Acinar cell cystadenoma (acinar cystic transformation) of the pancreas: the radiologic-pathologic features

Reappraising imaging features of pancreatic acinar cystic transformation: be aware of differential diagnoses

OBJECTIVES

Imaging features of pancreatic acinar cystic transformation (ACT) have been published. We aimed to describe the clinical and radiological characteristics of patients with a presumed pancreatic ACT diagnosis, reappraising the value of these published imaging criteria.

MATERIALS AND METHODS

Single-center retrospective study (2003-2021) of consecutive patients with a presumed diagnosis of ACT as suggested by the local expert multidisciplinary case review board. Patients without available imaging (CT or MRI) for review were excluded. Patients were classified into "certain" ACT (if ≥ 2 imaging criteria and no differential diagnosis) or "uncertain" ACT (if ≥ 1 imaging criteria and suggested differential diagnoses).

RESULTS

Sixty-four patients (35 males, [55%]) were included. ACT was considered "certain" for 34 patients (53%) and "uncertain" for 30 patients (47%). The number of ACT criteria did not differ between groups, with 91.2% of patients with ≥ 3 ACT imaging criteria in the "certain" group vs 93.3% in the "uncertain" group (p = 0.88). In the "uncertain" group, the main suggested differentials were branch-duct intraductal papillary mucinous neoplasm (18/30 patients, 60%), calcifying chronic pancreatitis (8/30 patients, 27%), both (three patients, 10%) and serous cystadenoma (one patient, 3%). Calcifications were significantly more frequent in the "uncertain" group (89% vs 63% in the "certain" group, p = 0.02).

CONCLUSION

Published ACT imaging criteria are frequently associated with features suggesting differential diagnoses. They appear insufficient to reach a final diagnosis in a subset of patients.

CLINICAL RELEVANCE STATEMENT

ACT displays a heterogeneous morphological imaging presentation challenging the non-invasive diagnostic work-up. Physicians' and radiologists' awareness of this entity is important to better understand its natural history and improve non-invasive diagnostic criteria.

KEY POINTS

The criteria to help diagnose ACT are frequently associated with features suggestive of differentials. The main alternatives suggested when ACT diagnosis was "uncertain" were branch-duct intraductal papillary mucinous neoplasm and calcifying chronic pancreatitis. Published ACT diagnostic imaging criteria can be insufficient for a definite non-invasive diagnosis.

Acinar Cystic Transformation of the Pancreas With Main Pancreatic Duct Dilation and Distal Pancreatic Atrophy

We report a rare case of a large, slowly progressive acinar cystic transformation (ACT) of the pancreas with main duct dilation and atrophy of the upstream pancreas. The diagnosis was made through endoscopic ultrasound-guided through-the-needle biopsy and histological identification of cuboidal acinar epithelium and characteristic immunohistochemistry findings. Distal pancreatectomy and splenectomy were performed because of elevated carcinoembryonic antigen levels, atypical cells on biopsy, and an increase in cyst size. Owing to the benign nature of this case, postresection surveillance was not necessary.

Comprehensive characterisation of acinar cystic transformation of the pancreas: a systematic review

AIMS

Acinar cystic transformation (ACT) of the pancreas is a rare pancreatic cystic lesion. Owing to its rarity, comprehensive histomolecular characterisation of this entity is still lacking. We aim to perform a systematic review on this controversial entity.

METHODS

We searched PubMed, SCOPUS and Embase through May 2023 to identify all studies on ACTs. Clinicopathological, immunohistochemical (IHC) and molecular data have been extracted and analysed.

RESULTS

Overall, there were 121 cases of ACTs in the literature. ACT had a female predominance (65.3% of patients), and a mean size of 4.8 cm. ACT was more often unifocal (71.9%) and multiloculate (61.2%). Histologically, the cysts were lined by an acinar epithelium, sometimes harbouring ductal-like areas (18.2%). In five cases (4.1%), an intralesional pancreatic intraepithelial neoplasia (PanIN) was reported. Preoperative diagnosis is challenging. After surgical resection, all patients were alive and disease free during follow-up except one patient who developed a second ACT after resection. By IHC, all lesions were positive for acinar markers; cytokeratin 7 and 8/18/19 were usually positive, and Ki-67 was invariably ≤3%. At the molecular level, three cases demonstrated genetic alterations: one showed multiple chromosomal gains, and other two harboured somatic mutations of KRAS and SMO genes (one mutation per case).

