Acinar cell cystadenocarcinoma of human pancreas

Acinar Cystic Transformation of the Pancreas: Histomorphology and Molecular Analysis to Unravel its Heterogeneous Nature

Acinar cystic transformation (ACT) of the pancreas, previously called acinar cell cystadenoma, is a poorly understood and rare entity among pancreatic cystic lesions. This study aims to clarify its real nature. This research cohort included 25 patients with pancreatic ACT, representing the largest series in the literature. We describe their clinicopathological features and molecular profile using next-generation sequencing. ACT arose more often in women (F/M≃2:1), in the body-tail region, with a mean size of ~4 cm. At the latest follow-up, all patients were alive and disease free. Histologically, a typical acinar epithelium lined all cysts, intermingled with ductal-like epithelium in 11/25 (44%) cases. All the cases lacked any evidence of malignancy. Three ACT showed peculiar features: 1 showed an extensive and diffuse microcystic pattern, and the other 2 harbored foci of low-grade pancreatic intraepithelial neoplasia (PanIN) in the ductal-like epithelium. Next-generation sequencing revealed the presence of 2 pathogenic/likely pathogenic mutations in 2 different cases, 1 with ductal-like epithelium and 1 with PanIN, and affecting KRAS (c.34G>C, p.G12R) and SMO (c.1685G>A, p.R562Q) genes, respectively. The other case with PanIN was not available for sequencing. Overall, our findings support that ACT is a benign entity, potentially arising from heterogeneous conditions/background, including: (1) acinar microcysts, (2) malformations, (3) obstructive/inflammatory setting, (4) genetic predisposition, (5) possible neoplastic origin. Although all indications are that ACT is benign, the potential occurrence of driver mutations suggests discussing a potential role of long-term surveillance for these patients.

Cystic Lesions of the Pancreas: Differential Diagnosis and Cytologic-Histologic Correlation

CONTEXT.—

Pancreatic cystic lesions (PCLs) are very common, and their detection is increasing with the advances in imaging techniques. Because of the major implications for management, distinguishing between neoplastic and nonneoplastic PCLs is critical. Neoplastic cysts with potential to progress into cancer include mucinous PCLs (intraductal papillary mucinous neoplasms and mucinous cystic neoplasms) and nonmucinous cysts (solid pseudopapillary tumors, serous cystic neoplasms, and neuroendocrine tumors with cystic degeneration). Nonneoplastic cysts with no risk of malignant transformation include pseudocysts, retention cysts, lymphoepithelial cysts, cystic pancreatic lymphangioma, and duplication cyst/ciliated foregut cysts. The role of endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) cytology with cyst fluid analysis in the diagnosis of PCLs has evolved during the last decade; however, a definitive diagnosis on cytologic specimens is hampered by the sparse cellularity and can be challenging. EUS-FNA can play an important role to differentiate low-risk from high-risk pancreatic cysts and to distinguish between patients with cysts who need clinical follow-up versus those who require surgery.

OBJECTIVE.—

To provide an integrative approach to diagnose pancreatic cystic lesions using EUS-FNA cytology and cyst fluid analysis, along with clinical, radiologic, histologic, genetic, and molecular characteristics.

DATA SOURCES.—

The review and analysis of the latest literature describing pancreatic cystic lesions.

CONCLUSIONS.—

Accurate diagnosis of PCLs requires a multidisciplinary and multimodal team approach, including the integration of clinical findings, imaging, cytology, cyst fluid analysis, and molecular testing.

Acinar Cell Cystadenocarcinoma of the Pancreas

Acinar cell cystadenocarcinoma is a rare malignant epithelial neoplasm of the pancreas with a diffusely cystic, gross architecture in which the cysts are lined with neoplastic epithelial cells that demonstrate evidence of pancreatic exocrine enzyme production. This is the 10th case that has been reported in the literature. A 77-year-old male complaining of left hypochondrial pain was referred to our hospital for treatment of a pancreatic tumor. A huge, honeycomb-structured tumor was detected in the pancreatic tail. Distal pancreatectomy with total resection of the residual stomach and partial resection of the transverse colon were performed. Microscopically, there were variably sized cystic lesions in the tumor. Immunohistochemical examinations revealed that tumor cells were positive for alpha 1-antichymotrypsin and alpha 1-trypsin, showing that tumor cells had features of pancreatic acinar cells. Thus, the tumor was diagnosed as acinar cell cystadenocarcinoma. Herein, we report a rare case with acinar cell cystadenocarcinoma, which is the 10th case reported in the literature based on a PubMed search. We managed to resect the tumor completely by distal pancreatectomy with total resection of the residual stomach and partial resection of the transverse colon. The patient is still alive 26 months after surgery without any recurrence after 1 year of adjuvant chemotherapy with S-1.

