Acinar cell carcinoma (ACC) is a rare malignant neoplasm comprising 1-2% of pancreatic exocrine tumors. It originates from pancreatic acinar cells and may secrete pancreatic enzymes such as lipase and trypsin. It typically presents as a large (>5 cm), well-defined, exophytic mass. It may have a mixed solid-cystic architecture. Unlike ductal adenocarcinoma, it has a better prognosis (5-year survival 25-45%). Lipase hypersecretion syndrome (subcutaneous fat necrosis, polyarthralgia, eosinophilia) occurs in 10-15% of patients and is clinically pathognomonic. More common in males, median age 55-60.
Age Range
50-80
Peak Age
65
Gender
Male predominant
Prevalence
Rare
ACC originates from pancreatic acinar cells — these cells normally synthesize pancreatic enzymes (lipase, amylase, trypsin, elastase). The tumor may continue functional enzyme secretion — particularly lipase hypersecretion leads to systemic effects: excessive circulating lipase breaks down subcutaneous and periarticular fat tissue, creating subcutaneous fat necrosis nodules and polyarthralgia. This clinical triad (subcutaneous nodules + arthralgia + eosinophilia) is known as 'lipase hypersecretion syndrome' and is pathognomonic for ACC. Regarding imaging, ACC's large size reflects the tumor's slow growth rate — unlike ductal adenocarcinoma, it does not cause early vascular invasion or ductal obstruction. Its well-defined encapsulated structure (pseudocapsule) results from the exophytic growth pattern. The mixed solid-cystic architecture reflects the tumor's necrotic and hemorrhagic degeneration — solid components represent active tumor, cystic areas represent necrosis/hemorrhage.
A large (>5 cm), well-defined, exophytic, mixed solid-cystic pancreatic mass combined with lipase hypersecretion syndrome (subcutaneous fat necrosis, polyarthralgia, eosinophilia) is a pathognomonic combination for ACC. The clinical syndrome occurs in 10-15% of patients, but when present, the diagnosis is virtually certain.
In the arterial phase, ACC shows heterogeneous enhancement — prominent enhancement in peripheral solid components, no enhancement in central necrotic/cystic areas. Enhancement pattern may vary from hypodense to hypervascular. In large tumors, prominent peripheral enhancement with central necrosis ('rim enhancement') may be observed.
Report Sentence
Peripheral enhancement with central necrosis is observed in the large pancreatic mass in the arterial phase, and acinar cell carcinoma should be considered in the differential.
On non-contrast CT, ACC appears as a large (usually >5 cm), well-defined mass with heterogeneous attenuation. Low-attenuation areas represent necrosis and cystic degeneration. Calcification is rare (10-15%). Exophytic growth pattern is typical — the mass extends beyond the pancreatic contour.
Report Sentence
A large, well-defined, exophytic mass with heterogeneous attenuation and internal necrotic/cystic areas is identified in the pancreas.
On T1-weighted MRI, ACC is typically heterogeneously hypointense. Hemorrhagic areas show focal T1 hyperintensity — this finding is relatively common in ACC. On fat-suppressed T1, the hemorrhagic component becomes more conspicuous.
Report Sentence
Heterogeneously hypointense signal is observed in the mass on T1-weighted sequences with focal hyperintense areas consistent with internal hemorrhage.
On T2-weighted MRI, ACC shows heterogeneous signal — cystic/necrotic areas are markedly hyperintense, solid areas are intermediate-to-hyperintense. The capsule may be seen as a hypointense ring on T2. T2 imaging best evaluates the proportion of cystic and solid components.
Report Sentence
Heterogeneous signal is observed in the mass on T2-weighted sequences with markedly hyperintense cystic/necrotic components and intermediate signal solid areas.
On DWI, diffusion restriction is observed in solid components — reflecting high cellularity. ADC values are low, supporting malignancy. No diffusion restriction in cystic and necrotic areas. DWI is useful for evaluating solid component proportion and treatment response.
Report Sentence
Diffusion restriction limited to solid components is observed in the mass on DWI, consistent with malignancy.
On ultrasonography, ACC appears as a large mass with heterogeneous echogenicity. Solid components are hypoechoic-isoechoic, cystic/necrotic areas are anechoic. A well-defined capsular structure may be visible. Increased vascularity in solid components may be seen on Doppler.
Report Sentence
A large mass with heterogeneous echogenicity and mixed solid-cystic architecture is identified in the pancreas, and further imaging is recommended.
Criteria
>95% acinar differentiation, enzyme secretion present, trypsin/lipase positive
Distinct Features
Most common type. Lipase hypersecretion syndrome occurs in this type. Immunohistochemistry positive for trypsin, lipase, BCL10, chymotrypsin. CK19 negative (differentiation from ductal adenocarcinoma).
Criteria
Acinar + neuroendocrine component (each >30%), additionally positive for synaptophysin/chromogranin
Distinct Features
Rare. Imaging findings similar to pure ACC. Hypervascular component in arterial phase may reflect neuroendocrine component. Prognosis similar to pure ACC.
Criteria
Predominantly cystic architecture, lined by acinar epithelium, can be very large (>10 cm)
Distinct Features
Very rare variant. Cystic component predominant — may be confused with serous cystadenoma or MCN. Acinar enzyme markers positive. Prognosis may be better than solid form. Surgical resection is curative.
Distinguishing Feature
Ductal adenocarcinoma is hypovascular (hypodense in arterial phase), ill-defined, characterized by prominent desmoplastic reaction, ductal obstruction, and upstream atrophy. ACC is well-defined, exophytic, mixed solid-cystic, and ductal obstruction is usually absent. Ductal adenocarcinoma is T2 hypointense (fibrous stroma), ACC is T2 intermediate-to-hyperintense.
Distinguishing Feature
Large non-functional pNETs may resemble ACC. pNET shows more homogeneous hypervascular arterial enhancement. Lipase hypersecretion syndrome seen in ACC does not occur in pNET. On immunohistochemistry, chromogranin A/synaptophysin is positive in pNET, trypsin/lipase is positive in ACC.
Distinguishing Feature
SPN typically occurs in young women (20-30 years) — ACC in middle-aged to elderly men (55-60). Both are large, mixed solid-cystic, and encapsulated. SPN has peripheral calcification, calcification is rare in ACC. In SPN, AFP and enzyme levels are normal; in ACC, lipase may be elevated.
Distinguishing Feature
Pancreatoblastoma occurs in childhood (1-8 years) — ACC in adults. Calcification is much more frequent in pancreatoblastoma (30-70% vs 10-15%), AFP is elevated. Lipase hypersecretion syndrome in ACC and AFP elevation in pancreatoblastoma are diagnostic clues.
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
specialist-referralSurgical resection is the primary approach for ACC treatment. Unlike ductal adenocarcinoma, ACC is usually diagnosed in a resectable state — well-defined structure and late vascular invasion increase the chance of resection. R0 resection achieves 5-year survival of 25-45%, significantly better than ductal adenocarcinoma (<10% 5-year). Liver metastases are the most common distant spread site. When lipase hypersecretion syndrome is present, the syndrome usually regresses after surgery. Chemotherapy (FOLFIRINOX, gemcitabine-based) is used in unresectable or metastatic cases. Biopsy is needed for histological typing and differentiation from ductal adenocarcinoma.
Acinar cell carcinoma has a better prognosis than PDAC. Surgical resection is the primary treatment. Lipase hypersecretion syndrome may be a diagnostic clue. Even with liver metastasis, longer survival is expected due to slower growth.