Improved safety of glucagon testing for pheochromocytoma by prior alpha-receptor blockade. A controlled trial in a patient with a mixed ganglioneuroma/pheochromocytoma.

The glucagon stimulation test has been superseded in recent years by the clonidine suppression test because it can provoke dangerous increases in blood pressure in patients with pheochromocytomas. We describe the first patient in whom a pheochromocytoma was diagnosed by a glucagon test, after which the blood pressure (but not the plasma catecholamine) response to a second injection of glucagon was blocked by pretreatment with phenoxybenzamine. After the tumor (which contained both pheochromocytoma and ganglioneuroma tissue) was removed, a third glucagon test result was negative. This experience suggests that patients with normal plasma catecholamine levels who are suspected of harboring a pheochromocytoma may be accurately diagnosed, but potentially dangerous increases in blood pressure may be minimized, by performing the glucagon test after alpha-adrenergic blockade.

Effective genetic therapy of established medullary thyroid carcinomas with murine interleukin-2: dissemination and cytotoxicity studies in a rat tumor model.

Replication-defective adenovirus (AdCMVmIL2) expressing murine interleukin-2 was directly injected into rat medullary thyroid carcinomas to examine antitumor activity. AdCMVmIL2 cured 42.9% of all treated tumor bearing animals. Most cured rats were protected against tumor growth after subsequent rechallenge with wild-type tumor cells, reflecting the immunity obtained from the original treatment. Studies of viral dissemination showed that the intratumoral inoculated viruses can enter the circulation, infect peripheral tissues, and express genes driven by the CMV promoter. Liver is the main target organ. In a toxicity study, AdCMVmIL2 was administered i.v. at a dose five times higher than that given directly into tumor. No detectable side effect was found. Histological studies showed variable degrees of lymphocyte infiltration in the livers of studied animals, and no functional change indicated by the normal serum level of glutamic oxalacetic transaminase and glutamic pyruvic transaminase was found in all animals studied. These data demonstrate that AdCMVmIL2 is an effective antitumor agent in this animal model, and that virus treatment can be given without significant toxicity to other organs.

Suppression of development of experimental autoimmune thyroiditis by oral administration of thyroglobulin.

Experimental autoimmune thyroiditis (EAT), which to some extent represents an experimental model of human chronic lymphocytic thyroiditis, is an organ-specific autoimmune disease characterized by autoantibody production to thyroid antigens (Ag) and mononuclear infiltration of the thyroid gland. EAT induced by immunization with human thyroglobulin (hTG) with Freund's adjuvant in CBA/J (H-2K) mice is associated with prominent B and T cell responses. We report that oral administration of hTG effectively reduces the immune responses in EAT in mice in an Ag-specific manner. Both cellular and humoral immune responses are reduced in a dose-dependent manner. Histological evidence of disease is dramatically reduced. Suppression of the immune responses is seen 2 weeks after Ag challenge, with partial inhibition of proliferative and antibody responses. Six weeks after immunization, further inhibition is observed of both T and B cell responses. Hyporesponsiveness of T and B cell reactivity is seen only to hTG; T and B cell responses to other immunogens are not affected, including purified protein derivative and the nonrelated Ag BSA. This model may provide the basis for immunotherapy of autoimmune thyroid diseases in man.

Immunosuppression of thyroiditis.