Acinar Cell Carcinoma of the Pancreas: Overview of Clinicopathologic Features and Insights into the Molecular Pathology

Acinar cell carcinomas (ACCs) of the pancreas are rare pancreatic neoplasms accounting for about 1–2% of pancreatic tumors in adults and about 15% in pediatric subjects. They show different clinical symptoms at presentation, different morphological features, different outcomes, and different molecular alterations. This heterogeneous clinicopathological spectrum may give rise to difficulties in the clinical and pathological diagnosis with consequential therapeutic and prognostic implications. The molecular mechanisms involved in the onset and progression of ACCs are still not completely understood, although in recent years, several attempts have been made to clarify the molecular mechanisms involved in ACC biology. In this paper, we will review the main clinicopathological and molecular features of pancreatic ACCs of both adult and pediatric subjects to give the reader a comprehensive overview of this rare tumor type.

Primary pancreatic cystic neoplasms of the pancreas revisited. Part IV: rare cystic neoplasms

Primary pancreatic cystic neoplasms are being recognized with increasing frequency due to modern imaging techniques. In addition to the more common cystic neoplasms-serous cystadenoma, primary mucinous cystic neoplasm, and intraductal papillary mucinous neoplasm-there are many other less common neoplasms that appear as cystic lesions. These cystic neoplasms include solid pseudopapillary neoplasm of the pancreas (the most common rare cystic neoplasm), cystic neuroendocrine neoplasm, cystic degeneration of otherwise solid neoplasms, and then the exceedingly rare cystic acinar cell neoplasm, intraductal tubular neoplasm, angiomatous neoplasm, lymphoepithelial cysts (not true neoplasms), and few others of mesenchymal origin. While quite rare, the pancreatic surgeon should at the least consider these unusual neoplasms in the differential diagnosis of potentially benign or malignant cystic lesions of the pancreas. Moreover, each of these unusual neoplasms has their own natural history/tumor biology and may require a different level of operative aggressiveness to obtain the optimal outcome.

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

Acinar cystic transformation of the pancreas is also known as acinar cell cystadenoma (ACC), and this is an extremely rare benign lesion that was first described in April 2002. We report here on a case of a previously asymptomatic patient with pancreatic ACC and this was diagnosed by computed tomography (CT) and magnetic resonance imaging (MRI). To the best of our knowledge, there is no previous report concerning the CT or MRI features of ACC in the medical literature. We present here the CT, MRI and pathological findings of pancreatic ACC.

Acinar cell carcinoma of the pancreas with intraductal growth: report of a case

Acinar cell carcinomas (ACCs) of the pancreas are rare neoplasms, accounting for approximately 1% of all exocrine pancreatic tumors. This type of tumor is known to be aggressive, although the survival rates are somewhat better than they are for ductal carcinoma. The tumor tends to present nonspecific symptoms. It occurs in older patients, and jaundice is infrequent. This report presents a case of ACC of the pancreas with intraductal papillary growth and lymph node metastasis.

An algorithmic approach to the diagnosis of pancreatic neoplasms

CONTEXT

The pancreas gives rise to an array of distinct neoplasms that can be solid, cystic, or intraductal and can recapitulate the various lines of differentiation present in the normal gland.

OBJECTIVE

To develop an algorithmic approach to the diagnosis of pancreatic neoplasms that simplifies their pathologic evaluation.

DATA SOURCES

We reviewed literature related to the classification of pancreatic neoplasms on the basis of their gross, histologic, and immunohistochemical features.

CONCLUSIONS

By using a series of dichotomous decisions, the differential diagnosis of a pancreatic neoplasm can be narrowed, and in cases of the more common neoplasms, accurate classification can be achieved. Uncommon neoplasms not accounted for by this approach are also discussed, and the additional diagnostic information needed for complete pathologic reporting is presented.

Pancreatic cysts: pathologic classification, differential diagnosis, and clinical implications

CONTEXT

Cystic lesions of the pancreas are being recognized with increasing frequency and have become a more common finding in clinical practice because of the widespread use of advanced imaging modalities and the sharp drop in the mortality rate of pancreatic surgery. Consequently, in the past 2 decades, the nature of many cystic tumors in this organ has been better characterized, and significant developments have taken place in the classification and in our understanding of pancreatic cystic lesions.

OBJECTIVE

To provide an overview of the current concepts in classification, differential diagnosis, and clinical/biologic behavior of pancreatic cystic tumors.

DATA SOURCES

The authors' personal experience, based on institutional and consultation materials, combined with an analysis of the literature.

CONCLUSIONS

In contrast to solid tumors, most of which are invasive ductal adenocarcinomas with dismal prognosis, cystic lesions of the pancreas are often either benign or low-grade indolent neoplasia. However, those that are mucinous, namely, intraductal papillary mucinous neoplasms and mucinous cystic neoplasms, constitute an important category because they have well-established malignant potential, representing an adenoma-carcinoma sequence. Those that are nonmucinous such as serous tumors, congenital cysts, lymphoepithelial cysts, and squamoid cyst of pancreatic ducts have no malignant potential. Only rare nonmucinous cystic tumors that occur as a result of degenerative/necrotic changes in otherwise solid neoplasia, such as cystic ductal adenocarcinomas, cystic pancreatic endocrine neoplasia, and solid-pseudopapillary neoplasm, are also malignant and have variable degrees of aggressiveness.

