Microcystic features at US: A nonspecific sign for microcystic adenomas ofthe pancreas

Microcystic adenoma of the pancreas is a benign tumor with no malignant pot ential and may not require surgery if it is asymptomatic. In the past, a ma ss containing more than six small (<2-cm) cysts at ultrasonography (US) has been considered to be diagnostic for microcystic adenoma. However, a retro spective study of 36 patients with focal or diffuse pancreatic lesions cont aining over six small cysts demonstrated that this finding can occur in a w ide variety of neoplastic and inflammatory lesions, most of which are malig nant. These lesions included adenocarcinoma (n = 18), mucinous cystadenocar cinoma (n = 2), islet cell carcinoma (n = 1), lymphoma (n = 1), sarcoma (n = 1), metastases (n = 2), pancreatitis (n = 4), and adenoma (n = 7). Thus, a finding of multiple small cysts in a pancreatic mass is not specific for microcystic adenoma, and if diagnosis is based on US findings alone, many m alignant tumors will be misdiagnosed as microcystic adenomas. Furthermore, computed tomography provides only limited assistance in this setting due to overlapping findings. Needle biopsy can be highly accurate in diagnosing b oth microcystic adenoma and other malignant lesions and should generally be performed for all lesions with the US features described earlier.