepatitis B surface antigen (HBsAg) and/or hepatitis B core antigen (HBcAg) than in those whose adjacent livers lacked HBsAg and HBcAg. Detection of TGF-alpha was not affected by tumor size, histologic type, or grade. TGF-alpha was detected in adjacent nontumorous livers from 31 of 33 patients (94%). Coexpression at a high intensity of TGF-alpha and HBsAg in the same hepatocytes could be demonstrated by specific staining of consecutively cut sections for 17 of 33 patients (52%). CONCLUSIONS: TGF-alpha is expressed at a high level in 82% of human HCC. Localization of HBsAg within the same hepatocytes as TGF-alpha suggests a possible interaction between HBV and TGF-alpha during hepatocarcinogenesis in humans. Stimulation of TGF-alpha expression could be part of a chain of events by which HBV contributes to the development of HCC in some patients.

Patterns of basement membrane laminin distribution in nonneoplastic and neoplastic thyroid tissue.

Laminin, a major basement membrane component, is typically absent or partially lost around the epithelial elements of most invasive carcinomas. To evaluate the distribution of laminin in both primary and metastatic thyroid tumors, we studied 14 benign thyroid lesions (eight adenomas, two Graves' disease, two Hashimoto's thyroiditis, one adenomatous hyperplasia, one nodular goiter), 20 carcinomas (seven papillary, six tall cell variant, four follicular, three Hürthle), and eight metastases (five tall cell variant, three follicular) utilizing a polyclonal antibody against highly purified, nidogen-free laminin. All benign lesions showed positive, linear immunostaining along basement membranes. Partial loss or absence of laminin was seen in the solid areas of all types of thyroid carcinomas examined; well-differentiated papillary and follicular tumors, as well as papillary and follicular areas of more poorly differentiated neoplasms, maintained linear laminin immunostaining in the papillary cores beneath the epithelial cells and around follicles. A similar correlation between laminin deposition and architectural organization was seen in metastatic lesions. Hürthle cell carcinomas had a unique fragmented, pericellular immunostaining pattern around individual tumor cells, suggesting uncontrolled laminin synthesis. Our findings suggest that preservation of laminin production in thyroid tumors reflects their degree of differentiation and that absence of laminin correlates with lack of structural organization rather than reflecting invasive and metastatic potential.

Measurements of iron status in patients with chronic hepatitis.

Eighty patients with chronic viral hepatitis were screened for evidence of iron overload. Elevated serum iron values were noted in 36% of cases; serum ferritin values were above normal in 30% of men and 8% of women. Twenty-eight additional patients with chronic hepatitis for whom liver tissue was available for determination of iron content were evaluated to study the significance of iron overload in association with chronic hepatitis. Although 46% had elevated serum iron, ferritin, or transferrin-saturation levels, the hepatic iron concentration was elevated in only four cases, and the hepatic iron index was in the range for hereditary hemochromatosis (greater than 2.0) in only two of these. Serum aspartate aminotransferase activities correlated with serum ferritin levels in these patients, suggesting that ferritin and iron levels were increased in serum because of their release from hepatocellular stores associated with necrosis. Thus, in patients with chronic hepatitis in whom hereditary hemochromatosis is suspected, a liver biopsy should be performed with quantitation of hepatic iron and calculation of the hepatic iron index to confirm the diagnosis.

Location, incidence, and malignant potential of duodenal gastrinomas.

Duodenal gastrinomas are increasingly found at surgery, yet information about their location and characteristics is based on the results of either pooled series or retrospective reviews of small numbers of selected cases. To address these issues we have analyzed the location, incidence, and malignant potential of duodenal gastrinomas in 65 consecutive patients who underwent removal of all tumor as part of a 10-year prospective study to resect gastrinomas in patients with sporadic Zollinger-Ellison syndrome. The primary gastrinoma was located in the duodenum in 24 patients (37%). There were 19 men and five women aged 32 to 69 years (mean 49.4 years), with symptoms for 0.6 to 35 years (mean 7.9 years). Preoperative studies included serum gastrin levels of 114 to 35,798 pg/ml (mean 2060 pg/ml), basal acid output of 7 to 95 mEq/hr (mean 37.6 mEq/hr), and a positive secretin test result in 22 patients. Preoperative imaging studies identified tumor in the duodenal area in 11 patients (46%), but most positive imaging findings were metastatic gastrinoma in lymph nodes, and the primary duodenal tumor itself was identified in only two patients. Portal venous sampling had a localizing gastrin gradient in the inferior or superior pancreaticoduodenal vein in 17 of 23 patients (74%). Each of the 24 patients had a single, small duodenal wall tumor of 2.8 to 10.1 mm diameter (mean 6 mm). Each tumor stained positive for gastrin by immunohistochemistry. Seventeen tumors (71%) were located in the first portion of the duodenum, five (21%) in the second, and two (8%) in the third. Each tumor originated in the submucosa, and 13 (54%) were limited to the submucosa, whereas 11 (46%) were locally invasive, four (16%) extending into the muscularis mucosa and seven (29%) into the muscularis propria. Thirteen patients (54%) had spread to regional lymph nodes, whereas two (8%) had liver metastases. Lymph node metastases were seen with larger duodenal tumors (mean 7.1 vs 5.4 mm; p less than 0.01). The data suggest that a single duodenal wall gastrinoma is a common cause of Zollinger-Ellison syndrome (37%). These small (less than 1 cm) tumors are located in the submucosal layer of the proximal duodenum (92%) and are malignant more often than previously thought (54%).