Immunization of mice with 50 micrograms human thyroglobulin (TG) in complete Freund's adjuvant leads to histological thyroiditis; production of IgG, IgA, and IgM anti-TG antibodies; and in vitro proliferative responses after incubation of lymphocytes with TG. Oral administration of 500 micrograms TG at four intervals before Tg immunization and once afterward causes up to 80% suppression of these responses. The effect is antigen specific and dose dependent. Feeding TG after immunization produces a 40% reduction in responses. We wished to define the mechanism of this antigen-specific oral tolerization. Popliteal lymph nodes (PLN) of orally tolerized animals (T) are reduced in size compared to those in immunized (I) animals not fed TG. PLN and mesenteric lymph nodes (MLN) of I animals produce interleukin-2 (IL-2) and interferon-gamma (IFN gamma) after in vitro incubation with TG, typical of an inflammatory immune response. PLN and MLN of tolerized animals do not proliferate in response to antigen, do not produce IL-2 or IFN gamma, but do not produce the cytokines IL-4 and transforming growth factor-beta (TGF beta). Mixing in vitro of spleen cells from T and I animals causes a reduction in the immune response when incubated with TG, but no reduction in response to purified protein derivative (PPD) (the antigen in complete Freund's adjuvant). When T splenocytes are incubated with TG and PPD together, the response to TG and PPD is suppressed. Partially purified CD8+ cells from tolerized animals produce IL-4 and TGF beta after exposure to human TG and induce suppression, whereas partially purified CD4+ cells produce IL-2 and IFN gamma and do not cause suppression. MLN cells do not proliferate in response to antigen, but do produce inhibitory cytokines. T animals appear to shift the immune response from a Th-1 helper cell subset response to a Th-2 helper cell immunosuppressive response. In this model, oral tolerization produces a dramatic reduction in the immune response. Exposure of MLN to oral TG appears to cause the production of regulatory cells that migrate to spleen and PLN. In vitro studies demonstrate that on exposure to antigen, these regulatory cells produce IL-4 and TGF beta, which suppress all aspects of specific immune responsiveness and nonspecifically suppress other ongoing immune responses (bystander effect). Oral tolerization may include some element of T cell deletion or anergy. This model defines an experimental system with possible relevance to immunosuppression of human autoimmune thyroid disease.

Natural history, treatment, and course of papillary thyroid carcinoma.

We have analyzed the course of papillary thyroid carcinoma in 269 patients managed at the University of Chicago, with an average follow-up period of 12 yr from the time of diagnosis. Patients were categorized by clinical class; I, with intrathyroidal disease; II, with cervical nodal metastases; III, with extrathyroidal invasion; and IV, with distant metastases. Half of the patients had a history of thyroid enlargement known, on the average, for over 3 yr. In 15% of patients given thyroid hormone, the mass decreased in size. The peak incidence of cancer was when subjects were between 20-40 yr of age. Tumors averaged 2.4 cm in size; 21.6% had tumor capsule invasion, and 46% of patients had multifocal tumors. Sixty-six percent of the patients had near-total or total thyroidectomy. The overall incidence of postoperative hypoparathyroidism was 8.4%, but the incidence was zero in 83 near-total or total thyroidectomies carried out by 1 surgeon. Twenty-five percent of the patients had continuing or recurrent disease, and 8.2% died from cancer. Deaths occurred largely in patients with class III or IV disease. Cervical lymph nodes were associated with increased recurrences, but not increased deaths. Extrathyroidal invasion carried an increased risk of 5.8-fold for death, and distant metastases increased this risk 47-fold. Age over 45 yr at diagnosis increased the risk of death 32-fold. Tumor size over 3 cm increased the risk of death 5.8-fold. Surgical treatment combining lobectomy plus at least contralateral subtotal thyroidectomy was associated, by Cox proportional hazard analysis, with decreased risk of death in patients with tumors larger than 1 cm and decreased risk of recurrence among all patients, including patients in classes I and II, compared to patients who underwent unilateral thyroid surgery or bilateral subtotal resections. By chi 2 analysis, 131I ablation of residual thyroid tissue after operation was associated with decreased risk of recurrence in tumors larger than 1 cm and decreased risk of death in patients in classes I and II with tumors more than 1 cm in size. The data strongly support the use of more extensive initial surgery in class I and II patients with tumors more than 1 cm in size as well as postoperative radioactive 131I ablation of thyroid remnant tissue.

Graves' disease in severe combined immunodeficient mice.