Cystic neoplasms of the exocrine pancreas

The increasing use of radiological imaging has led to greater detection of small and asymptomatic cystic lesions of the pancreas. Most are resectable, but not all are neoplastic. This review provides an update on the histopathology, immunohistochemistry, molecular biology, pathogenesis and management of cystic neoplasms of the exocrine pancreas. These include the serous, the mucinous cystic, the intraductal papillary mucinous and the solid pseudopapillary neoplasms. Recently reported variants are described and very rare cystic variants of other pancreatic epithelial and mesenchymal neoplasms are briefly mentioned.

Intraductal and papillary variants of acinar cell carcinomas: a new addition to the challenging differential diagnosis of intraductal neoplasms

The recognition and differential diagnosis of pancreatic intraductal neoplasms (IN) have gained importance in the past few years, as the incidence of these tumors (especially intraductal papillary mucinous neoplasms-IPMNs) have risen to >10% of pancreatic resections, and their significance as precursors of invasive cancer is better appreciated. Acinar cell carcinomas (ACCs) are typically solid tumors; however, we have recently encountered 7 ACCs with either intraductal growth and/or a papillary/papillocystic pattern that could be mistaken for IN. The clinicopathologic features of these cases were studied. Four patients were male and 3 female, with a mean age of 59 and mean tumor size of 4.9 cm (as compared with 10 cm in conventional ACCs). Only 1 patient had metastasis at the time of diagnosis (as opposed to 50% in usual ACCs). In 5 cases, the tumors had nodular growth of sheet-forming acinar cells, some of which were within ducts, as evidenced by the polypoid nature of the process, partial ductal lining, and presence of small tributary ducts in the walls. In 3 cases, the tumor had papillary and/or papillocystic growth, at least focally. All cases had cystic areas. No mucin was identified. All expressed trypsin. Markers of ductal differentiation were either absent or focal. A minor endocrine component was present in 3. The main histologic findings that distinguished these tumors from IPMNs were the more sheetlike nature of the nodules (rather than villous or arborizing papillae), cuboidal cells, overall basophilia of the cytoplasm, prominent nucleoli, apical granules, intraluminal crystals or pale, acidophilic secretions (enzymatic condensations), and lack of mucin. In conclusion, some ACCs show intraductal growth or exhibit papillary patterns, which can mimic IN, especially IPMNs. In such cases, attention to morphologic details described above, and immunohistochemistry are helpful. The clinical significance of this variant is difficult to determine; however, it appears that the tumors are relatively small and metastasis at presentation is less common than typically seen in ACCs (1/7 vs. 50%).

Nonductal neoplasms of the pancreas

Although the majority of pancreatic neoplasms are infiltrating ductal adenocarcinomas or other neoplasms with ductal differentiation, neoplasms with acinar, endocrine, mixed, or uncertain differentiation constitute a diverse and distinctive group. The most common and best-characterized nonductal neoplasms are pancreatic endocrine neoplasm, acinar cell carcinoma, pancreatoblastoma, and solid pseudopapillary neoplasm. This review details the clinical and pathologic features of these nonductal neoplasms, highlighting diagnostic criteria including the use of specific immunohistochemical stains to define the cellular differentiation of the neoplasms.

Cystic lesions of the pancreas

Although cystic tumors of the pancreas are relatively rare, they constitute an increasingly important category. Advances in imaging and interventional techniques and the sharp drop in the mortality rate of pancreatic surgery have rendered pancreatic biopsies and resections commonplace specimens. Consequently, in the past two decades, the nature of many cystic tumors in this organ has been better characterized. The names of some existing entities were revised; for example, what was known as papillary-cystic tumor is now regarded as solid-pseudopapillary tumor. New entities, in particular, intraductal papillary mucinous neoplasm and its variants, such as oncocytic and intestinal subtypes were recognized. The importance of clinical and pathologic correlation in the evaluation of these lesions was appreciated, in particular, with regards to the multifocality of these lesions, their association with invasive carcinomas, and thus their 'preinvasive' nature. Consensus criteria for the distinction of these from the ordinary precursors of adenocarcinoma, the pancreatic intraepithelial neoplasia, were established. The definition of mucinous cystic neoplasms was refined; ovarian-like stroma has now become almost a requirement for the diagnosis of mucinous cystic neoplasia, and defined as such, the propensity of these tumors to occur in perimenopausal women became even more striking. The validity and clinical value of classifying the pancreatic cysts of mucinous type as adenoma, borderline, CIS and invasive have been established. Related to this, the importance of thorough sampling in accurate classification of these mucinous lesions was recognized. Greater accessibility of the pancreas afforded by improved invasive as well as noninvasive modalities has also increased the detection of otherwise clinically silent cystic tumors, which has led to the recognition of more innocuous entities such as acinar cell cystadenoma and squamoid cyst of pancreatic ducts. As the significance of the cystic lesions emerged, cystic forms of otherwise typically solid tumors were also better characterized. Thus, significant developments have taken place in the classification and our understanding of pancreatic cystic tumors in the past few years, and experience with these lesions is likely to grow exponentially in the coming years.

