Cellular hamartoma resembling gastrointestinal stromal tumor: a solid tumor of the pancreas expressing c-kit (CD117)

Abstract

Solid tumors of the pancreas are usually neoplastic. We report on two adult patients, each with a solid tumor of the pancreas that presented with an unusual histology and seemed to follow a benign course. The tumors, one located in the body and one in the tail, were well demarcated and composed of irregularly arranged but welldifferentiated acini and small intralobular and interlobular ducts embedded in predominantly hypocellular fibrotic tissue that contained fascicles of cytologically bland spindle cells. Islets were lacking, but immunohistochemical staining for chromogranin A and insulin revealed individual scattered insulin-producing cells distributed between acinar and ductal cells. The spindle cell component tissue showed coexpression of CD34, c-kit (CD117) and bcl-2. The follow-up (2 and 4 years) of the patients was uneventful. We propose to designate the tumors as 'cellular hamartoma resembling gastrointestinal stromal tumor.' Modern Pathology ( Keywords: pancreatic tumor; hamartoma; c-kit; CD34; bcl-2; differential diagnosis Well-demarcated tumor-like lesions in the pancreas are uncommon. They have been described under the term pseudotumor 1 or inflammatory pseudotumor. 2 Recently, we described a tumorous lesion that we termed pancreatic solid and cystic hamartoma. 3 Here we report on two further solid pancreatic tumors that have features in common with both hamartomas and gastrointestinal stromal tumors. Patients, materials and methodsThe cases were collected from the consultation files of the Department of Pathology of the University of Kiel, to which they had been submitted by the Department of Pathology in Dinslaken, Germany (case 1), and the Department of Pathology of the University of Coimbra, Portugal (case 2).In the first case, a 51-year-old man without clinical symptoms had a routine check-up, during which a mass, 3 cm in diameter, was detected by ultrasonography in the tail of the pancreas next to the splenic artery. This finding was confirmed by endosonography and CT. Laboratory tests were normal. As a result of the unclear nature of the tumor, abdominal surgery was performed with resection of the tumor.In the second case, a 54-year-old woman with slight abdominal discomfort was examined by ultrasonography, which revealed a well-demarcated tumor, 2 cm in diameter, in the body of the pancreas. A left-sided pancreatic resection was performed to remove the tumor. Both patients had an uncomplicated postoperative course and so far (2 and 4 years, respectively) have relapse-free follow-up.Representative 4 mm sections of formalin-fixed, paraffin-embedded tissue from both specimens were stained with hematoxylin and eosin (H&E) and periodic acid-Schiff. Immunohistochemical staining was performed using the standard avidinbiotin method against following antibodies: cytokeratin 8 (CAM 5

Positive immunohistochemical staining of KIT in solid-pseudopapillary neoplasms of the pancreas is not associated with KIT/PDGFRA mutations

“…41 It is also interesting to note that the stromal cells of a pancreatic hamartoma also coexpressed KIT and CD34. 42 Coexpression of KIT and CD34 is a feature of interstitial cell of Cajal of both the intestine and the pancreas. 10 In summary, in this study we investigated KIT expression by immunohistochemical staining in 50 histologically confirmed solid-pseudopapillary neoplasms of the pancreas.…”

Chronic pancreatitis, pseudotumors and other tumor-like lesions

“…Among the noninflammatory pseudotumors are ampullary adenomyoma, splenic heterotopia, lipomatous pseudohypertrophy and hamartoma. 135,136 The tumor-like lesions mainly include cystic changes (see article on cystic neoplasia) and duct changes (see article on ductal adenocarcinoma). …”

Multiple solid pancreatic hamartomas: A case report and review of the literature

“…Mass-forming pancreatitis which is associated with autoimmune pancreatitis, congenital arteriovenous malformation, intra-pancreatic accessory spleen, and others [13,14] . Solid pancreatic hamartoma was first reported by Pauser et al [9] to be pancreatic tumors that had features in common with both hamartomas and gastrointestinal stromal tumors. Pancreatic hamartomas are divided into two subgroups: solid and cystic lesion and solid lesion [9] .…”

“…Non-neoplastic tumor-like lesions in the pancreas are uncommon and include hamartoma [1][2][3][4][5][6][7][8][9][10][11][12] . Mass-forming pancreatitis which is associated with autoimmune pancreatitis, congenital arteriovenous malformation, intra-pancreatic accessory spleen, and others [13,14] .…”