Graves' disease (GD) is an autoimmune thyroid disorder involving an antibody (TSAb) directed against the TSH receptor (TSHR) producing thyroid stimulation. We have developed an animal model of GD by engrafting peripheral blood mononuclear cells or T cell lines plus autologous thyroid tissue into severe combined immunodeficient (SCID) mice. We xenografted Graves' thyroid tissue from six patients into six groups of SCID mice. Autologous PBMC and T cell lines reactive to recombinant human TSHR extracellular domain and non-TSHR lines were injected ip into the designated groups. In some of the studies, thyroid tissue was irradiated with 2000 rads before xenografting. Irradiation of xenografts induced thyroid tissue damage and release of thyroid antigens and hormones. Mice reconstituted with peripheral blood mononuclear cells or nonspecific T cell lines did not simulate GD. However, we achieved production of TSAb, elevation of serum T3, and TSAb-dependent survival and function of human Graves' thyroid tissue in SCID mice reconstituted with TSHR-specific T cell lines. We reconstituted SCID mice with PBMC and TSHR-specific T cell lines that recognized TSHR peptide 158-176. This may be in vivo evidence of the importance of peptide 158-176 as an immunodominant epitope on the TSHR extracellular domain.

Morbidity and mortality in follicular thyroid cancer.

The natural history and results of treatment have been analyzed in a group of 49 patients with follicular thyroid carcinoma who were followed for an average of 10.7 yr. Striking differences between the course of follicular thyroid carcinoma and the course of papillary carcinoma are evident. Deaths from cancer were double (16% for follicular), age at diagnosis was older, and age at death was younger. All deaths and recurrences happened within 13 yr, in contrast to the continued experience of deaths and recurrences in papillary cancer, even through 40 yr of observation. Adverse outcome correlated with extent of disease at diagnosis and with size of primary tumor, but did not correlate with vessel invasion, extent of capsule invasion, degree of dedifferentiation, extent of primary surgery, or radioactive iodide ablation. These observations are again in striking contrast to experience with papillary cancer. No patient with intrathyroidal disease who was under age 45 at diagnosis and with a primary tumor of less than 2.5 cm died. Our observations suggest that follicular cancer, even if apparently intrathyroidal, carries a high mortality rate in patients over age 45 or in those with tumors larger than 2.5 cm at the time of diagnosis and suggest that we must consider additional therapeutic measures in this group of patients, including larger radioiodine doses for initial therapy, external radiotherapy, and even possibly prophylactic chemotherapy.

Osteosclerosis in primary hyperparathyroidism.

Osteosclerosis in adults with primary hyperparathyoidism is rare; the usual skeletal manifestation, when presented, is diffuse osteropenia. We describe a patient with generalized osteosclerosis in association with primary hyperparathyroidism. The findings are documented by conventional and fine-detail radiography, absorptiometric bone mineral analysis, quantitative microradiography and histologic examination of bone. The unique features are contrasted with the manifestations recorded in a recently studied group of 87 hyperparathyroid patients. The data presented here support a causal relationship in this patient between parathyroid hormone excess and the development of densely sclerotic bones.

Feminizing Sertoli cell tumors in boys with Peutz-Jeghers syndrome.

We report the pathology findings in two cases of multicentric Sertoli cell testicular tumors in two young boys with probable Peutz-Jeghers syndrome. Four cases of such tumors occurring in boys with Peutz-Jeghers syndrome were previously reported. Each of the two boys reported in this paper had prominent gynecomastia, rapid growth, and advanced bone age. Serum levels of estradiol were markedly elevated. Anti-müllerian hormone was measured in the serum of one of the boys and was in the normal range for age. Bilateral orchiectomy was performed in each case because the neoplastic growth would most likely result in sterility, and curtailment of height potential was threatened from continued elevation of estradiol levels. Microscopically, greatly enlarged seminiferous tubules packed with ovoid Sertoli-like cells were present. Prominent eosinophilic basement membrane surrounded the tubules and intersected between the cells, forming hyalinized ovoid globules and microcalcifications. Ultrastructure revealed lamination of basement membranes surrounding adjacent cells, ovoid cells with abundant cytoplasm, and limited smooth endoplasmic reticulum. Studies of testicular tumor tissue from both cases revealed increased transcription of the aromatase cytochrome P450 gene using promoter II, the promoter directing aromatase expression in the normal ovary and testis. The levels of transcripts were comparable to corpus luteum, thus resulting in increased estrogen synthesis. Transcripts specific for placental-type aromatase promoters (I.1 and I.2) were not detected in significant levels in these tumors.

