Comprehensive review of pancreatic acinar cell carcinoma: epidemiology, diagnosis, molecular features and treatment

Abstract

Pancreatic acinar cell carcinoma is a rare form (0.2-4.3%) of pancreatic neoplasm with unique clinical and molecular characteristics, which largely differ from pancreatic ductal adenocarcinoma. Pancreatic acinar cell carcinoma occurs more frequently in males and can occur in children. Serum lipase is elevated in 24-58% of patients with pancreatic acinar cell carcinoma. Pancreatic acinar cell carcinomas tend to be large at diagnosis (median tumour size: ~5 cm) and are frequently located in the pancreas head. Radiologically, pancreatic acinar cell carcinoma generally exhibits a solid appearance; however, necrosis, cystic changes and intratumoral haemorrhage can occur in larger lesions. Immunostaining is essential for the definitive diagnosis of pancreatic acinar cell carcinoma. Compared with pancreatic ductal adenocarcinoma, pancreatic acinar cell carcinoma has a more favourable prognosis. Although radical surgery is recommended for patients with pancreatic acinar cell carcinoma who do not have distant metastases, the recurrence rate is high. The effectiveness of adjuvant therapy for pancreatic acinar cell carcinoma is unclear. The response to FOLFIRINOX is generally favourable, and some patients achieve a complete response. Pancreatic acinar cell carcinoma has a different genomic profile compared with pancreatic ductal adenocarcinoma. Although genomic analyses have shown that pancreatic acinar cell carcinoma rarely has KRAS, TP53 and CDKN2A mutations, it has a higher prevalence of homologous recombination-related genes, including BRCA1/2 and ATM, than pancreatic ductal adenocarcinoma, suggesting high sensitivity to platinum-containing regimens and PARP inhibitors. Targeted therapies for genomic alternations are beneficial. Therefore, genetic testing is important for patients with pancreatic acinar cell carcinoma to choose the optimal therapeutic strategy.

Keywords: genomic analysis; homologous recombination deficiency; immune checkpoint inhibitor; immunostaining.

Figure 1

Case presentation of pancreatic acinar cell carcinoma (PACC). (A) Contrast-enhanced computed tomographic (CECT) image showing 6-cm heterogenous mass located in the pancreatic tail. (B) Endoscopic ultrasound image showing a hypoechoic mass with irregular contours, invading the gastric wall. (C) CECT image showing pancreatic tail tumour shrinkage 7 months after initiating modified FOLFIRINOX. (D–I) Pathologic findings of surgically resected PACC (distal pancreatectomy). (D) A surgically resected tumour localized in the body of the pancreas, formalin fixed, showing an expansive and partially encapsulated growth. (E) A lobular or confluent nodular cut-surface of tumour with an adjacent lymph-node metastasis (*). (F) A low-power microphotograph demonstrating hypercellular tumour in nests with scant fibrous stroma and necrosis (haematoxylin and eosin stain, ×20). (G) The acinar pattern characterized by small lumina and non-mucinous cells with stratified nuclei, occasionally with conspicuous nucleoli (haematoxylin and eosin stain, ×400). (H, I) Immunohistochemical positivity for trypsin (H) and Bcl-10 (I) (immunostaining, ×200).