Pancreatic Metastases and Lymphoma

Published on 19/07/2015 by admin

Filed under Radiology

Last modified 22/04/2025

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 Can be solitary (73%),  multiple (10%), or diffusely infiltrative (15%)

image Enhancement pattern mimics primary tumor

– Hypervascular: Most commonly renal cell cancer (RCC)
– Hypovascular: Lung, breast, colon, melanoma
image Concomitant intraabdominal metastases in > 60%, usually with widespread metastatic disease
• Pancreatic lymphoma

image Homogeneous soft tissue mass with little enhancement
image Diffuse enlargement of pancreas with infiltrating tumor (± peripancreatic fat involvement) may mimic acute pancreatitis
image Almost always associated lymphadenopathy or other sites of lymphomatous involvement
image Tumor classically encases peripancreatic vessels without narrowing or occlusion
image No dilatation of pancreatic duct or biliary tree

TOP DIFFERENTIAL DIAGNOSES

• Pancreatic ductal carcinoma

image Usually focal hypodense mass that obstructs main pancreatic duct resulting in upstream ductal dilatation
image Encases and narrows peripancreatic vessels
• Pancreatic islet cell tumors

image Usually hypervascular lesions which are indistinguishable from RCC metastases without clinical history

CLINICAL ISSUES

• Prognosis of metastases to pancreas poor, although isolated metastases to pancreas may be amenable to resection (especially RCC)

image RCC metastases to pancreas may occur 5-10 years after primary tumor resection
• Prognosis for primary pancreatic lymphoma is poor, with 30% cure rate after treatment
image
(Left) Axial CECT shows a hypodense mass image in the pancreatic tail due to metastatic sarcoma. Metastases from lung, breast, colon, or melanoma could have a similar appearance.

image
(Right) Coronal MIP reconstruction of an arterial phase CECT demonstrates an avidly enhancing pancreatic mass image in a patient with a history of prior nephrectomy for renal cell carcinoma (RCC), a characteristic appearance for an RCC metastasis. Based on appearance alone, this mass is indistinguishable from a neuroendocrine tumor.
image
(Left) Axial T1WI C+ MR shows an enhancing RCC metastasis image in the pancreatic head. The pancreatic duct image is mildly dilated upstream. Note the posterior position of the pancreatic tail as a result of a prior left nephrectomy for RCC several years prior to this scan.

image
(Right) Axial CECT shows diffuse infiltration of the pancreas and invasion of the spleen image by non-Hodgkin lymphoma. Also note the associated peripancreatic lymphadenopathy image.

IMAGING

General Features

• Best diagnostic clue

image Mass(es) in pancreas, usually without pancreatic or biliary ductal obstruction

CT Findings

• Pancreatic metastases

image May be solitary (73%), multiple (10%), or diffusely infiltrative (15%)
image Enhancement pattern is variable, but typically mimics primary tumor

– Hypervascular: Most often renal cell cancer (RCC)
– Hypovascular: Lung, breast, melanoma, colon
image Concomitant intraabdominal metastases in 60-95%, usually with widespread metastatic disease

– Liver, nodes, adrenal (each ∼ 30%)
image Dilatation of pancreatic duct or bile ducts less common than pancreatic adenocarcinoma (40%)
image Encasement or narrowing of peripancreatic vasculature is unusual
• Pancreatic lymphoma

image Most often presents as discrete homogeneous soft tissue mass with little enhancement
image May rarely present as diffuse enlargement of pancreas with infiltrating tumor ± peripancreatic fat involvement

– Infiltrating tumor may mimic acute pancreatitis
image Almost always associated with lymphadenopathy (especially peripancreatic) and other sites of lymphomatous involvement
image Tumor classically encases peripancreatic vasculature without narrowing or occlusion
image No dilatation of pancreatic duct or biliary tree
image No upstream atrophy of pancreatic parenchyma

MR Findings

• Pancreatic metastases

image RCC metastases typically demonstrate avid hypervascular enhancement (homogeneous when small and heterogeneous when large) on T1WI C+

– Usually low signal on T1WI and intermediate to high signal on T2WI
image Hypovascular metastases may demonstrate a rim of peripheral enhancement
• Pancreatic lymphoma

image Typically low signal on T1WI and low to intermediate signal on T2WI with little enhancement on T1WI C+

Imaging Recommendations

• Best imaging tool

image CECT ± PET/CT depending on primary tumor FDG avidity
• Protocol advice

image CECT: Inclusion of arterial phase critical if RCC metastasis is suspected

DIFFERENTIAL DIAGNOSIS

Pancreatic Ductal Carcinoma

• Usually a focal hypoenhancing mass with abrupt obstruction of pancreatic duct ± bile duct

image Diffuse infiltration of pancreas by tumor can very rarely occur, but much less commonly than lymphoma
• Commonly encases and narrows adjacent vessels (much more often than metastases or lymphoma)
• Bulky lymphadenopathy relatively uncommon

