Pancreatic Ducts as an Important Route of Tumor Extension for Acinar Cell Carcinoma of the Pancreas

Novel Insights Into Immunohistochemical Analysis For Acinar Cell Neoplasm of The Pancreas: Carboxypeptidase A2, Carboxypeptidase A1, and Glycoprotein 2

Acinar cell carcinoma (ACC) is a rare and highly malignant pancreatic tumor. Owing to histologic similarity, ACC is often difficult to distinguish from other solid medullary pancreatic tumors, particularly neuroendocrine neoplasm (NEN) and intraductal tubulopapillary neoplasm (ITPN). We aimed to identify new immunohistochemical markers commonly expressed in tumor cells with acinar cell differentiation and useful for both surgical and small biopsy specimens. Candidate molecules exclusively expressed in neoplastic or non-neoplastic acinar cells in pancreatic tissues with specific and available antibodies suitable for immunohistochemistry were selected. We selected carboxypeptidase A1 (CPA1), carboxypeptidase A2 (CPA2), and glycoprotein 2 (GP2), which were expressed in 100%, 100%, and 96% of cases, respectively, in ACC (n=27) or neoplasia with acinar cell differentiation, including mixed acinar-neuroendocrine carcinoma (n=9), mixed acinar-ductal carcinoma (n=3), pancreatoblastoma (n=4), and acinar cystic transformation (n=2), in the cytoplasm of tumor cells with a granular pattern. Both CPA2 and CPA1 were not expressed in any other tumors without acinar cell differentiation, including NEN (n=44), pancreatic ductal adenocarcinoma (n=44), and ITPN (n=4). GP2 was not expressed in these tumors except in rare cases, including 14% of NEN, 15% of intraductal papillary-mucinous neoplasm, 25% of intraductal oncocytic papillary neoplasm, 25% of ITPN, and 7% of pancreatic ductal adenocarcinoma, wherein a small proportion of tumor cells expressed GP2 in their apical cell membrane. NEN cases also showed cytoplasmic GP2 expression. Therefore, CPA2, CPA1, and potentially GP2 may act as ACC markers.

Pancreatic acinar cell carcinoma with predominant extension into the main pancreatic duct: A case report

A 34‐year‐old male was referred to our hospital for a possible pancreatic mass detected by computed tomography (CT) that was performed to find the cause of acute pancreatitis. Multiple imaging tests, including contrast‐enhanced CT scan, magnetic resonance imaging, contrast‐enhanced endoscopic ultrasonography, and endoscopic retrograde pancreatography, revealed a solid mass occupying the head of the main pancreatic duct (MDP), and pancreaticoduodenectomy was performed. In the resected specimen, the tumor showed expansive growth from the pancreatic parenchyma to the MDP and formed a tumor plug. Histopathological findings together with immunostaining findings led to the diagnosis of pancreatic acinar cell carcinoma (PACC). The patient was alive and recurrence‐free for 11 years after surgery. Extension into the MDP is more common in PACC than in conventional pancreatic ductal adenocarcinoma. PACC patients with MDP extension may have less aggressive clinicopathologic characteristics, and a relatively good prognosis can be expected.

A resected case of focal autoimmune pancreatitis with pancreatic duct wall thickening representing periductal lymphoplasmacytic infiltrate

This case revealed that branch pancreatic duct wall thickening by endoscopic ultrasonography represented periductal lymphoplasmacytic infiltrate as a characteristic histopathological finding of autoimmune pancreatitis, which may help in the diagnosis of autoimmune pancreatitis. An 80-year-old man was referred because fluorodeoxyglucose-positron emission tomography for lung cancer indicated abnormal uptake in the pancreatic head. Computed tomography showed an enhanced mass with cystic structures in the pancreatic head. Magnetic resonance cholangiopancreatography revealed mild dilatation of the main pancreatic duct in the pancreatic body with no strictures. Endoscopic ultrasonography demonstrated a lobulated heterogeneous hypoechoic mass in the pancreatic head. A branch pancreatic duct with wall thickening connected the mass to the main pancreatic duct. An intraductal neoplasm filling and spreading into the branch pancreatic duct was considered, and surgery was performed. Histopathologically, the mass consisted of marked inflammatory cell infiltration, storiform fibrosis, and obliterative phlebitis. The branch pancreatic duct with wall thickening revealed a band-like inflammatory cell infiltration with mainly lymphocytes and plasma cells beneath the normal pancreatic duct epithelium. Immunohistological staining revealed abundant IgG4-positive plasma cells (> 10 cells/HPF) in the inflammatory cell infiltration. The definite diagnosis was type 1 focal autoimmune pancreatitis.

