A Case of Pancreatic Nesidioblastosis with Aberrant Islet Cell Proliferation in a Beagle

J Toxicol Pathol 2004; 17: 55–58

Case Report A Case of Pancreatic Nesidioblastosis with Aberrant Islet Cell Proliferation in a Beagle

Toko Ohira1, Mayumi Ishizaki1, Seiki Yamakawa1, Hijiri Iwata1, Kiyoshi Imai1, and Makoto Enomoto1

1Department of Pathology, Biosafety Research Center, Foods, Drugs and Pesticides, 582–2 Shioshinden, Fukude-cho, Iwata-gun, Shizuoka 437–1213, Japan

Abstract: A 20-month-old female beagle showed a pancreatic nesidioblastosis with a curious proliferation of islet hormone-positive cells. These cells were characterized by a tubular or columnar pattern, occasionally with a rosette- like structure. Immunohistochemistry revealed that they were positive to insulin and chromogranin A and weakly- positive to glucagon and somatostatin in the cytoplasm, but negative for cytokeratin. PCNA- positive cells were also scattered among these proliferating cells. The present case appears to be a specific type of nesidioblastosis accompanied by a proliferation of previously unidentified islet-cells in a beagle. (J Toxicol Pathol 2004; 17: 55–58) Key words: nesidioblastosis, dog, insulin-positive, pancreas

Similar lesions to human nesidioblastosis in the glycogen in the blood was in a normal level (serum glucose: pancreas1 have been described in beagles2. Nesidioblastosis 91 mg/dl at 20 months of age). The dog was euthanized by is histologically characterized by irregular-shaped islet venesection under deep ether anesthesia. Gross postmortem structures showing a scattering proliferation of mixed observation at necropsy revealed only a small white patch in hypertrophic islet cells intermingled with so-called ductulo- the left lung and bile sediments in the gallbladder; no insular complex and atrophic acinar cells3–7. In abnormality existed in any lobe of the pancreas. nesidioblastosis of dogs, most of the abnormally Pancreas specimens from the middle body lobe and left proliferation islet cells are beta cells and small-sized lobes were fixed in 10% neutral buffered formalin, aggregates of the beta cells are frequently located in the embedded in paraffin, cut in 4 µm, and stained with vicinity of ducts or ductules. This lesion is regarded as a hematoxylin and eosin (HE), periodic acid-Schiff (PAS) regenerating change stimulated by the destruction of with diastase digestion, Alcian blue (pH 2.5), and silver exocrine tissue2. reticulin. Immunohistochemical staining was performed on The present case is a 20-month-old female beagle, some sections using a labeled streptavidin-biotinin method showing a specific type of nesidioblastosis accompanied by (DAKO, LSAB2 Kit, No.K0675, Carpinteria, CA). a curious focal proliferation of tubular or columnar cells with Polyclonal anti-insulin (DAKO, No.A0564), polyclonal islet-hormones production histologically. This dog, anti-glucagon (DAKO, No.A0565), polyclonal anti- obtained from Covance Research Products Inc., USA at 7 somatostatin (DAKO, No.A0566), polyclonal anti- months of age, was used as a control in one-year toxicity chromogranin A (DAKO, No.A430), monoclonal anti- study. This animal was housed in an aluminum cage (W 0.9 cytokeratin (DAKO, No.M0821), and monoclonal anti- × D 0.8 × H 0.75 m) in a conventional animal room under the proliferating cell nuclear antigen (PCNA) (DAKO, condition of air-controlled, temperature of 24 ± 3°C, and No.M0879) antibodies were used as primary antibodies. relative humidity of 55 ± 20%. Diets, commercial dog diet Biotinylated anti-mouse IgG (DAKO), anti-rabbit IgG TC-1 (Maruha Pet Food Co., Japan), and water were given (DAKO), and anti-guinea pig IgG were utilized as second ad libitum. The animal had neither abnormal clinical sign antibodies. nor abnormal data in hematology or blood chemistry; Other pancreatic tissues from 10 dogs, 6 males and 4 females from Covance Research Products Inc., 20 months of Received: 17 July 2003, Accepted: 16 January 2004 age with regular nesidioblastosis were histologically and Mailing address: Toko Ohira, Department of Pathology, Biosafety immmunohistochemically examined in the same way as Research Center, Foods, Drugs and Pesticides, 582–2 Shioshinden, described above for comparison with the present case. Fukude-cho, Iwata-gun, Shizuoka 437–1213, Japan The pancreatic lesions of the present case exhibited two TEL: 81-538-58-1266 FAX: 81-538-58-1343 structural patterns consisting of a regular nesidioblastosis E-mail: [email protected] 56 Aberrant Tubular Nesidioblastosis in Dog

Fig. 1. The pancreatic lesions showed focal tubular proliferation in the pancreas. The cells had large nuclei localized near the cellular base but did not have any zymogen granule in their cytoplasm. H.E. stain. × 100 (insert at right upper side, magnified portion, × 400).

