Pancreatic acinar cell carcinoma: A comprehensive review

Abstract

Acinar cell carcinoma (ACC) is a rare pancreatic malignancy with distinctive clinical, molecular, and morphological features. The long-term survival of ACC patients is substantially superior to that of pancreatic adenocarcinoma patients. As there are no significant patient series about ACCs, our understanding of this illness is mainly based on case reports and limited patient series. Surgical resection is the treatment of choice for patients with the disease restricted to one organ; however, with recent breakthroughs in precision medicine, medicines targeting the one-of-a-kind molecular profile of ACC are on the horizon. There are no standard treatment protocols available for people in which a total surgical resection to cure the condition is not possible. As a result of shared genetic alterations, ACCs are chemosensitive to agents with activity against pancreatic adenocarcinomas and colorectal carcinomas. The role of neoadjuvant or adjuvant chemoradiotherapy has not been established. This article aims to do a comprehensive literature study and present the most recent information on acinar cell cancer.

Keywords: Acinar cell carcinoma; Chemotherapy; Imaging; Immunohistochemical stains; Molecular features; Pancreas; Surgery.

Figure 1

Histopathological patterns. A: Acinar cell carcinoma with the predominant acinar pattern. The acinar pattern is characterized by structures resembling normal acini, with small lumina and cells arranged in a monolayer with basally located nuclei; B: Acinar cell carcinoma with the predominant glandular pattern. Acinar structures with dilated lumina characterize the glandular pattern; C: Acinar cell carcinoma with the predominant trabecular pattern. The trabecular pattern is characterized by ribbons of cells resembling those of pancreatic neuroendocrine tumors; D: Acinar cell carcinoma with a predominant solid pattern. Large sheets of cells characterize the solid pattern without lumina; E: Acinar cell carcinoma, immunohistochemical staining for trypsin; F: Acinar cell carcinoma, immunohistochemical staining for cytokeratin 7.

Figure 2

American Joint Committee on Cancer 8^th Edition cancer staging for exocrine pancreatic tumor such as pancreatic acinar cell carcinoma. A: Stage 0 (TNM: Tis, N0, M0). Tis = Carcinoma in situ. N0 = No regional lymph node metastases. M0 = No distant metastasis; B: Stage IA (TNM: T1, N0, M0). T1 = Tumor ≤ 2 cm in greatest dimension. N0 = No regional lymph node metastases. M0 = No distant metastasis; C: Stage IB (TNM: T2, N0, M0). T2 = Tumor > 2 cm and ≤ 4 cm in greatest dimension. N0 = No regional lymph node metastases. M0 = No distant metastasis; D: Stage IIA (TNM: T3, N0, M0). T3 = Tumor > 4 cm in greatest dimension. N0 = No regional lymph node metastases. M0 = No distant metastasis; E: Stage IIB (TNM: T 1/2/3, N1, M0). T 1/2/3 = Tumor ≤ 2 cm > 4 cm in greatest dimension. N1 = Metastasis in one to three regional lymph nodes. M0 = No distant metastasis; F: Stage III (TNM: T 1/2/3, N2, M0 or T4, Any N, M0). T 1/2/3 = Tumor ≤ 2 cm > 4 cm in greatest dimension. N2 = Metastasis in four or more regional lymph nodes. T4 = Tumor involves celiac axis, superior mesenteric artery, and common hepatic artery, regardless of size; G: Stage IV (TNM: Any T, Any N, M1). M1 = Distant metastasis. T = Primary tumor; N = Regional lymph node; M = Distant metastasis.

Figure 3

Stage IA (T1, N0, M0). A 77-year-old male patient with acinar cell carcinoma. Axial post-contrast portal-venous phase computed tomography image shows a solid mass (short arrows) measuring 1.8 cm × 1.6 cm and involving the region of the pancreatic head/body. Incidental findings are calcifications seen throughout the pancreas (likely related to changes in chronic pancreatitis) and mild dilatation of the biliary tree with pneumobilia (long arrow).

Figure 4

Stage IB (T2, N0, M0). An 89-year-old male patient with acinar cell carcinoma. Axial post-contrast computed tomography arterial phase image shows a large mass in the body of the pancreas (arrow) measuring 3.3 cm × 3 cm. No regional adenopathy is identified.

Figure 5

Stage IIA (T3, N0, M0). A 66-year-old patient with acinar cell carcinoma. Axial post-contrast computed tomography image in the arterial phase shows a solid lobulated mass measuring 6.5 cm × 5.4 cm arising from the tail of the pancreas (arrow). The mass is heterogeneous in density with areas of low-density and solid-enhancing areas. No regional or distant lymphadenopathy was detected.

Figure 6

Stage IIB (T3, N1, M0). A 61-year-old patient with acinar cell carcinoma. A: Axial post-contrast computed tomography (CT) image in the portovenous phase shows an infiltrative mass arising from the pancreatic body and tail (arrow); B: axial post-contrast CT images in the portovenous phase shows an enlarged mesenteric lymph node (arrow) measuring 2.6 cm × 1.2 cm; C: Axial positron emission tomography/CT image in the portovenous phase shows hypermetabolic pancreatic body and tail mass (arrow); D: Axial post-contrast CT images in the portovenous phase shows hypermetabolic enlarged mesenteric lymph node (arrow). Pathology of the mass revealed Acinar cell carcinoma with a metastatic mesenteric lymph node.

Figure 7

Stage IV. A 64-year-old patient with acinar cell carcinoma. A: Axial post-contrast image port venous phase shows a pancreatic head mass measuring about 3.2 cm × 2.8 cm (arrow); B: Axial post-contrast image port venous phase shows multiple bilobar variable-sized hepatic metastatic lesions (arrows). An incidental finding is an area of splenic infarction (asterisk in image A).