Pancreatic Neoplasms With Acinar Differentiation: A Review of Pathologic and Molecular Features

CONTEXT.—

Pancreatic acinar lesions encompass a broad spectrum of malignant tumors and benign reactive processes affecting both adults and children, with clinical, pathologic, and molecular features that are distinct from more common ductal neoplasms. Accurate morphologic diagnosis and molecular assessment of these uncommon neoplasms is critical for effective patient care.

OBJECTIVE.—

To review the clinical, pathologic, and molecular features of pancreatic neoplasms with acinar differentiation, the most common of which is acinar cell carcinoma but which also includes mixed carcinomas with acinar components, cystic acinar lesions, and pancreatoblastoma.

DATA SOURCES.—

We assessed the current primary literature, as well as recently updated diagnostic manuals.

CONCLUSIONS.—

Pancreatic acinar neoplasms are a morphologically and molecularly heterogeneous group of diseases that are characterized by acinar differentiation of at least a subset of the neoplastic cells, defined either morphologically (granular cytoplasm, single prominent nucleoli) or immunohistochemically. Squamoid nests are a key morphologic feature of pancreatoblastoma. Alterations in WNT signaling and chromosomal 11p loss are common molecular features of both acinar cell carcinoma and pancreatoblastoma. Targetable molecular alterations in acinar carcinoma include BRAF rearrangements and DNA repair defects, including mismatch repair deficiency and BRCA pathway defects. For practicing pathologists, morphologic recognition of such acinar neoplasms is critical, and in the future, molecular diagnostics to identify lesions susceptible to targeted therapy will likely form an important component of patient care.

Pancreatic acinar cell carcinoma with extension into the main pancreatic duct: a case report

Background

Pancreatic acinar cell carcinoma (PACC) is a rare exocrine malignant tumor. Its widespread intraductal extension into the main pancreatic duct (MPD) is also rare.

Case presentation

We report the case of a 71-year-old man with PACC with MPD extension. The patient was assessed with laboratory and radiographic investigations that facilitated a preoperative diagnosis. Endoscopic ultrasonography (EUS) and dynamic thin-slice multi-detector row computed tomography (MDCT) were useful for determining the resection line of the pancreas. EUS-guided fine needle aspiration (EUS-FNA) was also helpful in determining the tumor biology and treatment strategy. Distal pancreatectomy was performed. The MPD was occupied by the tumor 35 mm downstream and 5 mm upstream. Histopathologically, the pancreatic tail tumor extended continuously into the MPD. The tumor was solid with cells showing eosinophilic and granular cytoplasm, indicating the diagnosis of PACC. This is an interesting case of PACC with intraductal extension into the MPD. We discuss the possible mechanisms of tumor extension in this rare case together with a review of the literature.

Conclusions

We describe a rare pancreatic acinar cell carcinoma that could be adequately treated using preoperative precise imaging and histopathological evaluations. When an intraductal tumor extension in the MPD is encountered, the diagnosis of a rare pancreatic tumor should be considered, as in our case.

A case of intraductal tubulopapillary neoplasm of the pancreas in a branch duct: a rare case report and literature review

BACKGROUND

Intraductal tubulopapillary neoplasm (ITPN) of the pancreas is a new disease concept defined by the World Health Organization in 2010. ITPN progresses with tubulopapillary growth in the pancreatic duct and is known to have a fair prognosis. Localization in the main pancreatic duct (MPD) is one characteristic. There are few case reports of ITPN in a branch of the pancreatic duct (BD).

