Primary pancreatic lymphoma: Masquerading as pancreatic abscess

Primary pancreatic lymphoma: Masquerading as pancreatic abscess

European Journal of Radiology Extra 59 (2006) 27–30 Primary pancreatic lymphoma: Masquerading as pancreatic abscess Sravan Kumar Marupaka a,∗ , Dinak...

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European Journal of Radiology Extra 59 (2006) 27–30

Primary pancreatic lymphoma: Masquerading as pancreatic abscess Sravan Kumar Marupaka a,∗ , Dinakar V.G. Unnithan a , Kamal C. Bhatt c , S.K. Singh b a

Department of Radiology, Sur Hospital, Ministry of Health, Sultanate of Oman Department of General Medicine, Sur Hospital, Ministry of Health, Sultanate of Oman c Department of General Surgery, Sur Hospital, Ministry of Health, Sultanate of Oman

b

Received 12 May 2005; received in revised form 23 April 2006; accepted 25 April 2006

Abstract Incidence of primary pancreatic lymphoma (PPL) among all pancreatic masses is about 0.5%. Necrosis and calcification are not known to occur in PPL though it may appear after the treatment with chemotherapy. Here we present a case of primary pancreatic diffuse large B-cell non-Hodgkin’s lymphoma (NHL) that showed evidence of necrosis and air on CT scan at the time of diagnosis mimicking pancreatic abscess. Available literature on PPL is also reviewed. © 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Primary pancreatic lymphoma (PPL); Pancreatic abscess; Computed tomography (CT); Diffuse large B-cell non-Hodgkin’s lymphoma; Extranodal lymphoma

1. Introduction Primary pancreatic lymphoma (PPL) constitutes less than 2% (0.16–4.9%) of the extra nodal non-Hodgkin’s lymphomas (NHL), whereas secondary involvement of pancreas in case of NHL is about 30%. Thirty to 40% of non-Hodgkin’s lymphoma is of extranodal variety. The most common extranodal site of origin is GIT comprising 50% of cases [1]. The B-cell variety of PPL is found worldwide and is more common than the T-cell type. The latter has been described only from Japan till date. Diffuse large B-cell NHL is the most common PPL, which makes up to 73% of all PPL. The 1-year actuarial survival rate in B-cell lymphomas is 51.9% and that in T-cell lymphomas is 0% [2]. Dawson’s criteria form the basis of diagnosing PPL. They include: (i) a mass centered in pancreas with involvement of peripancreatic nodes only, (ii) no superficial lymphadenopathy, (iii) no mediastinal lymphadenopathy on chest radiograph, (iv) no hepatic involvement, (v) no splenic involvement, (vi) normal leucocyte count in peripheral blood [3]. ∗ Correspondence to: Flat No. 2, Ahmed Al Jamy, Near Children’s Park, Shariya, PO Box No. 964, Sur, Postal code 411, Sultanate of Oman. Tel.: +968 2554 6720; fax: +968 2556 1558. E-mail address: [email protected] (S.K. Marupaka).

1571-4675/$ – see front matter © 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrex.2006.04.009

It is important to diagnose PPL because of its better prognosis in comparison with other pancreatic malignancies most common of them being pancreatic adenocarcinoma. By suspecting PPL on clinical and imaging grounds, surgery and its associated complications can be avoided, except perhaps as a bioptic procedure. An FNAC/core needle biopsy with flow cytometric and/or immunohistochemical studies is sufficient in most cases to make a definite diagnosis of PPL. Immunophenotyping of lymphomas to identify the cell lineage with the help of various monoclonal and polyclonal antibodies can be done even on routine paraffin embedded specimens. Phenotyping to differentiate between B-cell and T-cell lineage is important because T-cell phenotype is associated with poor prognosis [2].

2. Case report A 60-year-old gentleman presented with epigastric pain, anorexia and vomiting of 20 days duration. There was also history of undocumented weight loss. On examination he had epigastric mass. He was a known sickler. He had an unrelated history of fall from a camel 15 years ago with fracture femur.