Pancreatic Islet Cell Tumors

• Hypervascular lesions which are indistinguishable from RCC metastases without clinical history

PATHOLOGY

General Features

• Etiology

image Pancreatic metastases

– Found incidentally at autopsy in 3-11% of oncology patients with widespread malignancy
– Most common primary sites: Renal (70%), breast (7%), lung (6%), colon (6%), melanoma (3%)
image Pancreatic lymphoma

– Primary lymphoma is very rare (< 1% of primary pancreatic tumors), and most often found in immunocompromised or elderly patients

image Usually B-cell non-Hodgkin lymphoma (NHL)
– Secondary lymphoma is much more common (30% of patients with widespread lymphoma)

CLINICAL ISSUES

Presentation

• Most often detected on CT or PET/CT performed for staging of known cancer
• Symptoms may result from involvement of pancreas, including jaundice, acute pancreatitis, or abdominal pain

Demographics

• Dependent on type of primary tumor or lymphoma sub-type

Natural History & Prognosis

• Pancreatic metastases

image Usually diagnosed at same time as primary tumor, but can present up to many years later
image RCC metastases to pancreas: May occur 5-10 years later
image RCC metastases are often isolated only to pancreas, and may be amenable to resection
• Prognosis

image Pancreatic metastases: Very poor in most cases (depends on type of primary tumor), although prognosis slightly better for RCC metastases isolated to pancreas
image Pancreatic lymphoma: Prognosis for secondary lymphomatous involvement dependent on lymphoma type

– Prognosis for primary pancreatic lymphoma is poor, with 30% cure rate after treatment

DIAGNOSTIC CHECKLIST

Consider

• Consider pancreatic metastasis with a pancreatic lesion in a patient with known primary malignancy
• Consider RCC metastases to pancreas even years after resection of primary tumor
• Consider lymphoma with an infiltrative hypoenhancing pancreas mass with bulky lymphadenopathy and no biliary/pancreatic ductal obstruction

Image Interpretation Pearls

• Overlapping radiographic features of pancreatic metastases, lymphoma, and primary carcinoma
image
(Left) Axial CECT shows bilateral necrotic adrenal metastases image from metastatic melanoma. Note also the associated pancreatic tail metastasis image.

image
(Right) Axial CT demonstrates a hypodense mass image with stippled calcification image involving the pancreatic head and neck. The stippled calcifications are not typical for pancreatic ductal adenocarcinoma and are more typical of this patient’s mucinous colon cancer, which has metastasized to the pancreas.
image
(Left) Axial CECT shows multiple solid, hypodense lesions image in the pancreas and kidneys image. This combination of findings is typical of renal and pancreatic involvement from non-Hodgkin lymphoma. A neck node biopsy confirmed the diagnosis.

image
(Right) Axial T1WI C+ MR demonstrates a subtle hypervascular lesion image in the pancreatic head. Note the absence of the right kidney, a finding that should suggest the correct diagnosis of a RCC metastasis.
image
(Left) Curved planar reformation from a CECT shows a normal pancreatic duct image. Note that the entire pancreatic body is displaced anteriorly by a large, hypodense, periaortic mass image that directly invades the body of the pancreas image.

image
(Right) Curved planar reformation of the celiac axis in the same patient demonstrates encasement image by hypodense nodal tissue. Biopsy of an axillary node revealed non-Hodgkin lymphoma.
image
(Left) Axial CECT demonstrates a markedly enlarged, hypodense, infiltrated pancreas image with surrounding induration and stranding. Superficially, this appearance could initially be suggestive of pancreatitis.

image
(Right) Axial CECT from the same patient demonstrates extensive lymphadenopathy image in the surrounding mesentery. Given this lymphadenopathy, the appearance of the pancreas represents diffuse lymphomatous infiltration of the pancreas in a patient with B-cell lymphoma.
image
(Left) Axial CECT shows a bulky exophytic mass image extending from the neck of the pancreas and exhibiting marked mass effect on the stomach image. The mass was found to be non-Hodgkin lymphoma after surgery.

image
(Right) Axial CECT shows a small hypodense mass image in the pancreatic body resulting in severe upstream pancreatic ductal dilatation image and parenchymal atrophy. While the imaging features are strongly suggestive of pancreatic cancer, this turned out to be a colon cancer metastasis.
image
(Left) Axial CECT shows absence of the kidney image in the left renal fossa and bulky hypervascular metastases image to the pancreas and liver image. While a neuroendocrine tumor could appear identical, the nephrectomy suggests the diagnosis of RCC metastases to the pancreas.

image
(Right) Axial arterial phase CECT shows avidly enhancing masses image in the pancreas and omentum image. The left kidney is absent in this patient with RCC mets, which are typically highly vascular, making the inclusion of arterial phase imaging very helpful for detection.
image
Axial CT in the arterial phase demonstrates an avidly enhancing pancreatic neck mass image in a patient whose left renal fossa surgical clips image indicate prior nephrectomy. This represents a characteristic appearance for metastatic renal cell carcinoma.

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