CASE PRESENTATION

We encountered a case of ITPN localized in BD. An 85-year-old man was followed after colonic surgery for rectal carcinoma. An abdominal computed tomography scan revealed a cystic mass in the pancreatic head and further examination was done. A T2 weighted intension picture in magnetic resonance imaging showed a 20 mm cystic lesion with an internal mass of 15 mm. Duodenal papilla were slightly open and endoscopic retrograde pancreatography revealed mild and diffuse dilatation of the main pancreatic duct and mucin in the MPD. In consideration with the image examinations, we diagnosed the tumor as an intraductal papillary mucinous neoplasm with carcinoma because of its large mural nodule (> 10 mm in size) in a cyst. Consequently, a pancreaticoduodenectomy was performed. Macroscopically, a white solid tumor sized 2.5 × 1.8 × 1.0 was identified in the head of the pancreas. The cut surface of the resected pancreas showed a side-branch type intraductal tumor with tubulopapillary architecture without mucin secretion. Immunohistochemical staining was positive for MUC1, and negative for MUC2 and MUC5AC. The final diagnosis was determined to be pancreatic ITPN from BD. At the time of this report (48 months post-surgery), the patient remains disease-free without evidence of recurrence.

CONCLUSION

ITPNs localized in BD are rare and diagnosis prior to surgery is difficult. In our case, the shape was round, not papillary, and with little fluid. These characteristics are different from a branch duct type IPMN and can be a clue to suspect ITPN in BD.

Type 1 Autoimmune Pancreatitis Extending along the Main Pancreatic Duct: IgG4-related Pancreatic Periductitis

We herein report a unique form of autoimmune pancreatitis (AIP) spreading along the main pancreatic duct (MPD). A 70-year-old man was referred for a small lesion at the pancreatic neck, accompanying an adjacent cyst and dilated upstream MPD. Four years earlier, health checkup images had shown a pancreatic cyst but no mass lesion. Endoscopic ultrasonography showed a contrast-enhanced, tumorous lesion, mainly occupying the MPD. With a preoperative diagnosis of ductal neoplasms mainly spreading in the MPD, Whipple's resection was performed. The resected specimens showed MPD periductitis with IgG4-related pathology, indicating type 1 AIP. Clinicians should practice caution concerning the various AIP forms.

Primary Pancreatic Yolk Sac Tumor Presenting as Diffusely Enlarged Pancreas in Initial 18F-FDG PET/CT

Yolk sac tumor is a rare and highly malignant germ cell tumor. We report a case of yolk sac tumor primarily in the pancreas in a 32-year-old man. He presented with pancreatitis at presentation with significantly increased serum alpha-fetoprotein (AFP). F-FDG PET/CT revealed diffuse enlargement of the pancreas in the neck, body, and tail portion with homogeneously increased FDG uptake, similar to the change of pancreatitis. The lesion progressively developed to a huge pancreatic mass in the follow-up images, and endoscopic ultrasonography-guided aspiration biopsy of the pancreatic mass confirmed the diagnosis of yolk sac tumor.

Intraductal dissemination of ampullary carcinoma after pancreatoduodenectomy

BACKGROUND

Clinical evidence of intraductal dissemination through the pancreatic duct has been rare. We herein describe a case of ampullary carcinoma that disseminated in the remnant pancreas through the pancreatic duct.

CASE PRESENTATION

A 68-year-old woman underwent SSPPD for ampullary carcinoma. The tumor was diagnosed as adenocarcinoma without lymph node metastasis (T2N0M0, stage IB). Computed tomography (CT) performed 3 years later revealed a 14-mm tumor near the site of the pancreaticojejunal anastomosis. Endoscopic ultrasound-guided fine needle aspiration showed adenocarcinoma that was morphologically similar to the specimen from the first surgery. We diagnosed recurrence of ampullary carcinoma in the remnant pancreas. A total remnant pancreatectomy was performed. We found a white solid tumor at the 20-mm distal side of pancreaticojejunal anastomosis. The tumor was morphologically similar and immunostaining showed a pattern identical to that of the original tumor, suggesting that the two tumors were of the same origin.

CONCLUSION

The recurrent lesion was most likely the result of tumor cells leaving the tumor and implanting in the remnant pancreatic duct epithelium. Intraductal dissemination of adenocarcinoma is thought to be a cause of remnant recurrence after SSPPD in cases of obstruction of the pancreatic duct or an iatrogenic procedure.