Angiomyolipoma with regional lymph node involvement and long-term follow-up study.

The first long-term follow-up study of a patient who had renal angiomyolipoma with regional lymph node involvement is reported. The absence of recurrence after 15 years favors the view that regional lymph node involvement represents a multicentric hamartomatous change and is not a metastasis from a malignant renal tumor.

Papillary clear cell carcinoma of the thyroid gland.

A case of an unusual papillary clear cell carcinoma of the thyroid gland is described. The patient expired 17 days after operative biopsy and thyroxine suppression. Special stains were helpful in differentiating renal cortical carcinoma and parathyroid malignant disease from primary papillary clear cell carcinoma of the thyroid. Ultrastructural features of this tumor may relate to the effects of thyroid stimulating hormone as well as the malignant nature of the tumor.

Transcatheter bronchial brush and forceps biopsies. Histologic evaluation.

The histologic findings in transcatheter brush and forceps biopsies from 472 cases over a six-year period are evaluated. Diagnostic accuracy based on histologic findings was 38% and based on cytologic findings was 70%. When the two methods of examination were used, however, the overall accuracy was improved to 76%. In Hodgkin's disease and some inflammatory processes histologic examination is essential for the diagnosis. The transcatheter biopsies under fluoroscopic control are especially useful for securing tissues from the peripherally located lesions. When possible, examination of tissue obtained by transcatheter as well as forceps biopsies is encouraged.

The use of collagen-GAG membranes in reconstructive surgery.

Porous collagen-glycosaminoglycan (PCG) membranes with a porous silicone elastomer coating have been useful as a scaffold for dermal replacement in burn victims. Critical physicochemical parameters of these membranes include pore size, cross-link density, the percentage of glycosaminoglycan, and the degree of banding of the collagen. These factors govern the immunobiological response. Optimizing these parameters can reduce inflammation, scarring, and contraction of wounds grafted with PCG membranes. PCG membranes are currently commercially manufactured (Integra, Integra Life Sciences, New Jersey) and available for clinical use. Because clinical outcomes have improved using these membranes for burn wound coverage, other skin reconstruction problems including scar resurfacing, keloids, treatment of donor sites, and treatment of chronic wounds can be considered as potential applications. This manuscript illustrates our early experience using Integra as a CG membrane for dermal replacement in reconstructive surgery. Our results indicate that CG membranes can lead to improved compliance and appearance compared to a meshed graft and may be sequentially placed in multiple layers to correct contour deformities. Also, in one case, we observed that, if placed on a wound bed with embedded skin epithelial cells, the PCG promotes epithelialization through the PCG matrix. The use of this material results in a supple integument with many similarities to normal skin.

N-ras 61 oncogene mutations in Hürthle cell tumors.