CONCLUSIONS

Globally considered, our findings demonstrated that ACT is a benign entity, without the need of surgical resection with the exception of symptomatic lesions. The rare occurrence of intracystic PanINs and driver mutations suggest considering follow-up if a preoperative diagnosis of ACT can be made.

Pancreatic Acinar Cystic Transformation: Familial Forms Do Exist

ABSTRACT

Pancreatic acinar cystic transformation (ACT) is a recently described entity of the pancreatic cysts' spectrum. It is a nonneoplastic pancreatic lesion, mostly asymptomatic, and is considered a rare disease, with less than 100 reported cases. Its benign nature and the absence of reported cases of malignant transformation or invasive lesions were a plea for a conservative approach. As a consequence, little is known about the pathogenesis of this lesion. No familial history of ACT has been previously described. Here, we report a familial case of 2 siblings with typical ACT imaging lesions giving evidence for familial aggregation. No obvious environmental exposure was identified as a potential risk factor for ACT development. No physiological data exist to suggest a congenital nature of these lesions, but for the first patient, the calcifications seem to have appeared with time. Further research, with high throughput sequencing technologies, may elucidate genetic polymorphisms explaining potential ACT familial phenotype. In practice, careful family history collection must be performed to identify a possible familial form of ACT when this diagnosis is proposed.

Congenital Acinar Cystic Transformation of the Pancreas with Proximal Jejunal Atresia and Hepatic Iron Overload: An Autopsy Case

Introduction: Acinar cystic transformation (ACT) of the pancreas is characterized by multiple cysts lined by dual ductal and acinar-type of epithelium. ACT is typically a disease of adulthood and has not been described in a neonate. Case report: Autopsy of this term 3-day old male demonstrated cystic transformation of the entire pancreas measuring 42 mm in its largest dimension. The main pancreatic duct was patent. The numerous variable-sized cysts were lined by both ductal (CK7-positive) and acinar (trypsin-positive) epithelium. Congenital hemochromatosis of the liver, complete proximal jejunal atresia, gangrene of the post-atretic jejunum, and subglottic stenosis were associated features. Discussion/Conclusion: ACT may occur in the neonate in association with other abnormalities.

Acinar Cystic Transformation of the Pancreas: Report of Three Cases

Acinar cystic transformation (ACT) of the pancreas is a rare non-neoplastic cystic lesion. It is most frequently observed in the head of the pancreas. Despite advances in radiologic imaging methods, preoperative diagnosis of acinar cystic transformation is difficult, it is often confused with other cystic lesions. Here, we report three cases of acinar cystic transformation, one of which showed diffuse involvement of the pancreas, and the remaining two were multilocular localized cystic lesions. We analyzed their histomorphologic and immunohistochemical features. The patients' ages ranged between 15 and 43 years and the ratio of females to males was 2:1. On microscopic examination, the cysts were lined by a single layer of flattened-cuboidal or columnar epithelial cells. The epithelial cells were diffusely positive with trypsin and keratin 7, but patchy with keratin 19. Due to its rarity and lack of radiologic and clinical awareness compared with other pancreatic cystic lesions, preoperative diagnosis of acinar cystic transformation is difficult and not definitive. All cases reported to date have been clinically benign and there is no evidence of recurrence or malignant transformation. The optimal treatment and whether to perform surgery remain controversial.

Pancreatic Acinar Cell Cystadenoma Mimicking Pancreatic Serous Cystadenoma

Acinar cell cystadenoma, also known as an acinar cystic transformation of the pancreas, is an exceedingly rare but benign pancreatic lesion. A 51-year-old woman was transferred to Inje University Busan Paik Hospital because of an 8 cm-sized calcified, multiseptated, and multilocular cystic mass in the pancreatic tail observed during abdominal CT performed at another hospital. The patient did not complain of abdominal pain or other symptoms, and her laboratory findings were normal. MRI showed that the cyst was not connected to the main pancreatic duct. A pancreatic serous cystadenoma was suspected, and a laparoscopic distal pancreatectomy was performed. The resected mass was composed of variable sized multilocular cysts with incomplete septa and focally lined by epithelium with acinar differentiation. The patient was diagnosed with acinar cell cystadenoma and is currently being followed up regularly. No complications or recurrences have been observed.