Intraductal Tubulopapillary Neoplasm of the Pancreas: An Overview

Intraductal tubulopapillary neoplasm is a rare tumor that the World Health Organization recognized in 2010 as a subtype of premalignant pancreatic neoplasms. It is important to distinguish it from other intraductal neoplasms, including intraductal papillary mucinous neoplasm, pancreatic ductal adenocarcinoma, and intraductal variant of acinar cell carcinoma, because intraductal tubulopapillary neoplasm has a favorable prognosis. Histopathologically, intraductal tubulopapillary neoplasms are characterized by tubulopapillary growth, uniform high-grade cytologic atypia, frequent necrotic foci, evident ductal differentiation, and absence of mucin. Intraductal tubulopapillary neoplasms show distinct immunohistochemical and molecular findings, with positive cytokeratin 7, cytokeratin 19, MUC1, and MUC6, and somatic PIK3CA mutations (2 of 11; 18%), and low rates of KRAS (2 of 20; 10%), TP53 (5 of 22; 23%), and BRAF (2 of 13; 15%) mutations. These differences also highlight the fact that intraductal tubulopapillary pancreatic neoplasm is distinct from other similar neoplasms.

Intrapancreatic recurrence of intraductal tubulopapillary neoplasm (ITPN) 16 years after the initial surgery for noninvasive ITPN: a case report

Background

Intraductal tubulopapillary neoplasm (ITPN) is a rare pancreatic intraductal neoplasm. It is characterized by a tubulopapillary growth pattern, entirely high-grade atypical cells, minimal cytoplasmic mucin, and no obvious luminal mucin secretion. Most of its biological nature remains unclear.

Case presentation

We herein report a case of intrapancreatic recurrence of ITPN in the remnant pancreas of a patient who underwent pancreatoduodenectomy 16 years previously for a noninvasive intraductal pancreatic head tumor. We reexamined the primary tumor and compared it with the most recently resected specimen. Histologically, the primary tumor showed a tubulopapillary growth of high-grade atypical cells with scanty cytoplasmic mucin, which was similar to the recently resected specimen except for the invasive area. Immunohistochemically, the neoplastic cells in both specimens showed focal staining of MUC1 and positivity for MUC6 but negativity for MUC2, MUC5AC, CDX2, and trypsin. Molecular analysis revealed no KRAS/GNAS/BRAF/PIK3CA mutations in either of the specimens.

Conclusions

These findings of the original tumor and recently resected tumor were compatible with the features of ITPN. Thus, recurrence is possible even for a primary noninvasive ITPN, and long-term surveillance is recommended.

Pathological and Molecular Aspects to Improve Endoscopic Ultrasonography-Guided Fine-Needle Aspiration From Solid Pancreatic Lesions

Endoscopic ultrasonography-guided fine-needle aspiration (EUS-FNA) has been applied to pancreatic lesions since the 1990s, and its use is now widespread. Improvements in endoscopic devices and sampling techniques have resulted in excellent diagnostic ability for solid pancreatic lesions. However, clinical improvements alone are not responsible for it; pathological aspects have also played important roles. Rapid on-site evaluation minimizes endoscopic procedures, although its value at improving the diagnostic ratio is still debated. Diagnostic efficacy differs by sample preparations (direct smear, cytospin, liquid-based cytology, cell block, and biopsy) and by staining methods (Papanicoloau, Diff-Quik, hematoxylin-eosin, and Giemsa). Several immunocytochemistry protocols aid in diagnosing epithelial components with cytological atypia and in differentiating various tumor types. One cytopathology diagnostic system is telecytology, which uses transmitted digital images and enables real-time diagnosis of EUS-FNA samples by expert cytologists at remote locations. However, EUS-FNA samples are useful for more than just diagnoses, as molecular analysis of these samples allows the identification of prognostic markers, such as genetic alterations in K-ras and EGFR. Expression of drug-metabolizing enzymes, human equilibrative nucleoside transporter 1, correlates with the response to gemcitabine-based chemotherapy. These pathology efforts have enhanced the diagnostic efficacy of EUS-FNA, thereby leading to better outcomes for patients with pancreatic diseases.