Mutations of ras oncogenes are believed to play an important role in the initiation or progression of human tumors. In thyroid tumors the incidence of ras activation by specific point mutations has been reported to range from 33% in follicular adenomas up to 60% in anaplastic carcinomas. Because of our long-standing interest in Hürthle cell tumors, we began a study of 70 such cases to determine the incidence of ras mutations and their clinical correlates. Analysis of N-ras sequences at codon position 61, with the polymerase chain reaction method and oligonucleotide probe hybridization, showed point mutations of the normal codon CAA* in eight tumor samples. One was a mutation from CAA to AAA, one from CAA to CTA,* and six from CAA to CGA. These mutations would result in amino acid substitutions of lysine, leucine, or arginine for the normal glutamine at position 61 in the N-ras protein. Identical ras mutations in two tumors and some of their surrounding thyroid tissue may indicate that activating ras point mutations are an early event in carcinogenesis. The incidence of mutations was 1 of 24 (4%) of the histologically benign tumors, 5 of 34 (15%) of the intermediate tumors (with vascular or capsular permeation), and 2 of 12 (17%) in the malignant group. Four of these eight patients died of metastatic thyroid disease and four are alive without evidence of recurrence.

Coexisting thyroid and parathyroid disease--are they related?

A high prevalence of non-C cell, thyroid gland disease associated with primary hyperparathyroidism (HPT) has been reported in 11 uncontrolled studies. Yet experimental evidence linking these thyroid and parathyroid gland lesions is lacking. To test the hypothesis that the coexistence of these lesions is significant, we analyzed 124 consecutive cases of parathyroidectomy (110 women, mean age 53.5 +/- 12.7 years). Patients in the group with HPT who had visible or palpable thyroid disease at the time of operation were age-, sex-, and race-matched with autopsy controls. There was no statistical difference in the prevalence of total macroscopic thyroid lesions between the autopsy control group (46.4%) and the group of patients with HPT (54%, P = 0.8). Microscopic lesions in the absence of macroscopic abnormalities were found in an additional 26% of the autopsy control patients. Since in the surgical group, only those with macroscopic abnormalities underwent thyroid biopsy, no accurate calculation can be made of the microscopic lesions in those 55 patients with HPT who did not have macroscopic abnormalities. There was no difference in the prevalence of autoimmune or thyroid nodular disease between the two groups except for the presence of seven macroscopic nonmedullary thyroid carcinomas in the HPT group and none in the autopsy control group (P less than 0.001). One microscopic carcinoma was found in the autopsy group, however. An increased prevalence of parathyroid adenomas in nonmedullary thyroid disease has been suggested by other studies. We were unable to confirm this association. In fact, the incidence of parathyroid adenomas found unsuspectedly in 229 consecutive thyroidectomies was 0.43%. Thus with the exception of macroscopic, nonmedullary carcinomas, there was no evidence that thyroid disease accompanies HPT. Furthermore, parathyroid adenomas were not more frequent in surgical thyroid disease. Lesions of the thyroid and parathyroid glands are prevalent in middle-age women. This probably is the major factor that accounts for their coexistence.

Five cases of parathyroid lipohyperplasia.

Lipoadenoma is the accepted diagnosis of a single enlarged parathyroid gland that contains large quantities of mature fat cells and focal myxoid stroma, all widely separating small parenchymal cell nests in patients with hyperparathyroidism. Here we are reporting, for the first time, on five cases of hyperparathyroidism in which all four parathyroid glands are enlarged and each gland is noted to have an admixture of fat and parenchymal cells. We will introduce the descriptive diagnosis of lipohyperplasia to name this condition and keep it in perspective with other forms of parathyroid disease. All five patients were women between the ages of 36 and 62 years who underwent neck exploration, at which time four enlarged light-tan parathyroid glands were observed. Three and one half gland resections were performed, and all patients returned to a normocalcemic state except one who had borderline serum hypercalcemia after operation. Most of the resected parathyroid glands weighed in the range of 100 to 200 mg. The largest measured gland weighed 820 mg. Parathyroid histology showed an admixture of mature fat cells with parathyroid parenchymal cells often in a 1:1 ratio. One patient who had renal failure exhibited a lower ratio of fat cells. Two patients had chronic lymphocytic thyroiditis that was severe enough to require synthetic thyroid hormone therapy. Two patients had a history of urinary tract infections. Three patients had hypertensive cardiovascular disease, and several patients had arteriosclerotic cardiovascular disease. One patient had diabetes mellitus, one had a history of pituitary adenoma, and one had polydipsia. All of these patients were first seen with parathyroid glands measuring an average of five times normal size, yet they showed the usual 50% fat/50% parenchyma pattern of normal mature parathyroid glands. This means that the enlarged glands contain a 500% increase in parathyroid tissue, justifying the diagnostic term "lipohyperplasia." This easily represents enough parathyroid tissue to generate excessive parathyroid hormone production. At this time, there is no explanation of the pathogenesis of lipohyperplasia or how it varies from other previously described forms of parathyroid hyperplasia.