Pancreatic acinar cell carcinoma extending into the common bile and main pancreatic ducts

Acinar cell carcinoma (ACC) of the pancreas is relatively rare, accounting for only approximately 1% of all exocrine pancreatic tumors. A 69-year-old man was found to have a mass lesion measuring approximately 4 cm in diameter in the pancreatic head on ultrasound, abdominal dynamic CT, and percutaneous transhepatic cholangiography. Magnetic resonance cholangiopancreatography showed defect of the lower common bile duct (CBD) due to obstruction by the tumor cast. Histopathologically, the pancreatic head tumor invaded the main pancreatic duct (MPD) and CBD with extension into the CBD in a form of tumor cast. The tumor cells consisted of a solid proliferation with abundant eosinophilic cytoplasm and round nuclei in an acinar and trabecular fashion. A 55-year-old man with upper abdominal pain and nausea, had a cystic lesion approximately 3 cm in size in the pancreatic tail on CT. Histopathologically, the tumor was encapsulated by fibrous capsule and had extensive central necrosis with solid areas in the tumor periphery, and invaded with extension into the MPD in a form of tumor cast. The tumor cells resembled acinar cells in solid growths. Two resected cases of ACC with unusual tumor extension into the CBD and the MPD, respectively, are reported.

Pancreatic ductal adenocarcinomas with cystic features: neither rare nor uniform

Cystic tumors of the pancreas are uncommon but important because of their diverse pathology and biology. Their wide spectrum also includes cystic variants of otherwise solid tumors, such as cystic endocrine tumors, cystic acinar cell carcinomas and ductal adenocarcinomas with cystic changes. In this study, we screened pancreatic ductal adenocarcinomas and their variants for macrocystic changes and determined the nature of the cysts (neoplastic vs non-neoplastic). Of 483 tumors 38 (8%) had cystic features. The largest group consisted of 24 pancreatic ductal adenocarcinomas showing a large-gland pattern with small cysts whose diameter varied between 0.5 and 1.8 cm. The epithelial lining of these cysts was generally positive for CEA (83%) and/or MUC1 (71%) and MUC5AC (74%). p53 was positive in 57% of the cases. The second group of cystic tumors (8/483) showed degenerative cystic cavities with diameters ranging between 1 and 6 cm. This group consisted of poorly differentiated pancreatic ductal adenocarcinomas, undifferentiated carcinomas with or without osteoclast-like giant cells and one adenosquamous carcinoma. In the third group of cystic tumors there were four pancreatic ductal adenocarcinomas containing tumor-related retention cysts. Their epithelial cells were positive for MUC5AC, but negative for CEA, MUC1 and p53. The fourth group consisted of two pancreatic ductal adenocarcinomas showing closely attached pseudocysts caused by tumor-associated pancreatitis. The results indicate that a considerable number of pancreatic ductal adenocarcinomas and their variants display cystic features and must therefore be considered in the differential diagnosis of cystic neoplasms of the pancreas. Moreover, not all of the cystic structures we observed were neoplastic in nature. They may also represent non-neoplastic changes, such as retention cysts and inflammatory pseudocysts.

Acinar cell cystadenocarcinoma of the pancreas: Report of rare case and review of the literature

Most exocrine pancreatic tumors are of ductal origin, whereas acinar cell adenocarcinomas are unusual (1% to 2% of all exocrine pancreatic neoplasms). We recently found a cystic adenocarcinoma of the pancreatic body whose cells had the characteristics of acinar cells, which we term acinar cell cystadenocarcinoma. Macroscopically, this tumor consists of a large multilocular cystic mass with a pseudocapsule and a spongy appearance on the cut surface. Microscopically, the cysts are lined by a single layer of cuboid/columnar cells. The cytoplasm has the characteristics of acinar cells, with eosinophilic granules in the apex and prominent nucleoli. Immunohistochemically, the cells express alpha1-antitrypsin, trypsin, and lipase in their cytoplasm, thus confirming the acinar origin of the tumor. A review of the literature revealed only 5 other cases of this tumor reported since its first description in 1981. Follow-up data are available for 4 of these; all of the affected patients had metastases at presentation or a few months later, and 2 died of the disease, at 13 and 37 months after diagnosis. Although this variant of adenocarcinoma of the pancreas is not prognostically different from the classic solid type (few patients survive more than 5 years), we believe that it is important because of its extreme rarity.

Pancreatic panniculitis in a patient with an acinar cell cystadenocarcinoma of the pancreas

We describe a 60-year-old man with pancreatic panniculitis associated with arthritis and peripheral eosinophilia in whom the skin symptoms led to a diagnosis of an underlying acinar cell cystadenocarcinoma. The panniculitis involved initially the legs, but soon thereafter lesions developed on the trunk and upper extremities. In the literature, only 5 cases of pancreatic acinar cell cystadenocarcinoma have been reported, none of these in association with panniculitis.