Acinar cell carcinoma of the pancreas presenting as diffuse pancreatic enlargement: Two case reports and literature review

RATIONALE

Pancreatic acinar cell carcinoma (ACC) is a rare malignant tumor of exocrine pancreas. It is typically a well-marginated large solid mass arising in a certain aspect of the pancreas. Diffuse involvement of ACC in the pancreas is very rare, and may simulate pancreatitis in radiological findings. We report 2 cases of ACC presenting as diffuse enlargement of the pancreas due to tumor involvement without formation of a distinct mass.

PATIENT CONCERNS

The patients consisted of a 41-year-old man with weight loss and a 77-year-old man who was asymptomatic.

DIAGNOSES

Computed tomography (CT) and 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT showed diffuse enlargement of the pancreas forming a sausage-like shape with homogenously increased FDG activity.

INTERVENTIONS

Endoscopic ultrasound (EUS)-guided fine needle aspiration (FNA) biopsy of the pancreatic lesion was performed.

OUTCOMES

Histopathology results from the pancreas confirmed the diagnosis of pancreatic ACC.

LESSONS

Because diffuse enlargement of the pancreas is a common imaging feature of pancreatitis, recognition of this rare morphologic pattern of ACC is important for radiological diagnosis of this tumor.

Pathology of Pancreatic Cancer Precursor Lesions

To better understand pancreatic ductal adenocarcinoma (PDAC) and improve its prognosis, it is essential to understand its origins. This article describes the pathology of the 3 well-established pancreatic cancer precursor lesions: pancreatic intraepithelial neoplasia, intraductal papillary mucinous neoplasm, and mucinous cystic neoplasm. Each of these precursor lesions has unique clinical findings, gross and microscopic features, and molecular aberrations. This article focuses on histopathologic diagnostic criteria and reporting guidelines. The genetics of these lesions are briefly discussed. Early detection and adequate treatment of pancreatic cancer precursor lesions has the potential to prevent pancreatic cancer and improve the prognosis of PDAC.

Nonductal Pancreatic Cancers

Nonductal pancreatic neoplasms, including solid pseudopapillary neoplasms, acinar cell carcinomas, and pancreatoblastomas, are uncommon. These entities share overlapping gross, microscopic, and immunohistochemical features, such as well-demarcated solid neoplasms, monotonous cellular tumor cells with little intervening stroma, and abnormal beta-catenin expression. Each tumor also has unique clinicopathologic characteristics with diverse clinical behavior. To differentiate nonductal pancreatic neoplasms, identification of histologic findings, such as pseudopapillae, acinar cell features, and squamoid corpuscles, is important. Immunostainings for acinar cell or neuroendocrine markers are helpful for differential diagnosis. This article describes the clinicopathologic and immunohistochemical features of nonductal pancreatic cancers.

Intraductal Tubulopapillary Neoplasm of the Pancreas: An Update From a Pathologist's Perspective

CONTEXT

-Intraductal tubulopapillary neoplasm (ITPN) is a rare intraductal epithelial neoplasm of the pancreas recently recognized as a distinct entity by the World Health Organization classification in 2010. It is defined as an intraductal, grossly visible, tubule-forming epithelial neoplasm with high-grade dysplasia and ductal differentiation without overt production of mucin. The diagnosis can be challenging owing to morphologic overlap with other intraductal lesions and its rarity. While recent advances in molecular genetic studies of ITPN have provided new tools to facilitate clinical diagnosis, the limited number of cases has yielded limited follow-up data to guide management.

OBJECTIVE

-To provide a clinical, pathologic, and molecular update on ITPN with respect to clinical presentation, imaging findings, histopathologic features, differential diagnosis, biological behavior, molecular characteristics, and treatment options.

DATA SOURCES

-Analysis of the pertinent literature (PubMed) and authors' research and clinical practice experience based on institutional and consultation materials.

CONCLUSIONS

-Clinical presentation, imaging findings, histopathology, immunohistochemistry studies, molecular characteristics, prognosis, and treatment options of ITPN are reviewed. Important differential diagnoses with other intraductal neoplasms of the pancreas-especially intraductal papillary mucinous neoplasm-using histopathologic, molecular, and immunohistochemical studies, are discussed. Despite the recent progress, more studies are necessary to assess the biology and genetics of ITPN for a better understanding of the prognostic factors and treatment options.