Comparison of mutations of ras oncogene in human pancreatic exocrine and endocrine tumors.

BACKGROUND: Ras oncogene mutations have been found in many human cancers; however, pancreatic endocrine tumors have rarely been studied. The purpose of this study was to analyze ras mutations in pancreatic endocrine tumors and to compare these results with the incidence of ras mutations in pancreatic exocrine cancers studied in our laboratory. METHODS: Ras oncogene mutations were studied in 33 foregut endocrine tumors (pancreatic 31, duodenal submucosa 2). Eleven were insulinomas, 12 gastrinomas, 2 glucagonomas, and 11 others were nonfunctioning islet cell carcinomas. Thirteen were benign and 20 were malignant. These were compared with 65 pancreatic exocrine cancers. Tumors were microdissected from paraffin-embedded sections. DNA was extracted and amplified by polymerase chain reaction. Mutations were detected by a oligonucleotide hybridization method with sequence-specific phosphorus 32-radiolabeled probes. RESULTS: No ras mutations were identified among the 33 pancreatic endocrine tumors. In contrast, 51 of 65 (78.5%) pancreatic exocrine cancers exhibited a ras mutation. Fifty were K-ras mutations and one unusual tumor exhibited a N-61 ras mutation. CONCLUSIONS: Ras oncogene mutations do not play a role in the tumorigenesis of pancreatic endocrine tumors.

Hürthle cell tumors: a twenty-five-year experience.

During a 25-year period (1959 through 1983), 54 patients with Hürthle cell tumors were treated and monitored at the University of Chicago Medical Center. Thirty percent were men and 70% were women; mean age at diagnosis was 46.7 +/- 13.2 years (range: 19 to 69 years). Tumors were grouped into three categories at the time of initial diagnosis: group 1, grossly malignant (four patients, or 7.5%); group 2, intermediate (partial capsular and/or subcapsular vascular invasion) (10 patients, or 18.5%); and group 3, benign appearing (40 patients, or 74%). Twenty-one (39%) of the patients had a history of low-dose, external radiation to the head and neck in childhood (including three of four grossly malignant lesions). A separate non-Hürthle cell thyroid carcinoma was found within the thyroid gland in 22 (50%) of the patients--79% were papillary and 21% were follicular carcinomas. In half of these, there was a history of childhood irradiation. During a mean follow-up period of 8.4 years (range, 22 days to 35 years), three additional Hürthle cell tumors were recognized as malignant after metastases were discovered--two were originally classified as intermediate lesions and one was in the benign-appearing group. Thus, seven of 54 of our patients (13%) had Hürthle cell carcinomas. One of the seven patients died of widespread metastases after 35 years, and the other six are currently free of disease. We believe that therapy of these lesions should be individualized. Total thyroid ablation (surgical procedure followed by radioiodine therapy) is appropriate for frankly malignant Hürthle cell cancers, for all Hürthle cell tumors occurring in patients who received low-dose childhood irradiation, for associated papillary or follicular carcinomas, and in those patients who exhibit partial capsular or subcapsular vascular invasion. On the other hand, single, well-encapsulated, benign-appearing Hürthle cell tumors may be treated by lobectomy and careful follow-up, since the chance that they will later exhibit malignant behavior is low (2.5% in our series and 1.5% among patients described in the recent literature).

Graves' disease and thyroid cancer.

