72 year-old male with no significant past medical history who presented with abdominal pain, loss of appetite and weight loss. Per imaging, the patient has liver, pancreas, peritoneal and lung lesions consistent with a metastatic disease. A peritoneal biopsy was performed. Slides are below.
Final Diagnosis: Pancreatic Acinar Cell Carcinoma
This is an acinar cell carcinoma of the pancreas with solid pattern of growth characterized by large sheets of cells without lumina that can also resemble the appearance of PanNETs. The most frequent patterns are acinar and solid, although a mixture is frequently found within an individual acinar cell carcinoma. In addition, uncommon subtypes including oncocytic, spindle, clear, and pleomorphic cell types have been described. Immunohistochemical stains for BCL10 and trypsin usually assist in their diagnosis since the sensitivity of combining both stains can reach up to 100%. Acinar cell carcinoma are usually CK7 positive. Beta-catenin is usually positive in 10% of cases and its usually not a diagnostic marker for pancreatoblatoma that can show areas of acinar cell differentiation. There is no specific genetic alteration that ties to acinar cell carcinoma but recent next generation sequence shows that these tumors can have SMAD4, CDKN2A, CDKN2B, ID3, ARID1A, among others.
In general, they are very rare tumors with an overall incidence of 1-2% of pancreatic tumors in adults. Most cases of acinar cell carcinoma present with vague abdominal pain (non-specific) and pancreatic mass. Jaundice is not a part of the usual clinical presentation. Patients with metastatic disease rarely show symptoms due to lipase hypersecretion, which include subcutaneous fat necrosis and polyarthralgia.