Undifferentiated Carcinoma With Osteoclastic Giant Cells of the Pancreas: Clinicopathologic Analysis of 38 Cases Highlights a More Protracted Clinical Course Than Currently Appreciated

Undifferentiated carcinomas with osteoclastic giant cells of the pancreas (OGC) are rare tumors. The current impression in the literature is that they are highly aggressive tumors similar in prognosis to ductal adenocarcinomas. In this study, the clinicopathologic characteristics of 38 resected OGCs were investigated and contrasted with 725 resected pancreatic ductal adenocarcinomas without osteoclastic cells (PDCs). The frequency among systematically reviewed pancreatic cancers was 1.4%. OGCs showed a slight female predominance (62.9%, vs. 51.4% in PDCs). The mean age was 57.9 years (vs. 65.0). The mean size of invasive cancer was 5.3 cm (vs. 3.2). They were characterized by nodular, pushing-border growth, and 8 arose in tumoral intraepithelial neoplasms (4 in mucinous cystic neoplasms, 4 in intraductal papillary mucinous neoplasms type lesions), and 23 (61%) also showed prominent intraductal/intracystic growth. Twenty-nine (76%) had an invasive ductal/tubular adenocarcinoma component. Osteoid was seen in 12. Despite their larger size, perineural invasion and nodal metastasis were uncommon (31.6% and 22.6%, vs. 85.5% and 64.0%, respectively). Immunohistochemistry performed on 24 cases revealed that osteoclastic cells expressed the histiocytic marker CD68, and background spindle cells and pleomorphic/giant carcinoma cells often showed p53 and often lacked cytokeratin. Survival of OGCs was significantly better than that of PDCs (5 yr, 59.1% vs. 15.7%, respectively, P=0.0009). In conclusion, pancreatic OGCs present with larger tumor size and in slightly younger patients than PDC, 21% arise in mucinous cystic neoplasms/intraductal papillary mucinous neoplasms, and 61% show intraductal/intracystic polypoid growth. OGCs have a significantly better prognosis than is currently believed in the literature.

Cytopathologic diagnosis of oncocytic type intraductal papillary mucinous neoplasm: Criteria and clinical implications of accurate diagnosis

BACKGROUND

Cytologic findings of pancreatic oncocytic-type intraductal papillary mucinous neoplasms (IPMNs)/intraductal oncocytic papillary neoplasms (IOPNs) are largely unknown.

METHODS

Five IOPNs encountered by the authors were analyzed.

RESULTS

Four IOPNs were located in the pancreatic head, and 1 was located in the pancreatic body/tail in 2 men and 3 women ages 56 to 84 years (mean age, 66 years). Radiologic diagnoses included pancreatic ductal adenocarcinoma (PDAC) in 2 patients, invasive cancer associated with IPMN in 1 patient, IPMN versus mucinous cystic neoplasm in 1 patient, and cystic mass in 1 patient. Cytologic findings included: hypercellular smears (4 of 5 cases) containing well formed clusters of oncocytic cells (5 of 5 cases) with prominent, slightly eccentric nucleoli (4 of 5 cases), predominantly arranged in sheets/papillary units (5 of 5 cases), with punched-out intercytoplasmic spaces (4 of 5 cases), and with occasional 3-dimensional groups and focal necrosis (3 of 5 cases). The intracytoplasmic mucin and thick extracellular mucin typical of other IPMNs were observed only in 2 cases and were very limited. The mean size on resection was 4.5 cm. Invasion was observed in 3 cases (0.1, 0.3, and 2.0 cm) of tubular-type IPMN. Initial cytologic evaluation was performed by the authors in 4 of 5 cases, which were diagnosed as IOPN (n = 3) and IPMN versus cystic PDAC (n = 1). One case was initially misdiagnosed as PDAC and, on resection, proved to be noninvasive IOPN.

CONCLUSIONS

Cytologic features of IOPNs are classical, similar to their histologic counterparts, and differ significantly from other IPMN subtypes. Because of their highly complex appearance, they are often radiologically misdiagnosed as PDAC; thus, failure to recognize their characteristic features on fine-needle aspiration may lead to inappropriate treatment. Patients with IOPN have an incomparably better prognosis than patients with ordinary PDAC, even when their neoplasms are invasive.