Cystic neoplasms of the pancreas and tumor-like lesions with cystic features: a review of 418 cases and a classification proposal

Although cystic neoplasms and lesions of the pancreas are rare, they have attracted a great deal of attention because of their potential curability. Since, in recent years, several new entities have been identified, the relative frequency of the tumors and their classification need to be reevaluated. In a series of 1454 tumorous lesions of the pancreas collected between 1971 and 2003 in our surgical pathology files and consultation files, all cystic pancreatic neoplasms and tumor-like lesions were identified and typed both histologically and immunohistochemically. There were 418 cases (29%) showing cysts with a diameter ranging between 0.5 cm and 27 cm. Most common were solid pseudopapillary neoplasms (21%) and intraductal papillary-mucinous neoplasms (18%). When only the cystic neoplasms and lesions that had been resected in a single institution were considered, intraductal papillary mucinous neoplasms were the most frequent cystic neoplasms, while solid pseudopapillary neoplasms took fifth place behind ductal adenocarcinomas with cystic features, serous cystic neoplasms and mucinous cystic neoplasms. The most frequent cystic tumor-like lesions were pancreatitis-associated pseudocysts. New and rare entities that have recently been identified are mucinous nonneoplastic cysts, acinar cell cystadenomas and cystic hamartomas. Bearing in mind that figures from referral centers such as ours may be biased regarding the relative frequency of lesions, we concluded from our data that intraductal papillary-mucinous neoplasms are the most frequently occurring pancreatic cystic neoplasms, rather than solid pseudopapillary neoplasms. It was possible to classify all cystic lesions encountered in our files or described in the literature in a new system that distinguishes between neoplastic and nonneoplastic lesions, with further subdivisions into epithelial (adenomas, borderline neoplasms and carcinomas) and nonepithelial tumors. This classification is easy to handle and enables a distinction on the basis of clinical behavior and prognosis.

Pancreatic acinar cell carcinoma presenting as acute pancreatitis

BACKGROUND

Acinar cell carcinoma (ACC) is a rare pancreatic neoplasm, and its presentation with acute pancreatitis has not been reported previously.

CASE OUTLINE

A 70-year-old man presented with acute pancreatitis, and a spiral CT scan showed a 5-cm tumour in the body of the pancreas. Distal pancreatectomy was performed, and histological examination showed an ACC.

DISCUSSION

This is a newly reported mode of presentation for a rare pancreatic tumour.

Role of cytology in the diagnosis of cystic and intradcutal papillary mucinous neoplasms

Cytology may provide valuable information and is diagnostic in many cases, but it is limited by sampling difficulties. Performance of mucin stains and analysis of the cyst fluid for tumor markers, as described in the article on histology of cystic neoplasms elsewhere in this issue, increase detection of MCNs and IPMNs; however, as with any other laboratory test, the results of the cyst fluid cytologic analysis need to be assessed in light of the clinical and radiologic findings, particularly when the cytology is not completely diagnostic.

Nonmucinous cystic pancreatic neoplasms

This article discusses serous cystadenomas, the most common of the nonmucinous cystic lesions of the pancreas. These microcystic lesions were previously known as "glycogen-rich" cystadenomas because of the presence of glycogen within the cyst epithelium. A small percentage of these lesions are macrocystic, and it may be difficult to differentiate them from mucinous lesions; however, endoscopic ultrasound guided fine needle aspiration can provide diagnostic material from the cyst fluid. The second most common nonmucinous cyst, the islet cell tumor, is also discussed. These rare cystic tumors may or may not be accompanied by excess hormone production. The prognosis for the rare cystic tumors is good if they are resected successfully.

Unilocular acinar cell cystadenoma of the pancreas an unusual acinar cell tumor

We report an unusual case of acinar cell cystadenoma of the pancreas in a 52-year-old man treated for pulmonary adenocarcinoma. The lesion, located in the body of the pancreas, was revealed incidentally by abdominal computed tomography during follow-up for a pulmonary neoplasm. A left pancreatectomy was performed. The unilocular cystic lesion measured 5 cm and was lined by a single layer of columnar acinar cells with eosinophilic granular cytoplasm, faintly stained by periodic acid-Schiff. Immunohistochemical analysis showed the lining cells were positive for cytokeratin and trypsin, and electronic microscopy showed that they contained zymogen granules. Acinar cell tumors of the pancreas are rare and include acinar cell carcinomas, acinar cell cystadenocarcinomas, and acinar cell adenomas. We report a case of cystic acinar cell tumor of the pancreas with benign gross and histologic features that could be added to the list of cystic neoplasms of the pancreas as acinar cell cystadenoma.

Acinar cell cystadenoma of the pancreas: a new entity?

