ACC is an uncommon solid epithelial exocrine tumour. There are very few reports on this type of tumour. ACC typically occurs during the fifth to seventh decades of life, with a male predilection [1
]. It can occur in any part of the pancreas, but the most common site is the head of the pancreas. A diagnosis of ACC can be made on the characteristic positive periodic acid–Schiff staining and immunohistochemical results.
The most common histological patterns seen in ACC are acinar and solid [2
]. In a study by Klimstra et al [3
], ACCs were positive for at least one immunohistochemical marker (i.e.
trypsin, lipase, amylase, chymotrypsin, α1-antitrypsin, keratin, epithelial membrane antigen, carcinoembryonic antigen and AFP). ACCs, unlike endocrine cell tumours, are believed to originate from transformed acinar cells [2
]. ACC with fatty change showed no evidence of an endocrine differentiation and diffuse immunoreactivity for AFP.
The imaging diagnosis of ACC varies owing to the rarity of the disease: a well-marginated, large, solid mass with a varied degree of cystic components; thin enhancing capsule; occasional central calcification; intralesional haemorrhage and less intense enhancement than a normal pancreas on both CT and MRI [4
]. ACC is unique among pancreatic tumours as it is characterised by increased AFP levels. Our case also showed increased AFP levels and less intense enhancement than the pancreas on both CT and MRI.
Although ACC shows increased blood AFP levels and positive AFP stain, AFP can also be expressed by hepatoid carcinomas. The pathogenesis of hepatoid carcinomas of the pancreas is not fully understood. Paner et al [6
] thought that the potentiality of hepatic differentiation may arise from any of the three main pancreatic cells (i.e.
acinar, ductal and islet cells). AFP can also be expressed by pancreatic ductal carcinoma, acinar cell carcinoma, islet cell tumour and poorly differentiated pancreatic adenocarcinoma [7
]. Therefore, the diagnosis of hepatoid carcinoma is mainly provided by the cancer's histological appearances on haematoxylin and eosin-stained material [8
In our case, fat-suppressed MRI confirmed that the pancreatic mass contained a fat component. The pancreas is a very rare location for fat-containing tumours [9
]. Differential diagnosis of fat-containing pancreatic tumours with direct invasion of pancreatic tissue should be mentioned (i.e.
malignant fibrous histiocytoma, leiomyosarcoma, desmoids tumour, cystic teratoma, fibrolipoma, liposarcoma and lipoblastoma) [10
]. However, as in our case, fat-containing tumours originating from the pancreas may be ACC with fatty change.
To our knowledge, this is the first reported case of ACC with fatty change. MRI is very important in detecting the fat component of tumours. ACC with fatty change must be considered in differential diagnosis of a fat-containing pancreatic tumour with elevated levels of AFP.