Primary pancreatic lymphoma with hepatic and renal involvement

A 54-year-old woman was admitted to our emergency department because of epigastric pain, and unexplained weight loss. Her medical history was unremarkable. Laboratory analysis revealed elevation of transaminases (alanine aminotransferase, 171 U/L [reference values 7-45 U/L]; aspartate aminotransferase, 250 U/L [reference values, 19- 25 U/L]), amylase (261 U/L [28-100 U/L]), lipase (598 U/L [13-60 U/L]), bilirubin (total 2.2 mg/dL [reference values; 1-1.3 mg/dL]; direct 2.1 mg/dL [01-0.3 mg/dL]).

Hepatic arterial (Fig.1) and portal venous (Fig.2) phase contrast-enhanced CT images showed diffuse enlargement and poor enhancement of the pancreas (*) with dilatation of intrahepatic bile ducts. Multiple small hypoattenuating hepatic (white arrows) and renal (black arrows) nodules were also noted.

A diagnosis of autoimmune pancreatitis or primary pancreatic lymphoma with hepatic and renal involvement was considered.

On subsequent MRI, the pancreas showed hypointensity on both unenhanced T1- and T2-weighted images (Fig.3-4), strong hyperintensity on high-b-value diffusion-weighted images suggesting restricted diffusion (Fig.5) and slight enhancement on contrast-enhanced hepatic arterial (Fig.6) and portal-venous (Fig.7) phase images. Hepatic and renal nodules showed hypointensity on unenhanced T1-weighted images, hyperintensity on T2-weighted images, strong hyperintensity on high-b-value diffusion-weighted images and slight enhancement on contrast-enhanced images.

The diagnosis of primary pancreatic Burkitt’s lymphoma was established by means of percutaneous ultrasonographically guided biopsy.

Primary pancreatic lymphoma (PPL) is an unusual (< 2% of cases) extra-nodal manifestation of B-cell non-Hodgkin’s lymphoma, out of which Burkitt’s lymphoma is extremely rare [1]. Diagnosis of PPL is done when the bulk of the disease is localized to the pancreas even if contiguous nodal involvement or distant spread can be found [1,2].

There are two forms of PPL: focal and diffuse [1,2]. The latter was observed in our case.

The diagnosis of PPL is challenging since a diffuse enlargement of the pancreas can be due to several diseases such as acute pancreatitis, autoimmune pancreatitis, diffuse infiltrative pancreatic carcinoma and multiple pancreatic metastases [3-6].

Moreover, characteristic presentation of lymphoma (e.g., fever, chills, and night sweats) is extremely rare (2% of cases) in patients with PPL [7]. Indeed, the patient presented with epigastric pain, weight loss, and obstructive jaundice. 

Our case showed diffuse enlargement of the pancreas with poor definition of the contours, hypoattenuation at CT, hypointensity on both T1- and T2-weighted MR images, and slight contrast enhancement.

Given hepatic and renal involvement, a diagnosis of autoimmune pancreatitis was also considered.

Autoimmune pancreatitis is a systemic disease characterized by abun­dant pancreatic infiltration of IgG4-positive plasma cells and fibrosis with extensive extra-pancreatic involvement [4].

Although typical findings of autoimmune pancreatitis include a diffusely enlarged sausage-like pan­creas with low enhancement on contrast-enhanced CT and MR images, mild hyperintensity on T2-weighted images and a characteristic capsule-like rim or “halo” due fluid, phlegmon, help differentiate autoimmune pancreatitis from PPL [5].

T2-hypointensity also helps exclude diffuse pancreatic adenocarcinoma and metastases [3].

Acute pancreatitis may also mimic PPL. However, the characteristic clinical-laboratory findings (e.g., serum amylase or lipase level greater than three times the upper normal value), peripancreatic inflammation, necrotic and fluid collections allow a correct diagnosis of acute pancreatitis [6].

Our case shows slight and homoge­neous contrast enhancement of the pancreas except for small foci of reduced or absent enhancement. This feature helps exclude pancreatic metastases and adenocarcinoma that typically show ring-like and heterogeneous contrast-enhancement, respectively [3].

Typically, PPL shows strong and homogeneous hyperintensity on high-b-value diffusion-weighted images (i.e., similar to that of the spleen) with hypointensity on corresponding ADP map suggesting restricted diffusion [2]. Meanwhile, acute pancreatitis and autoimmune pancreatitis can show a similar appearance [3,5]. Diffuse pancreatic adenocarcinoma and metastases show a heterogeneous hyperintensity on high b-value diffusion-weighted images [3].

Bile duct dilatation is a rarely observed in PPL and more likely suggests pancreatic adenocarcinoma [3]. However, diffuse pancreatic adenocarcinoma shows a characteristic heterogeneous appearance and irregular pancreatic contours, features not observed in our case [3]. Bile duct dilation can also be due to autoimmune pancreatitis [5].

Treatment and prognosis of PPL are different from those of other causes of diffuse pancreatic enlargement. Thus, biopsy is usually recommended to establish the diagnosis.

The standard of care for PPL is chemotherapy or radiotherapy, which leads to a high complete response rate and long-term survival [7].

Teaching points

Primary pancreatic lymphoma should be considered in the differential diagnosis of diffuse enlargement of the pancreas.

Primary pancreatic lymphoma has an unusual clinical presentation.