Pancreatic lymphoma is a rare hematological malignancy involving the pancreas. Primary pancreatic lymphoma constitutes less than 1% of all pancreatic malignancies, while secondary involvement (spread of nodal or extranodal lymphoma to the pancreas) is much more common. Non-Hodgkin lymphoma (especially diffuse large B-cell lymphoma — DLBCL) is the most common subtype. It characteristically presents as a large, homogeneous, hypoattenuating/hypointense mass and can encase vessels without invasion despite its size. This feature is the most important clue in differentiation from adenocarcinoma. The pancreatic duct does not show significant dilatation and upstream parenchymal atrophy is not expected.
Age Range
50-70
Peak Age
60
Gender
Male predominant
Prevalence
Rare
Pancreatic lymphoma results from monoclonal proliferation of lymphoid cells in the pancreatic parenchyma. In the primary form, lymphoma arises from peripancreatic lymph nodes or rare intrapancreatic lymphoid tissue. In the secondary form, the pancreas is involved through hematogenous or lymphatic spread of systemic lymphoma. Lymphomatous tissue creates dense, homogeneous cellular infiltration — this homogeneity is reflected on imaging as markedly homogeneous hypoattenuation. Unlike adenocarcinoma, lymphoma tissue does not create intense desmoplastic reaction; instead, it can elastically contact the vessel wall, encasing vessels without invasion. This 'vessel encasement without invasion' phenomenon results from the low capacity of lymphomatous cells to penetrate vascular walls. The pancreatic duct can similarly be compressed but complete obstruction is rare and significant upstream dilatation does not occur — this is an important distinction from adenocarcinoma.
A large pancreatic mass completely or partially encases peripancreatic vascular structures (SMA, SMV, portal vein, splenic vein) but the vessel lumen remains patent with normal caliber, vessel wall is smooth-contoured, and no tumor thrombus is present. This pattern is considered pathognomonic for lymphoma and constitutes the fundamental difference from the invasive vascular involvement of adenocarcinoma. The low mesenchymal invasion capacity of lymphoid cells forms the basis of this phenomenon.
On arterial phase, a large, markedly homogeneous hypoattenuating mass is seen. It enhances much less than pancreatic parenchyma. The mass is typically >5 cm and homogeneity is preserved regardless of size (necrosis rare). Mass borders are usually smooth or lobulated.
Report Sentence
A large, homogeneous, markedly hypoattenuating mass is seen in the pancreas, consistent with pancreatic lymphoma.
On portal venous phase, peripancreatic vascular structures (SMA, SMV, portal vein, splenic vessels) are encased by the mass but remain patent with normal caliber. No luminal narrowing or occlusion. Vessel wall is smooth and no tumor thrombus is seen.
Report Sentence
Peripancreatic vascular structures are encased by the mass but remain patent with normal caliber and no vascular invasion is identified; this finding is strong evidence favoring lymphoma.
On portal venous phase, despite the large mass, the main pancreatic duct does not show significant dilatation. The CBD may be mildly affected but 'double duct sign' is not expected. No atrophy in the upstream pancreatic parenchyma.
Report Sentence
Despite the large pancreatic mass, the main pancreatic duct does not show significant dilatation, and this finding favors lymphoma.
On T2-weighted sequences, the mass appears homogeneous, mildly to moderately hyperintense. Significant heterogeneity or necrosis is not expected. Shows mildly higher signal than normal pancreatic parenchyma.
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The mass appears homogeneous and mildly to moderately hyperintense on T2-weighted sequences, showing a solid homogeneous mass appearance consistent with lymphoma.
On DWI, the mass shows marked diffusion restriction — bright signal at high b-values and low ADC values on ADC mapping. The high cellularity of lymphoma causes this marked restriction.
Report Sentence
The mass demonstrates marked diffusion restriction on DWI consistent with high cellularity, strongly supporting lymphoma diagnosis.
