Islet cell tumors of the pancreas: clinical, radiologic, and pathologic correlation in diagnosis and localization.

Islet cell tumors are rare pancreatic or peripancreatic neoplasms that produce and secrete hormones to a variable degree. These tumors are best divided on clinical grounds into those that produce a recognizable, clinically evident endocrine syndrome (ie, functioning) and those that exhibit no clinical evidence of hormone production (ie, clinically silent). Clinically silent tumors produce symptoms due to mass effect because of their large size. They are often partially cystic or necrotic. Functioning islet cell tumors usually manifest earlier in the course of the disease because of the distinctive signs and symptoms of the associated endocrine syndrome. Clinically silent and functioning tumors cannot be histologically distinguished reliably even with the use of immunohistochemical stains. Insulinoma and gastrinoma, the two most common functioning lesions, are typically small homogeneous masses. Other functioning islet cell tumors include glucagonoma, somatostatinoma, vipoma, and adrenocorticotropic hormone-producing tumor. Larger tumors are associated with calcification, cystic degeneration and necrosis, and a more aggressive behavior (local and vascular invasion as well as distant metastases). There are many different techniques for detection and characterization of these lesions that are usually chosen according to the radiologist's experience and preference. Treatment and prognosis of these lesions depend on the hormone produced, their size, and their behavior.

Islet cell tumors of the pancreas: pathologic-imaging correlation among size, necrosis and cysts, calcification, malignant behavior, and functional status.

OBJECTIVE: The purpose of our study was to correlate the imaging and pathologic features of islet cell tumors with regard to tumor size, necrosis and cysts, calcification, malignant behavior, and functional status. MATERIALS AND METHODS: We retrospectively reviewed the clinical, pathologic, and imaging features of all 133 cases of pathologically proved islet cell tumors of the pancreas seen at the Armed Forces Institute of Pathology. Clinical data, including the patients' symptoms and serologic characteristics, were used to distinguish hyperfunctioning tumors (those causing symptoms related to elevated serum polypeptide levels) from nonhyperfunctioning tumors; hyperfunctioning tumors were divided further into insulin-producing and non-insulin-producing types. All patients had at least one cross-sectional imaging study, including CT (n = 118), sonography (n = 42), or MR imaging (n = 22). Clinical, pathologic, and imaging features were evaluated and correlated with tumor size, necrosis and cysts, calcification, local invasion, vascular invasion, metastases, and functional status. RESULTS: Islet cell tumors with areas of necrosis or cystic change found pathologically and on imaging studies (56/133) were larger (8.4 cm in mean transverse diameter) than homogeneous solid lesions (2.9 cm in mean transverse diameter) and were predominantly non-insulin producing (48/56) and nonhyperfunctioning (36/56). Of the 43 insulinomas, 35 were small (2.2 cm in mean transverse diameter), solid, and homogeneous. Larger size also was associated with calcification and malignant behavior, including local invasion, vascular invasion, and distant metastases. CONCLUSION: Our findings show that cystic and necrotic islet cell tumors are usually non-insulin-producing and nonhyperfunctioning neoplasms and larger than the typically solid and small insulinomas. Calcification, local invasion, vascular invasion, and metastatic disease are more commonly seen with larger neoplasms.