Fifteen-Year Follow-Up of a Patient with Acinar Cystic Transformation of the Pancreas and Literature Review

Acinar cystic transformation (ACT), also known as “acinar cell cystadenoma,” is a rare and newly recognized benign pancreatic cystic neoplasm. However, its true malignant potential remains unknown. Here, we report a case of ACT with 15-year follow-up. A 10-year-old female initially presented with abdominal pain and was found to have a cystic lesion in the region of pancreatic head on computed tomography scan. She underwent an exploratory laparotomy, and the intraoperative biopsy of the cyst wall showed a true pancreatic cyst without malignancy. Her symptoms subsequently resolved, and she was placed under close ultrasound surveillance. For the next fifteen years, the patient was asymptomatic without any complications and had a successful pregnancy. Surveillance showed the tumor grew in size from 4.2 cm to 6.2 cm in diameter. In the latest five months, she noted occasional abdominal pain. A pylorus-preserving pancreaticoduodenectomy was performed. The resected cystic lesion was multilocular and lined by a single layer of bland epithelium ranging from nondescript flat/cuboidal epithelium to apparent acinar cells which were strongly positive for trypsin, so the final diagnosis was confirmed to be ACT. The prior biopsy was retrospectively reviewed to reveal similar epithelial lining. To the best of our knowledge, this is the longest period of follow-up for ACT to date. Our findings suggest that ACT is a slow-growing neoplasm without malignant transformation after fifteen years. Therefore, we recommend biopsy for histologic diagnosis followed by close ultrasound surveillance without surgical intervention in asymptomatic or young ACT patients.

Acinar cystic transformation of the pancreas: Report of a case and a review of the literature

Acinar cystic transformation (ACT) is a rare cystic lesion of the pancreas lately reclassified as a non-neoplastic entity. This is a presentation of a case of ACT and a review of the literature. A systematic PubMed search was conducted, yielding a result of 24 publications. Including our case report, 75 cases of ACT have been reported in the literature. The patients are mainly females with initial symptoms of abdominal pain. The cysts are primarily located in the head of the pancreas and are often multilocular on cross section and have a mean size of 53.2 mm. Microscopically, the cysts are lined by an acinar epithelium with abortive acinar formations. The cells are immunohistochemically positive in stains for trypsin, chymotrypsin and CK7. The Ki67-index is low; 1-2 %. No genetic alterations indicative of a neoplastic pathogenesis have been found. The mean follow up time is 37.4 months and no malignant transformation has been observed. A preoperative diagnosis is difficult to establish, but microbiopsies seem a promising tool. The indication for surgical intervention should be founded on the symptoms of the patients since no malignant transformation has ever been reported.

A resected case of symptomatic acinar cell cystadenoma of the pancreas displacing the main pancreatic duct

Acinar cell cystadenoma (ACA) of the pancreas has been newly recognized as an entity by the World Health Organization (WHO) definition (2010), and its pathogenesis has not been known adequately because of the rarity. Here, we report a case of a 22-year-old female who had been followed up for a cystic lesion at the tail of the pancreas pointed out by a screening computed tomography (CT) scan 7 years ago. The tumor grew in size from 3.3 to 5.1 cm in diameter for 6 years (0.3 cm per year). Particularly, it rapidly grew up to 6.3 cm in the latest 3 months in concurrence with the emergence of epigastralgia. A contrasted CT scan revealed the irregularly formed, multilocular cystic tumor having thin septum and calcification. The intratumoral magnetic resonance imaging intensity in the T1 and T2 weighted images were low and high, respectively. No communications between the tumor and the main pancreatic duct (MPD) were found, but the tumor displaced the MPD. She underwent surgical resection because the tumor was growing, turned symptomatic, and it seemed difficult to be diagnosed correctly until totally biopsied. Spleen-preserved distal pancreatectomy was performed. It was pathologically diagnosed as ACA; the cyst was lined by cells with normal acinar differentiation; cuboidal cells with round, basally oriented nuclei and eosinophilic granules in its apical cytoplasm. The abdominal pain has disappeared, and no recurrences have been found during a 5-year follow-up. Clinicians are recommended to consider an ACA as one of differential diagnoses of cystic tumors of the pancreas to provide appropriate diagnostics and therapeutics.