The relationship between Graves' disease or its therapy and carcinoma of the thyroid remains uncertain. We studied 20 patients found to have thyroid cancer in glands previously treated for Graves' disease between 1961 and 1986 at the University of Chicago Medical Center. Sixteen (80%) occurred in women and four (20%) occurred in men. The mean age at operation was 37 years (range, 19 to 69 years) and did not differ by sex. Fifteen of the 20 cancers (75%) were papillary while five (25%) were follicular. Six individuals (30%) had a history of external radiation to the head and neck as an infant, child, or young adult. Two others had received radioiodine (RAI) therapy for Graves' disease 1 and 19 years earlier. Patients were divided into three groups: group I: four patients (20%) had a neck mass 4, 14, 20, and 41 years after having had a subtotal thyroidectomy (STT) for Graves' disease; three of four had a history of external irradiation therapy. These tumors behaved aggressively, resulting in the death of two of the four patients. group II: 11 patients (55%) had diffusely enlarge toxic goiters without a nodule. A carcinoma was diagnosed intraoperatively on frozen section in only two of these patients. The others received STT. After recognition on permanent section, those carcinomas that were 4 mm or greater in diameter received postoperative RAI. One recurrence occurred and was treated successfully with further RAI. group III: Five patients (25%) had Graves' disease and a palpable thyroid nodule. None of them had had a prior thyroidectomy for Graves' disease, as in group 1. Thyroid carcinoma was diagnosed in all patients preoperatively or intraoperatively, and a total thyroidectomy was performed. Each patient is alive and well with a mean follow-up of 5 years. Between 1971 and 1981, 194 patients had surgery for Graves' disease, and 10 (5.2%) were found to have an associated carcinoma; six patients (3.1% of the total) did not have a nodule or any other suspicion of malignancy before surgery. During the same time, 303 patients received RAI therapy for Graves' disease and one (0.3%) has subsequently developed thyroid carcinoma. Thyroid cancer associated with Graves' disease is found more commonly in surgically treated patients than in patients after RAI therapy. The greatest risk factor in our patients was previous external radiation to the head and neck. Such individuals should be treated with total thyroid ablation rather than the usual STT, since they are at risk of developing aggressive thyroid cancers if thyroid remnants are left.

Nuclear DNA analysis of insulinomas and gastrinomas.

The potential for malignancy of an islet cell tumor of the pancreas is difficult to cytologically judge when one evaluates only the primary lesion, because a malignant condition is usually determined by the presence of regional or distant metastases. Nuclear DNA cytometric measurements have proved helpful both in the evaluation of the malignant potential of other endocrine and nonendocrine lesions and in the determination of the "aggressiveness" of these tumors. Thirty-six islet cell tumors or their metastases from 25 patients were studied. Eleven patients had insulinomas and typical insulinoma syndromes, and 14 others had gastrinomas with the Zollinger-Ellison syndrome. Tissue from each tumor was stained by the Feulgen technique, and nuclear DNA cytometry was performed by means of the microTICAS system designed by the Cytopathology Laboratory of the University of Chicago. Ploidy measurements of insulinomas, taken alone, did not discriminate well between benign and malignant states. However, the single malignant insulinoma could be clearly recognized, for it was one of only two lesions in that group with 5N-exceeding rate (5N-ER) values of 1% or greater. (5N-ER is defined as the percentage of aneuploid nuclei with nuclear DNA content greater than 5N.) On the other hand, seven of eight malignant gastrinomas had ploidy values of 2.5N or greater (our definition of an aneuploid state) and/or had 5N-ER values of 1% or greater, while five of six benign gastrinomas had ploidy values of less than 2.5N and had 5N-ER values of 0%. In addition, the two most aggressive tumors had the highest ploidy and 5N-ER values. Nuclear DNA cytometric studies appear to offer promise as an aid in the evaluation of pancreatic islet cell tumors, particularly gastrinomas.