Post-obstructive cyst formation in pancreas and cystic acinar transformation: Are they same?

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.

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.

Postobstructive Cyst Formation in Pancreatic Duct affecting Surgical Approach

How to cite this article: Ezer A, Parlakgumus A. Postobstructive Cyst Formation in Pancreatic Duct affecting Surgical Approach. Euroasian J Hepato-Gastroenterol 2018;8(1):99-100.