Acinar cell cystadenoma of the pancreas: A retrospective analysis of ten-year experience from a single academic institution

BACKGROUND/OBJECTIVE

Acinar cell cystadenoma (ACA), also referred to as "acinar cystic transformation", is a rare and newly recognized cystic lesion of the pancreas displaying apparent acinar cell differentiation with benign outcomes. We summarized our experience with the diagnosis, clinicopathologic feature, treatment and prognosis of ACA to provide a reference for the disposal of this uncommon condition.

METHODS

We retrospectively analyzed the clinical data from eight patients with ACA treated in our hospital between March, 2005 and January, 2015.

RESULTS

Among eight patients, five of whom were female and the age at diagnosis ranged from 33 to 67 years (mean, 49.8 y). The most commonly clinical symptom was abdominal pain. Eight lesions were unifocal and either unilocular (n = 5) or multilocular (n = 3) with average size of 10.5 cm (range, 5.1-19.7 cm). All the patients were treated surgically and a definite diagnosis of ACA was obtained by the histopathological, histochemical and immunohistochemical tests. The length of stay range was from 11 to 17 days and there were no perioperative deaths. At a median follow-up of 57.3 months, all the patients were alive and there was no evidence of recurrence, distant metastasis or malignant transformation.

CONCLUSIONS

Appropriately preoperative differential diagnosis of ACA remains challenging and the final result is usually gained by the histopathology and immunohistochemistry. Although the origin of ACA is still contradictory, surgery is actively advocated as the most effective method for relieving the symptoms and preventing the tumor from local extension or malignant transformation so as to obtain an optimal long-term survival.

CT and MR imaging of multilocular acinar cell cystadenoma: comparison with branch duct intraductal papillary mucinous neoplasia (IPMNs)

OBJECTIVES

To describe CT and MR imaging findings of acinar cell cystadenoma (ACC) of the pancreas and to compare them with those of branch duct intraductal papillary mucinous neoplasia (BD-IPMN) to identify distinctive elements.

METHODS

Five patients with ACC and the 20 consecutive patients with histologically proven BD-IPMN were retrospectively included. Clinical and biological information was collected and histological data reviewed. CT and MR findings were analysed blinded to pathological diagnosis in order to identify imaging diagnostic criteria of ACC.

RESULTS

Patients with ACC were symptomatic in all but one case and were younger than those with BD-IPMN (p = 0.006). Four radiological criteria allowed for differentiating ACC from IPMN: five or more cysts, clustered peripheral small cysts, presence of cyst calcifications and absence of communication with the main pancreatic duct (p < 0.05). Presence of at least two or three of these imaging criteria had a strong diagnostic value for ACC with a sensitivity of 100% and 80% and a specificity of 85% and 100%, respectively.

CONCLUSIONS

Preoperative differential diagnosis between ACC and BD-IPMN can be achieved using a combination of four CT and/or MR imaging criteria. Recognition of ACC patients could change patient management and lead to more conservative treatment.

KEY POINTS

Four imaging findings are associated with acinar cell cystadenoma (ACC). Imaging could achieve differential diagnosis between ACC and BD-IPMN. Diagnosis on imaging would change patient management and avoid surgical resection.

