Mixed acinar-endocrine carcinoma (MAEC) of the pancreas is a rare neoplasm, consisting of at least 25%–30% of acinar and neuroendocrine populations. Patients are often middle-aged and present with nonspecific symptoms. Imaging typically reveals a solid lesion in the pancreatic head. Management involves surgical resection and the overall prognosis is variable. Here, we present a case of a 48-year-old male who presented with a MAEC arising from duodenal pancreatic heterotopia. This is the one of the first cases, with histologic evidence, of MAEC arising from pancreatic heterotopia.
Pancreatic tumors are rare and may arise from either endocrine or exocrine components. Neuroendocrine cells make up the endocrine component, while ductal and acinar cells make up the exocrine component. The majority of pancreatic malignancies are ductal adenocarcinomas (>75%), followed by neuroendocrine tumors (NET) (7%), and acinar cell carcinomas (ACC) (1%) [
A 48-year-old male with past medical history of asthma, chronic pain, and obesity presented with progressive fatigue and epigastric discomfort for approximately six to eight weeks. A complete blood count revealed a hemoglobin level of 5.2 g/dL and esophagogastroduodenoscopy (EGD) demonstrated a large ulcerated mass in the duodenum, occupying approximately 90% of the circumference of the duodenal wall. The mass extended from the apex of the duodenal bulb to the major papilla; however, the major papilla was unremarkable. A follow up computed tomography scan showed a 6.0 × 5.5 × 5.0 cm hypoattenuating mass involving the mesenteric aspect of the second portion of the duodenum, which approached the proximal third segment of the duodenum. Additionally, the mass appeared to involve the pancreatic head and uncinate process; however, no hepatobiliary or pancreatic ductal obstruction was noted. Biopsy revealed a poorly differentiated carcinoma with neuroendocrine features. The patient underwent a pancreaticoduodenectomy (Whipple procedure) which showed a 10.2 × 8 × 2.7 cm pink-tan, lobulated, fungating mass with central necrosis within the duodenum. The mass was centered in the lumen of the duodenum with a well-demarcated (pushing) front of macroscopic invasion into the pancreas (Figure
Large fungating mass centered in the duodenum.
Microscopic examination of the lesion showed a neoplasm arranged primarily in lobules with prominent acinar formation. There were focal areas where the tumor was arranged in solid sheets. The neoplasm was located in the duodenum adjacent to an area of pancreatic heterotopia (Figures
(a and b) Duodenal tumor adjacent to pancreatic heterotopia composed of pancreatic acini, islets of Langerhans, and ducts (original magnification ×100 and ×200).
(a and b) Neuroendocrine cell component (original magnification ×100 and ×400).
(a and b) Acinar cell component (original magnification ×100 and ×400).
(a and b) Trypsin positivity in the acinar component (original magnification ×100 and ×200).
(a and b) Synaptophysin in the neuroendocrine component (original magnification ×100 and ×200).
(a and b) Chromogranin in the neuroendocrine component (original magnification ×100 and ×200).
Following surgical resection, the postoperative course was complicated by several bacterial infections, pulmonary abscesses, and liver metastases. Unfortunately, the patient died approximately six months after initial presentation.
MAEC is a rare pancreatic tumor, consisting of at least 25%–30% acinar and neuroendocrine cells [
Patients undergo initial evaluation with fine-needle aspiration, yet cytologic evaluation of MAEC can be extremely difficult. In some circumstances, it is easy to identify cells in an acinar formation that have granular cytoplasm and prominent nucleoli, suggesting ACC [
Definitive diagnosis of MAEC relies upon examination of the resection specimen to show the necessary proportion of acinar and neuroendocrine cells. There are two main patterns of MAEC described in the literature, which should be considered when the differential includes ACC, NET, and MAEC. These patterns include (1) two morphologically distinct and isolated populations of cells or (2) two intermingled populations of cells [
There are few reports of MAEC published in the literature, and even fewer published arising in pancreatic heterotopia. Moncur et al. [
The etiology and behavior of MAEC are not well understood. Literature documents fairly poor prognosis, similar to that of ACC, and suggests that tumors with increased numbers of neuroendocrine cells have a better prognosis [
The molecular characteristics of pancreatic NET, neuroendocrinecarcinoma (NEC), and ACC have been well characterized. Pancreatic NET and NEC have an average of 16 somatic mutations. The major genes involved in these somatic mutations are
Since the pathogenesis is not fully understood, there is no standardized treatment available for MAEC. With comparable aggressiveness to that of ACC [
In conclusion, we present a rare case of MAEC arising from pancreatic heterotopia in the duodenum. Owing to the morphologic overlap between MAEC, ACC, and NET, it is important to consider these differentials, especially when tissue is limited on FNA or cell block. ACC are much more aggressive than NET of the pancreas, and it is suspected that MAEC have a prognosis similar to that of ACC. Thus, it is important to accurately diagnose these lesions as the management may differ. With increased recognition of MAEC, especially with improved IHC, it is likely that additional studies will be completed which will contribute to improved management of these neoplasms.
The authors declare that they have no conflicts of interest.