Teaching Case

A 79-year-old male with a history of prostatic adenocarcinoma 8 years ago (T3bN0M1; surgically resected + RT + LHRH analogues for 36 months). Currently asymptomatic and free of disease. In a yearly follow-up, he is diagnosed with myotonic dystrophy type 2 and a slight elevation of PSA; a PET/CT (18F-choline) is ordered.

The PET/CT shows a heterogeneous mass of 29 x 39 mm in the body of the pancreas in contact with the splenic vein and with increased choline uptake (SUV max 16.4).

An MRI shows probable agenesis of the pancreatic tail (variant) and confirms a heterogeneous encapsulated mass with well-delimited margins in the pancreatic body. It has peripheral soft tissue protrusions with discrete contrast enhancement and some haemorrhagic foci. There is extension to the head and neck following the main pancreatic duct. The adjacent parenchyma has discrete signal alteration, and there is a mild oedematous infiltration of the peripancreatic fat. No biliary dilatation is observed. The splenic vein and artery are in contact, but without signs of invasion. Liver parenchyma and lymph nodes show no signs of extension.

The pancreatic acinar cell carcinoma (ACC) is a rare malignant pancreatic tumour arising from exocrine tissue (~1% of pancreatic tumours). It presents with vague symptomatology in elderly males >60 years [1]. The lipase hypersecretion syndrome (skin rashes, fat necrosis and polyarthralgias) is unique but rare (10% of cases). Diagnosis is made with a fine needle biopsy or at explant [2,3].

Radiologically, the ACC appears as a large mass with well-defined margins and a round or oval shape. It may be located anywhere in the pancreas [4]. Common elements include cystic/necrotic components and exophytic or multinodular growth [4]. The features with the highest characterisation potential are the presence of a capsule and the absence of bile duct dilation [5–7]. Calcifications or haemorrhages are rare [1]. On plain CT, it appears as a hypodense mass [8]. On MRI as hypo/iso intense on T1W, hyper/iso intense on T2W, and with restricted diffusion [5,9]. ACC is a slow-growing tumour lacking blood supply, and thus arterial enhancement is lower than that of pancreatic tissue but shows attenuation in portal phases [3,6]. A heterogeneous enhancement pattern is related to necrotic components [6,8]. Moreover, 10% of patients have pancreatic ductal ingrowth, which can also be observed in intraductal papillary mucinous and pancreatic neuroendocrine neoplasms. The ACC is locally invasive, usually associating lymph nodes or metastases [7].

Laboratory findings include pancreatic enzymes (trypsin, chymotrypsin) and a heterogeneous molecular profile (CK, β-catenin and KI-67) [1,6]. A subset of patients have BRCA2 mutations or somatic mutations of FAT family genes. BRCA2 mutations increase the risk for breast, pancreatic, prostatic and ovarian cancer. Surgery is the mainstay of therapy, with a possible role for radiotherapy, being BRCA2 patients the most benefited from chemotherapy [10,11]. ACC’s prognosis is sombre, despite being better than ADC, with tumour stage at diagnosis remaining the main prognostic factor.

In our case, a cephalic duodenopancreatectomy was performed. Histopathological analyses showed a heterogeneous tumour with soft centre, lobulated margins, partially encapsulated, with microscopic venous invasion and trypsin +. Extension studies showed heterozygosity for the pathogenic variant c.9026_9030 of BRCA2. The patient received the chemotherapy combination of capecitabine–oxaliplatin (CAPOX regimen), but there was hepatic M1 progression after 1 year.

The non-specific presentation along with a challenging histopathological diagnosis make imaging a cornerstone for ACC diagnosis [3]. Considering the genetic profile of the patient along with ACC’s association with other neoplasia may aid the radiologist to narrow down the differential diagnoses.

All patient data have been completely anonymised throughout the entire manuscript and related files.