Difficult Diagnostic Problems in Pancreatobiliary Neoplasia

CONTEXT

Many common diagnostic dilemmas are encountered in pancreatobiliary pathology, frequently resulting in uncertainty on behalf of the pathologist and referral for a second opinion.

OBJECTIVES

To review 4 common diagnostic dilemmas encountered in the practice of pancreatobiliary pathology: (1) pancreatic ductal adenocarcinoma versus chronic pancreatitis; (2) pancreatic ductal carcinoma versus adenocarcinomas arising in the ampulla and intrapancreatic common bile duct; (3) the distinction of uncommon intraductal neoplasms--intraductal oncocytic papillary neoplasm, intraductal tubulopapillary neoplasm, and intraductal acinar cell carcinoma; and (4) intrahepatic cholangiocarcinoma versus metastatic carcinoma.

DATA SOURCES

A review of pertinent literature, along with the authors' personal experience, based on institutional and consultation materials.

CONCLUSIONS

Important diagnostic features for a few challenging problems in pancreatobiliary pathology are reviewed. Careful study of the microscopic features along with awareness of differential diagnoses and diagnostic pitfalls generally allows distinction of these entities. We also highlight established and novel ancillary studies that help to arrive at an accurate diagnosis.

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.

Intraductal dissemination of papillary adenocarcinoma of the ampulla of Vater in the pancreatic duct

It has been speculated that intraductal dissemination, via the pancreatic duct, bile duct, or mammary duct, is a unique form of cancer cell spread. However, clinical evidence to confirm this form of dissemination has been lacking. Here we report a case of papillary adenocarcinoma of the ampulla of Vater in which retrograde dissemination to the pancreatic duct was strongly suggested. A 79-year-old woman underwent pancreatoduodenectomy for a 22 mm microinvasive papillary adenocarcinoma of the ampulla. Multiple carcinomas in situ were found in the pancreatic duct distant from the ampulla. Seven months later, she underwent a second operation for a recurrent papillary adenocarcinoma at the pancreato-jejunal anastomosis showing exophytic and expansive growth into the jejunal lumen that connected to an intraductal adenocarcinoma in the pancreatic body. None of these tumors showed invasive growth, or vascular or neural invasion, being separate from each other but sharing identical histological, immunohistochemical, and molecular features; papillary growth, a pancreatobiliary phenotype, the same pattern of genomic loss of heterozygosity, and no mutation of the KRAS, TP53, and GNAS genes. These results imply that this papillary adenocarcinoma of the ampulla of Vater had disseminated to the pancreatic duct in a retrograde manner and recurred in the remnant pancreas.

Brush cytology of acinar cell carcinoma of the pancreas with intraductal growth: a case report

We describe a rare case of pancreatic acinar cell carcinoma (ACC) with intraductal growth in a 77-year-old man, which was diagnosed by endoscopic brush cytology. Preoperative imaging revealed an ill-defined mass involving the main pancreatic duct of the body, which was suspected to be an invasive ductal carcinoma. Endoscopic brush cytology showed several thick, small to large clusters of tumor cells. However, a loosely cohesive or individual cell arrangement was more prominent. Singly dispersed naked nuclei, occasionally with crush artifact, were frequently observed. The nuclear contour was smooth and chromatin was finely clumped. The cytoplasm contained many coarse D-PAS-positive granules. Histologically, the tumor expansively invaded to parenchyma and expanded to fill the pancreatic ducts. Ultrastructurally, the tumor cells were less cohesive with scarce tight junctions, and their cytoplasm contained numerous zymogen granules and filamentous inclusions. Although ACCs usually show expansive growth, the incidence of intraductal extension may be higher than previously considered. A few of the characteristic cytomorphological features described here may be useful for differential diagnosis of this tumor from malignant epithelioid neoplasms involving the large pancreatic ducts.