This report describes a newly observed cystic lesion of the pancreas showing acinar cell differentiation. The patients affected by this lesion included seven women and three men (age range 16-66 years). In six patients, all of whom were female and all but one of whom suffered from abdominal pain, the cystic lesions (diameters, 4-15 cm) were detected by imaging techniques and subsequently removed. In four patients the cystic lesions were incidental findings. Eight lesions occurred as unifocal, unilocular or multilocular cysts in the head (n = 6) or tail (n = 2) of the pancreas. One lesion was bifocal (head and tail) and another involved the entire pancreas. The cysts were only rarely connected with the pancreatic duct system, but with acinar structures. Their lining cells expressed pancreatic enzymes and lacked any cellular atypia or proliferative activity (Ki67 index <1%). For a follow-up period of 6-84 months all patients remained alive and well. Although a nonneoplastic nature cannot be fully excluded, we propose that this lesion, composed of well-differentiated acinar cells, may represent the benign counterpart of the well-recognized acinar cystadenocarcinoma. We therefore suggest the term acinar cell cystadenoma.

Acinar cell carcinoma of the pancreas with and without endocrine differentiation

BACKGROUND

Acinar cell carcinoma (ACC) is a rare pancreatic neoplasm, representing 1% of exocrine tumours and containing a variable endocrine component. Three recent cases of ACC are reported.

CASE OUTLINES

A 72-year-old man with painless obstructive jaundice had a 5-cm mass in the head of pancreas resected by Whipple's operation; histopathological examination showed a typical ACC. A 33-year-old man with weight loss and abnormal liver function had a dilated biliary tree but no mass on imaging. Pylorus-preserving pancreatoduodenectomy was performed, and histology showed a mixed acinar-neuro-endocrine tumour. A 56-year-old man with weight loss and a palpable mass had a 15-cm mass in the distal body of pancreas, which was resected en bloc with the spleen and adherent stomach; it was a cystic ACC.

RESULTS

Two patients are alive and free of disease at 30 months and 15 months, while the third patient with locally advanced disease died of myocardial infarction at 9 weeks.

DISCUSSION

Acinar structures are the hallmark of this neoplasm, which carries a better survival rate than ductal cancer. Surgical excision prolongs survival and offers the best chance of cure.

Pancreatic acinar cell carcinoma

Acinar cell carcinomas (ACCs) are rare neoplasms that represent less than 2% of all exocrine tumors of the pancreas. Although they occur more often in adults between the 5th and 7th decades of life, a few cases have been reported in children. Histologically, ACCs can resemble islet cell tumors, but they differ in their ultrastructural and immunohistochemical features. Although ACCs present a bland histology, they are highly malignant and the survival of patients with these tumors, even though better than that of those with ductal cell carcinomas, is generally poor.

Mucinous cystic tumors of the pancreas: clinicopathological features, prognosis, and relationship to other mucinous cystic tumors

The clinicopathological features of 56 patients with mucinous cystic tumors (MCTs) of the pancreas were studied. Particular attention was paid to the prognosis of MCTs and the relationship to their ovarian, hepatic, and retroperitoneal counterparts. To distinguish MCTs from pancreatic intraductal papillary-mucinous tumors, MCTs were defined as tumors lacking communication with the duct system and containing mucin-producing epithelium, usually supported by ovarian-like stroma. All 56 tumors occurred in women (mean age 48.2 years) and were preferentially (93%) located in the body and tail of the pancreas. In accordance with the WHO classification, MCTs were divided into adenomas (n = 22), borderline tumors (n= 12), and noninvasive and invasive carcinomas (n = 22). Survival analysis revealed the extent of invasion to be the most significant prognostic factor (p<0.0001). Malignancy correlated with multilocularity and presence of papillary projections or mural nodules, loss of ovarian-like stroma, and p53 immunoreactivity. Stromal luteinization with expression of tyrosine hydroxylase, calretinin, or alpha inhibin was found in 66% of the cases. We conclude that the biologic behavior of MCTs is predictable on the basis of the extent of invasion. The similarities (i.e. gender, morphology, stromal luteinization) between pancreatic MCT and its ovarian, hepatobiliary, and retroperitoneal counterparts suggest a common pathway for their development.