On portal venous phase, enlarged lymph nodes may be seen in retroperitoneal and/or mesenteric regions. LAP is homogeneously hypoattenuating consistent with lymphomatous involvement. Bilateral renal hilar, para-aortic, and aortocaval LAP are common locations.
Report Sentence
Multiple enlarged lymph nodes are seen in the retroperitoneal and mesenteric regions, supporting lymphoma diagnosis together with the pancreatic mass.
Criteria
Main lymphoma mass localized in the pancreas, no or minimal peripheral LAP, no bone marrow involvement, no liver/spleen involvement, normal white blood cell count
Distinct Features
Very rare (<1% of pancreatic malignancies). Usually a large, solitary mass in the pancreatic head. DLBCL is the most common histological subtype. Response rate to chemotherapy is high (80%+). Surgery is generally not required — chemotherapy is administered after diagnosis by biopsy.
Criteria
Pancreatic involvement in the setting of known systemic lymphoma, multiple organ involvement accompanies, widespread LAP
Distinct Features
Much more common than primary form. Spleen, liver, kidney involvement may accompany. Widespread retroperitoneal and mesenteric LAP is seen. Pancreatic involvement can be focal mass or diffuse infiltration. Treatment depends on the systemic lymphoma regimen.
Criteria
Diffuse infiltration of the pancreas by lymphomatous tissue, diffuse enlargement instead of focal mass, may mimic AIP
Distinct Features
Pancreas is diffusely enlarged and homogeneously hypoattenuating — may resemble the sausage-shaped pancreas of AIP. However, capsule-like rim is absent, IgG4 elevation is not expected, and steroid response is temporary. Diffusion restriction on DWI may be more intense than AIP.
Distinguishing Feature
Adenocarcinoma shows vascular invasion (vessel wall infiltration, luminal narrowing, occlusion), significant upstream duct dilatation, parenchymal atrophy, and heterogeneous enhancement. In lymphoma, vessel encasement without invasion, absence of duct dilatation, homogeneous hypoattenuation, and accompanying LAP are distinguishing.
Distinguishing Feature
In AIP, capsule-like rim, delayed enhancement, IgG4 elevation, and steroid response are expected. In lymphoma, capsule-like rim is absent, enhancement remains minimal, diffusion restriction on DWI is more marked (ADC <0.8 vs 0.9-1.2 in AIP), and LAP accompanies.
Distinguishing Feature
NET shows intense homogeneous arterial enhancement (hypervascular). Lymphoma remains hypoattenuating in all phases. NET is usually a smaller, well-defined mass without accompanying LAP. Hormonal symptoms may be present in functional NETs.
Distinguishing Feature
Metastasis is usually multifocal, has a known primary malignancy history, and lesion enhancement pattern varies by primary tumor (hypervascular: RCC, melanoma; hypovascular: lung, colon). Lymphoma is usually a solitary large homogeneous mass showing vessel encasement without invasion.
Urgency
urgentManagement
medicalBiopsy
NeededFollow-up
3-monthPancreatic lymphoma diagnosis requires histological confirmation — tissue should be obtained by EUS-FNA or core biopsy. Flow cytometry and immunohistochemistry are mandatory for subtype determination. Treatment is chemotherapy and/or radiotherapy, not surgery — therefore differentiation from adenocarcinoma is critically important (Whipple procedure should not be performed unnecessarily). R-CHOP (rituximab + cyclophosphamide + doxorubicin + vincristine + prednisolone) is the standard regimen for DLBCL. Response rate is 80%+ and prognosis is much better than adenocarcinoma. PET-CT is used for staging and treatment response assessment. Post-treatment follow-up should be performed with CT/MRI every 3 months and PET-CT every 6 months.
Pancreatic lymphoma responds well to chemotherapy and surgery is generally not indicated. Therefore, differentiation from PDAC is critical for treatment planning. Histopathological diagnosis via biopsy is required.