Fig. 2. Most of the tubular or columnar cells were positive for immunohistochemical stain with insulin. × 100 (insert at right upper side, magnified portion, × 400).

associated with irregularly shaped ductulo- insular complex The tubular or columnar cells had large nuclei localized near and a focal proliferation of aberrant tubular or columunar the cellular base, but did not contain any zymogen-like cells intermingled with nesidioblastosis-like changes. The granule in the cytoplasm (Fig. 1). Some of them showed a latter lesions contained the atrophic acinar cells in its rosette-like structure. No fibrosis was found around them. peripheral regions surrounded by the exocrine parenchyma. Reticulin fibers demonstrated by silver staining showed a Ohira, Ishizaki, Yamakawa et al. 57

Fig. 3. Islet- like cells in the ductulo-insular complex found in nesidioblastosis lesions of the present case showed positive immunoreactivity to insulin (1), glucagon (2), and somatostatin (3). × 200.

Fig. 4. Regular nesidoblastosis, as observed in 10 cases, showed a scattered proliferation of ductulo- insular complexes mixed with occasional acinar cells. H.E. stain. × 200. All ductal structures in the nesidioblastosis lesion showed negative immunoreactivity to insulin (arrow, inserted at right upper corner, × 400). continuity of these aberrant cells with the islet cells forming Immunohistochemically, most of the aberrant cells clusters or cord-like arrangements, but did not show any were positive for insulin (Fig. 2) and for chromogranin A. distinct separation from the duct or ductular elements of the The basal portion of the aberrant cells showed strongly exocrine pancreas. positive reactivity for insulin. Some of the aberrant cells 58 Aberrant Tubular Nesidioblastosis in Dog were weakly positive to glucagon and somatostatin. mixed presence as a focal lesion in the area of the regular Enlarged round or oval, clear islet-cells seen dispersed in the nesidiobalastosis not accompanied by fibrous capsule may typical ductulo-insular complexes in other nesidioblastosis represent rather a mere aberrant hyperplastic appearance of areas of the present case, showed positive reactions to primitive islet cells than neoplastic occurrence of endocrine insulin, glucagon, and somatostatin (Fig. 3). Neither cells. However, because of the lack of other documented inflammatory cell infiltration nor evident fibrosis was cases, the origin of these curious histological features may included in the areas of nesidioblastosis. Both focal remain unclear. proliferation area of aberrant cells and hypertrophic islet cell-like cells showing cluster or cord-like arrangements References contained scattering PCNA-positive cells with occasional mitoses and atypical nuclei. Cytokeratin was negative in 1. Laidlaw GF. Nesidioblastoma, the islet tumor of the these cells. pancreas. Am J Pathol 1938; 14: 125–139. All 10 cases with regular nesidoblastosis showed 2. Katsuta O, Tsuchitani M, and Narama I. Abnormal scattering proliferation of the ductulo-insular complexes and proliferation of pancreatic endocrine cells in beagle dogs. J infrequently, small- sized ductal structures. However, all Toxicol Pathol 1992; 5: 67–76. 3. Yakovac WC, Baker L, and Hummeler K. Beta cell these ductal structures were negative to insulin (Fig. 4), nesidioblastosis in idiopathic hypoglycemia of infancy. J glucagon, and somatostatin. Cytokeratin was only positive Pediatr 1971; 79: 226–231. in the ductal structure. Atrophic acinar cells, occasionally 4. Dahms BB, Landing BH, Blaskovics M, and Roe TF. along with apoptosis, were found in the area of Nesidiobalastosis and other islet cell abnormalities in nesidioblastosis and in the surrounding exocrine pancreas hyperinsulinemic hypoglycemia of childhood. Human parenchyma. Pathol 1980; 11: 641–649. As population of proliferative endocrine cells in canine 5. Karnauchow PN. Nesidioblastosis in adults without insular nesidioblastosis, there are usually no significant changes in hyperfunction. Am J Clin Pathol 1982; 78: 511–513. the number of beta or delta cells, but a decreased number of 6. Gould VE, Memoli VA, Dardi LE, and Gould SN. alpha cells on the contrary, an increased number of Nesidiodysplasia and nesidioblastosis of infancy: structural pancreatic polypeptide-positive cells are noted as compared and functional correlations with the syndrome of hyperinsulinemic hypoglycemia. Pediatric Pathol 1983; 1: with those in the normal pancreas of dogs2,8. The pancreas in 7–31. the present case appeared to be a rare canine nesidioblastosis 7. Goossens A, Gepts W, Saudubray JM, Bonnefont JP, Nihoul characterized by focal proliferation of aberrant cells showing F, Heitz PU, and Klöppel G. Diffuse and focal pancreatic hormone production, especially insulin. nesidioblastosis. A clinico- pathogical study of 24 patients However, biochemical analysis of the blood did not reveal with persistent neonatal hyperinsulinemic hypoglycemia. any hyperinsulinemic hypoglycemia, as reported in most of Am J Surg Pathol 1989; 13: 766–775. the human cases3,4,6,7. 8. Hawkins KL, Summers BA, Kuhajda FP, and Smith CA. Although increased PCNA-positive cells and Immunocytochemistry of normal pancreatic islets and occasional mitosis seen in the aberrant structure of the spontaneous islet cell tumors in dogs. Vet Pathol 1987; 24: present case may suggest their proliferative activity, their 170–179.