Intraductal oncocytic papillary neoplasms of the pancreas

We describe the clinical and pathologic features of 11 intraductal oncocytic papillary neoplasms of the pancreas, a hitherto unrecognized tumor. The patients were six men and five women, and most of the tumors were in the head (head: body/tail = 8:3). The mean patient age was 62 (range, 39-78), and the average tumor size was 6 cm. Grossly the tumors exhibited mucin-filled cysts containing nodular papillary projections. Dilated ducts communicating with the main tumor were sometimes noted. Microscopically the cystic structures appeared to represent dilated ducts containing intraductal tumor. The tumors were characterized by variably complex, arborizing papillary structures. The papillae had thin, delicate fibrovascular cores with focal myxoid changes and were lined by stratified oncocytic cells. Goblet cells and intra-epithelial mucin-containing lumina were present, the latter resulting in a characteristic cribriform pattern. The exuberance of the epithelial proliferation varied from case to case and between different regions within individual tumors; solid sheets of cells were often identified. Although the degree of cytologic atypia was not generally severe, the complexity of the architecture justified a designation of intraductal oncocytic papillary carcinoma in 10 of the 11 cases. In nine cases the tumor was entirely intraductal; one case exhibited focal microinvasion and another showed widespread invasive carcinoma, the invasive elements appearing cytologically similar to the intraductal papillary components. The oncocytic cells stained positively with phosphotungstic acid hematoxylin and Novelli stains. Immunohistochemically, all cases stained positively for B72.3, and five cases showed focal, weak luminal membrane staining for carcinoembryonic antigen. Ultrastructurally many of the cells were packed with mitochondria, and mucin was also identified. Seven patients were alive and free of tumor from 1 month to 3 years (average, 1 year) after resection. Two patients died postoperatively. The remaining two patients died with no evidence of disease at 2.5 and 5 years, the latter following a recurrence at 2.5 years. We conclude that intraductal oncocytic papillary neoplasm is a distinctive pancreatic tumor that is usually intraductal but may develop invasive carcinoma and should be treated with complete resection.

Fibrillary inclusions in neoplastic and fetal acinar cells of the pancreas

We report a case of pancreatic acinar cell carcinoma which contained a large number of pleomorphic inclusions with fibrillary internal structures and mature zymogen granules. To clarify the significance of fibrillary inclusions in the differentiation of acinar cells of the pancreas, we further investigated fetal pancreases (gestational weeks 16, 17, 19, 20 and 28). We found two types of inclusions: type A, corresponding to fibrillary inclusion of neoplastic acinar cells, was observed only in a 19-week fetus; type B showed a homogeneous density similar to that of zymogen granules. Type B was observed in all the fetuses after the 17th gestational week. Although the type A inclusion might be generated through a different mechanism than the type B inclusion, the appearance of a large number of fibrillary inclusions in neoplastic acinar cells may represent a transient form of zymogen granule.

Cystic tumors of the pancreas

Cystic neoplasms of the pancreas are relatively uncommon lesions that should not be confused with pancreatic pseudocysts. Guidelines for this differential diagnosis, the characteristics of the more common varieties, and the authors' experience with 130 cystic tumors are described.

Mucinous cystic tumor of the pancreas: an analysis of FNA characteristics with an emphasis on the spectrum of malignancy associated features

Previously, pancreatic mucinous cystic tumors were classified as either benign (cystadenoma) or malignant (cystadenocarcinoma). Descriptions of the fine-needle aspiration (FNA) findings of these neoplasms have heretofore emphasized malignant cytologic characteristics. In the following, we present a summary of a study of FNA characteristics from ten patients with cystic mucinous neoplasms, four of whom have correlating histologic material. In this study, we found a spectrum of cytologic features ranging from completely benign appearing to obviously malignant. We discuss cystic mucinous pancreatic tumors and the associated FNA findings helpful in diagnosis and categorization of these neoplasms. Also, we suggest the inclusion of a new entity in the mucinous neoplasm category.

Liver, gallbladder, extrahepatic bile ducts, and pancreas

BACKGROUND

The liver, gallbladder, bile ducts, and pancreas have a common embryologic origin; cancers that arise from these sites therefore are expected to share a similar spectrum of histologic types. These cancers are known for their extremely poor prognoses.

METHODS

Data from the Surveillance, Epidemiology, and End Results Program regarding the incidence, distribution of histologic types, stage of disease, and survival for cancers of the gallbladder (n = 4412), extrahepatic bile ducts (n = 3486), pancreas (n = 23,116), and liver (n = 6,391) were reviewed. The most common histologic types are discussed, and the frequency of rare types is reported.

RESULTS

The incidence of biliary cancer decreased, while the incidence of hepatic and pancreatic cancer rose slightly over the 15-year period from 1973 to 1987. Age and sex distributions varied by histologic type. Greater than 98% of pancreatic and biliary cancers were carcinomas, and adenocarcinoma (not otherwise specified) was the most common histologic type recorded. In the liver, hepatocellular carcinoma was the most common type, followed by intrahepatic cholangiocarcinoma. The overall 5-year relative survival rates for these cancers were very low: gallbladder, 12.3%; extrahepatic bile duct, 12.7%; liver 3.1%; and pancreas 2.5% (all stages combined, 1978-1986).

CONCLUSIONS

This review confirmed that these carcinomas are associated with a very poor outcome; however, survival was influenced by stage of disease and histologic type. In the gallbladder and extrahepatic bile ducts, papillary adenocarcinoma was associated with the best outcome of all histologic types, and in the exocrine pancreas, mucinous cystadenocarcinoma was associated with the best prognosis.