Clinicopathologic study of 62 acinar cell carcinomas of the pancreas: insights into the morphology and immunophenotype and search for prognostic markers

Acinar cell carcinoma (ACC) of the pancreas is a very rare tumor that has various morphologic features, which may give rise to diagnostic difficulties. Because of its rarity, many clinicopathologic characteristics remain to be further elucidated, and prognostic factors are yet to be well established. With the aim of better characterizing this carcinoma and searching for prognostic indicators, we collected 62 ACCs and investigated the following parameters: site, size, local infiltration, node and distant metastases, architectural pattern, nuclear atypia, presence of necrosis, lymphovascular and perineural invasion, proliferation, BCL10, trypsin, carboxyl ester lipase, amylase, lipase, PDX1, cytokeratin 19 (CK19), CK7, p53, and β-catenin expression. Twelve cases showing >30% of endocrine cells were reclassified as mixed acinar-neuroendocrine carcinomas, whereas 1 tumor was reclassified as a mixed ductal-acinar carcinoma and was excluded from the statistical prognostic evaluations. BCL10 and trypsin were the most reliable immunohistochemical markers, whereas amylase and lipase were not. Surgery was statistically correlated with a better prognosis (P=0.0008). Among resected tumors there was no difference in survival between ACCs and mixed acinar-neuroendocrine carcinomas, and factors that significantly correlated with poor prognosis were size >6.5 cm (P=0.004), lymph node (P=0.0039) and distant (P=0.008) metastases, and UICC stage (P=0.009). Stage was the only independent prognostic factor at multivariable analysis, and the best prognostic discrimination was observed on grouping together stages I and II and grouping together stages III and IV, suggesting a simplification of the UICC staging for such cancers. In addition, vascular and perineural invasion and CK19 and p53 expression showed a trend for poor prognosis, not reaching statistical significance.

Rare tumors in the pancreatic region

Pancreatic cancer is still considered to be one of the leading causes of cancer deaths. The most common of all the different types of pancreatic cancer is ductal original malignant tumors, and their clinical features are commonly characterized. However, for the rare tumors in the pancreatic region, the clinical features often vary, and detection of the cancers are detected late. Limited data are available to guide the management of very rare neoplasms of the pancreas. Therefore, to recognize or detect the rare tumors in the pancreatic region are of importance for the clinical practice.

Intraductal polypoid growth variant of pancreatic acinar cell carcinoma metastasizing to the intrahepatic bile duct 6 years after surgery: a case report and literature review

We present the first reported case of intraductal polypoid growth (IPG) variant of pancreatic acinar cell carcinoma (ACC) metastasizing to the intrahepatic bile duct. A 58-year-old Japanese woman had previously presented with obstructive jaundice and a 7.0 cm mass in the pancreatic head. She underwent biliary drainage for 2 months followed by pancreatectomy. Histological examination revealed a carcinoma with acinar pattern, immunohistochemically positive for trypsin, and acinar cell carcinoma was diagnosed. IPGs were prominent in the main pancreatic duct and its tributaries, extending into the intrapancreatic bile duct with tumor casts in the lumen. Imaging examinations 6 years later revealed a growing lesion within the intrahepatic bile duct. Needle biopsy examination suggested metastasis of ACC, and she underwent chemoradiation therapy and partial hepatectomy. Histological examination demonstrated ACC confined to the intrahepatic bile duct. The localization of metastasis and slow growth may indicate indolent biologic behavior of the IPG variant.

Exocrine Pancreatic Neoplasms of Nonductal Origin: Acinar Cell Carcinoma, Pancreatoblastoma, and Solid-Pseudopapillary Neoplasm

This review describes the clinicopathologic characteristics, differential diagnosis, and biologic behavior of exocrine pancreatic tumors of predominantly nonductal differentiation: acinar cell carcinoma, pancreatoblastoma, and solid-pseudopapillary neoplasm. Patients usually present with a well-demarcated, large, soft, solitary mass with expansile, rather than infiltrative, growth pattern. Cystic change is common. Histologically, the tumors usually reveal at least a focal solid, cellular appearance composed of uniform, monomorphic epithelial cells. However, each type has characteristic clinicopathological features. The immunohistochemical labeling profile of pancreatoblastoma parallels the multiple lines of differentiation. These tumors are capable of producing metastases; however, their behavior is different among the types and even in the same type. Therefore, establishment of a grading system that can predict the outcome would be helpful.