Acinar Cystadenoma of the Pancreas

Abstract

Pancreatic acinar cystadenomas (ACAs) are rare cystic lesions showing acinar differentiation with benign outcome. Although debated, ACAs are favored to be neoplastic and potentially the benign counterpart of acinar cystadenocarcinoma. We present the largest single institution series to date comprising 10 cases. The mean age was 49 years with a female predominance (M:F=1:2.3). Abdominal/flank pain was the most common presentation (n=6). Serum amylase/lipase and cyst fluid amylase were often elevated. All lesions had a benign outcome on follow-up (5 to 67 mo). The lesions were unilocular (n=3) or multilocular (n=7) with mean size of 3.8 cm (range, 2.9 to 5.0 cm) and 5.1 cm (range, 2.0 to 7.5 cm), respectively. Eight lesions were unifocal with locations as follows: head (n=2), head/neck (n=2), body (n=1), tail (n=1), predominantly extrapancreatic with a microscopic intrapancreatic component (n=1), and unspecified location (n=1). Two lesions were multifocal, involving the head/uncinate/body and pancreatic head, respectively. Two aspects of ACAs that may represent a diagnostic pitfall include the propensity for acinar epithelium to appear as nondescript flat/cuboidal epithelium (trypsin/chymotrypsin immunopositive) and epithelial heterogeneity, with focal mucinous and squamous epithelium, the latter particularly in multilocular variants. In addition, 2 cases with intracystic nodules were observed. Array comparative genomic hybridization performed on 1 of these cases showed multiple chromosomal gains involving 1p, 3p, 5q, 6p, 7q, 8, 10q, 11, 14, 20, and X. These findings provide preliminary evidence that ACAs represent a cystic neoplastic lesion.

Fine Needle Aspiration Cytology of Acinar Cell Cystadenoma of the Pancreas

“…Histomorphologically, both unilocular and multilocular ACCs are lined by a single or dual layer of epithelium that can range from flattened to cuboidal. The epithelial cells are cytologically bland with basally located regular nuclei that lack atypia or mitoses [2,3,4,5]. The cytoplasm shows at least focal evidence of acinar differentiation [2,3,4] in the form of apically located coarse, brightly eosinophilic zymogen granules.…”

“…The affected age ranges from 9 to 71 years, with a male to female ratio varying from 2:1 to 1:7 [1,2,3]. Some patients may present with abdominal pain and discomfort [3,4], while others are asymptomatic [4,5].…”

“…Grossly, ACCs can be either unilocular or multilocular [1,2,3,4,5,6]. The latter may involve the pancreas in a diffuse fashion [3,4].…”

“…Histochemically, acinar differentiation can be demonstrated with periodic acid-Schiff (PAS) stain. The zymogen granules stain bright magenta, and the staining is preserved with PAS stain with diastase pretreatment (PAS-D) [2,4,5]. In some cases, eosinophilic secretions can be demonstrated in the lumen [2,4].…”

“…Acinar-type epithelium can be intermixed with areas of ductal, mucinous and squamous epithelium. These changes are more common in multilocular ACCs [2]. Histochemically, acinar differentiation can be demonstrated with periodic acid-Schiff (PAS) stain.…”