Molecular analysis of pancreatic acinar cell cystadenomas: Evidence of a non-neoplastic nature

The biology of pancreatic acinar cell cystadenomas has not been clearly defined. However, a non-neoplastic process, caused by a cell differentiation failure leading to a cystic transformation, has been discussed, as well as a benign neoplastic lesion. Pancreatic acinar cell cystadenomas usually consist of thin-walled unilocular or multilocular cysts, and mural nodules have been described in two cases of a recent series. In one of these nodules, chromosomal imbalances were detected, which provided preliminary evidence for a neoplastic process. The aim of the current study was to further characterize the lesions by molecular analyses. In four cases without mural nodules, the clonality was assessed by performing mutational analyses within the highly variable displacement-loop region of the mitochondrial DNA. As a result, no closer correlation was identified between different foci within the tumors than between the tumors and adjacent normal pancreatic acinar tissue, indicating polyclonality of these lesions. Further molecular analyses revealed no mutations of the β-catenin and K-ras genes. In addition, no immunohistochemical evidence was identified for mutations of Smad4 or p53. In conclusion, the results of the current study demonstrated that pancreatic acinar cell cystadenomas are non-neoplastic lesions, with the potential exception of those rare cases with mural nodules.

Acinar cell cystadenoma of the pancreas: report of three cases and literature review

INTRODUCTION

Acinar cell cystadenoma (ACC) of the pancreas was first described as a distinct pancreatic cystic neoplasm in 2002.

METHODS

We have encountered three cases of ACC at our institution in addition to the 15 cases reported to date in the world literature. The gender distribution in the total cohort of patients with ACC slightly favored females (61 % female), and the median age was 49.5 years.

RESULTS

Almost half (53 %) of the cases were identified incidentally, while the remainder presented with abdominal pain. The median tumor diameter was 5 cm in size, and no patients have had documented disease recurrence or progression, even in the setting of an incomplete resection.

CONCLUSION

These findings suggest a relatively indolent biology, and that complete resections are curative. As we will show, surgical resection is warranted to treat symptoms and prevent local extension or malignant transformation.

Acinar cystadenoma of the pancreas: a clinicopathologic study of 10 cases including multilocular lesions with mural nodules

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.

Periampullary localized pancreatic intraepithelial neoplasia-3 (PanIN-3): evaluation with contrast-enhanced MR cholangiography (MRCP)

BACKGROUND

The early determination of premalignant lesions of pancreas can prevent unnecessary excessive surgical procedures and can reduce morbidity and mortality. Pancreatic intraepithelial neoplasia-3 (PanIN-3) is a preinvasive form of adenocarcinoma (carcinoma in situ). PanINs have not taken place in the literature of radiology yet, it should be considered in differential diagnosis of pancreatic cystic lesions.

CASE REPORT

A patient with preliminary diagnosis of chronic cholecystitis who had choledocolithiasis and periampullary pancreatic cyst detected by noncontrast-enhanced (NCE) and contrast-enhanced (CE) magnetic resonance cholangiography (MRCP) is presented. Pathological examination results of gallbladder and pancreatic cyst were reported as gallbladder adenocarcinoma and PanIN-3, respectively.

CONCLUSIONS

Pancreatic cystic lesions with thin septa which enhances slightly with the administration of contrast material may represent PanIN-3. In patients with cystic pancreatic lesion localized at periampullary region, using CE-MRCP together with NCE-MRCP could be useful in the evaluation of pancreatic cystic masses as well as other abdominal pathologies.

Primary retroperitoneal acinar cell cystadenoma

In this report, we describe a case of hitherto unreported primary retroperitoneal acinar cell cystadenoma that morphologically and immunophenotypically resembled pancreatic acinar cell cystadenoma. Pancreatic acinar cell cystadenoma is a very uncommon benign lesion characterized by acinar cell differentiation, the evidence of pancreatic exocrine enzyme production, and the absence of cellular atypia. Our case occurred in a 55-year-old woman presenting a 10-cm multilocular cystic lesion in the retroperitoneum thought to be a mucinous cystic neoplasm. At laparotomy, the cystic mass, which showed no connection with any organ, was completely resected with a clinical diagnosis of cystic lymphangioma. The diagnosis of retroperitoneal acinar cell cystadenoma was based on the recognition of morphological acinar differentiation, the immunohistochemical demonstration of the acinar marker trypsin, and the absence of cellular atypia. These peculiar features can be used in the differential diagnosis with all the other cystic lesions of the retroperitoneum.