Filamentous inclusions in acinar cell carcinoma of the pancreas

Acinar cell carcinoma of the pancreas exhibits a spectrum of histologic appearances. Some tumors can be readily identified by light microscopy, but others resemble endocrine/neuroendocrine neoplasms. Ultrastructurally, though large zymogen granules of acinar cells are usually distinctive, the zymogen granules of neoplastic acinar cells are sometimes abnormally small, overlapping in size with the granules of endocrine/neuroendocrine neoplasms. Six cases of acinar cell carcinoma, two with a typical histologic appearance and four that resembled endocrine/neuroendocrine tumors, were studied ultrastructurally. In addition to zymogen granules and abundant rough endoplasmic reticulum, all cases of acinar cell carcinoma exhibited pleomorphic, membrane bound inclusions that contained filaments. Similar inclusions were not identified in islet cell or carcinoid tumors, and several findings indicate that the inclusions represent deranged zymogen granules. In the ultrastructural study of a pancreatic neoplasm with granules, these inclusions may provide a clue for the diagnosis of acinar cell carcinoma.

A rare case of serous cystadenocarcinoma of the pancreas

Serous cystadenocarcinoma of the pancreas, a rare disease, developed in a 63-year-old Japanese woman. Pathologic examinations of the pancreatic tumor at the subtotal pancreatectomy showed it to be serous cystadenoma with focal atypical lesions. Three years after the operation, however, metastatic liver nodules were found, and the histologic characteristics of these lesions were quite similar to those of the pancreatic neoplasm. Both primary and metastatic tumors were composed of multiple cysts separated by fibrous septa. The epithelium of cysts was cuboidal and had clear cytoplasm, which had positive results for periodic acid-Schiff (PAS) and negative results for PAS with diastase, Alcian blue, and mucicarmine. To the knowledge of the authors, serous cystic neoplasms of the pancreas have been uniformly benign in biologic behavior. Recently, however, serous cystadenocarcinoma of the pancreas has been reported as a new entity. The current case is the second reported case and might support the existence of serous cystadenocarcinoma of the pancreas.

Upper abdominal neoplasms: an introduction and selected references

The organs in the upper half of the abdominal cavity can give rise to a highly heterogeneous collection of neoplasms that encompasses a broad spectrum of clinical features, light microscopic appearances, immunostaining properties, and fine structure. Because of the anatomic proximity of the viscera in this region, the differential diagnosis of an upper abdominal mass may include consideration of tumors that arise from the stomach, duodenum, liver, kidney, adrenal, and pancreas. There are many distinctive ultrastructural features among the various tumors that can be used effectively by the diagnostic electron microscopist, but it is also important to take into account the considerable overlap in fine structure that occurs among different tumors and among similar tumors from different organs. In the session on upper abdominal neoplasms, the electron microscopic characteristics of the common tumors of each viscus were reviewed before the presentation of individual case studies that incorporated original observations and illustrated some unusual entities. The selection of cases that follows is inevitably small and arbitrary, but the cases demonstrate the contribution that electron microscopy can make in the study of an upper abdominal mass and illustrate some of the similarities that can be encountered among tumors of different organs.

Cystic neoplasms of the pancreas: a clinical and radiological study of eight cases

Four patients with benign serous cystadenoma, one with mucinous cystadenoma, and three with mucinous cystadenocarcinoma treated in the university hospital of Göttingen between 1985 and 1988 were investigated. The main initial symptoms of these cystic tumors were abdominal pain (7/8), weight loss (3/8), maldigestion (3/8), and palpable abdominal mass (3/8), while laboratory investigations revealed nonspecific alterations (elevated ESR, mild hypochromic anemia). CA 19-9 was elevated in two patients, one of whom had cystadenocarcinoma; CEA also was elevated in this patient only. In all cases size, localization, and cystic character of the tumors were shown clearly by sonography and computed tomography; fine needle biopsy helped to distinguish between serous and mucinous cystadenoma in four of six cases. Because of their malignant potential, total extirpation of mucinous cystic tumors is the treatment of choice, while serous cystadenomas are benign and therefore may be treated conservatively in uncomplicated cases or high-risk patients.

Cystic neoplasms and true cysts of the pancreas

As the spectrum of pancreatic cysts evolves, sped by the increasing utilization of CT scanning, it becomes apparent that the surgeon must gain information preoperatively about the family history, as well as the personal history of the patient. The presence of cysts in the liver or kidney should be sought. The relation of the lesion to the duodenum and biliary tract needs to be defined. The possibility that the "cyst" represents necrosis of a primary adenocarcinoma of the pancreatic duct should be considered prior to laparotomy. At the time of operation, biopsy of the cyst wall and frozen-section study are fundamental to a decision whether resection or drainage is the treatment of choice. Resection is generally the treatment of the cystic neoplasms, drainage the treatment of pseudocysts. The failure of the surgeon to distinguish between the two groups may be catastrophic. The true cysts and cystic neoplasms of the pancreas are rare lesions. The clinical and radiologic characteristics, the pathologic features, and the natural history of these lesions are not fully documented. Therefore, when they are encountered, the clinician who will carefully document their characteristics can make a contribution to our knowledge.