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He was admitted to this hospital with a diagnosis of gastric outlet obstruction. At the time of admission he was in a poor general condition with moderately severe dehydration. He appeared pale but there was no jaundice. There were no enlarged lymph nodes. Abdominal examination revealed localized guarding in the upper abdomen. There was a vague fullness in the epigastrium which was tender on palpation. Liver and spleen were not palpable. Laboratory evaluation revealed normal total WBC count. Bilirubin, transaminases, alkaline phosphatase and amylase were within normal range. Carcinoembryonic antigen and Cancer antigen (CA)-25 were also normal. Erect chest radiograph did not show any free air under the domes of the diaphragm or mediastinal lymphadenopathy. Both lung fields and costophrenic angles were clear. Ultrasound examination revealed two separate masses in the region of pancreas. The larger mass was located in the region of tail of pancreas and the smaller one in the head. Bowel gas present in the region was thought to be responsible for obscuring the visibility of the masses but this was later found to be due to gas present in the lesion. There were no obvious peripancreatic, periportal or para aortic lymphadenopathy. Liver was normal in size and echo texture. No intraperitoneal free fluid was seen either in the Morrison’s pouch or in the Pouch of Douglas. CT scan was planned for further evaluation of the pancreatic mass. CT examination was performed on a TOSHIBA AUKLET, a single slice Spiral CT scanner. Twelve hundred milliliter of dilute barium (E-Z-Cat) was administered to opacify the bowel in 40 min and the last dose of 200 ml was given just before scanning with the patient on the table. Helical scan of the abdomen was performed with 5 mm slices covering the pancreas with a pitch of 1 and 10 mm slices covering the rest of the abdomen from the dome of diaphragm to the pubic symphysis with a pitch of 1.5. CT parameters were 120 kV, 150 mA and 512 matrix. Large FOV was selected (approximately equal to 35 cm). Hundred milliliter of Iohexol 300 mg/ml was injected by hand under pressure and scanning was started after 40 s. Reconstruction was done at 10 mm intervals throughout the abdomen and at 5 mm intervals in the region of pancreas. Multiplanar reconstructions were done and printed along with other images. There was leakage of oral contrast from the stomach (Fig. 1), which was later confirmed by UGI study with water soluble contrast. There was a large mass in the region of the tail and distal body of the pancreas measuring 25 cm × 20 cm in diameter with loss of surrounding fat planes. Stomach was displaced very much anteriorly by the mass. The central portion of the mass revealed irregular non-enhancing hypo dense areas interspersed with gas densities. Mild enhancement was seen in the rest of the mass. There was another smaller mass lesion without gas densities in the head of the pancreas. Pancreatic duct showed mild uniform dilatation (Fig. 2). The ratio of pancreatic duct diameter to the distal gland width was less than 0.5. Peripancreatic vasculature was not involved. No

Fig. 1. Primary pancreatic lymphoma. CECT shows large mass (double arrow) with central necrosis (white long arrow) and gas (small white arrow) possibly from gastric fistula. Leak (black arrow) of oral contrast from stomach secondary to perforation. STO indicates stomach.

obvious lymphadenopathy could be seen. There was no free intraperitoneal fluid. CT morphology of multiple rounded masses with irregular low density areas not enhancing after bolus contrast administration suggests necrosis within the mass. CT diagnosis of pancreatic abscesses was suggested. However, constitutional symptoms and leucocytosis were absent which was ascribed to patient’s old age. Gas within the lesion was thought to be due to a fistulous communication of the lesion with stomach. Patient was operated with a provisional diagnosis of multiple pancreatic abscesses with perforation of the stomach and gastric outlet obstruction. Any interventional procedure such as drainage of the abscesses or biopsy was not attempted because of the presence of gastric outlet obstruction and surgery was imminent.

Fig. 2. Primary pancreatic lymphoma. CECT shows multiple masses (double arrows) of different sizes in the pancreas. Note the central necrosis (white arrow). Pancreatic duct (black arrow) shows mild uniform dilatation. Peripancreatic vasculature not involved.

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On laparotomy there was a large growth from pancreas which was found adhered to the posterior wall of the stomach, the transverse mesocolon, upper pole of the left kidney and splenic flexure. It measured about 25 cm × 15 cm. Multiple enlarged lymph nodes were seen in the peripancreatic region. A nodule was seen on the serosal surface of the stomach. Liver was free of metastases. Spleen was compressed by the mass. No pelvic deposits were seen. Gastrojejunostomy was done as the mass was inoperable to relieve the gastric outlet obstruction. On gross examination during surgery a diagnosis of malignancy of pancreas with peripancreatic lymphnode secondaries with infiltration of the stomach was made. Biopsies were taken from all the representative areas and sent for histopathological examination. Histopathological examination revealed diffuse large Bcell non-Hodgkin’s lymphoma of the pancreas as per REAL (Revised European American Lymphoid) classification. On immunohistochemical studies it was positive for B-cell markers such as CD-20 and CD-79a and negative for T-cell markers. According to the updated Ann Arbor classification this was Stage IVA [4]. Nodule from serosa of stomach was found to be gastrointestinal stromal tumor (GIST) of low risk variety. Patient was referred to the oncology unit for further management.

3. Discussion In a nutshell, this patient presented clinically with an epigastric mass with gastric outlet obstruction. Cross sectional imaging revealed multiple ill-defined masses with non-enhancing necrotic areas interspersed with gas. At this juncture the lesions were thought to be pancreatic abscesses that were responsible for gastric outlet obstruction and perforation of the stomach, which led to laparotomy. Gross appearance on laparotomy suggested pancreatic malignancy. The histopathological diagnosis of diffuse large B-cell nonHodgkin’s Lymphoma was a surprise at the end. This case has demonstrated that histopathological examination is mandatory to establish the diagnosis of PPL. Clinical and radiological features are characteristic but not pathognomonic. A reliable method of diagnosing PPL is FNAC along with flow cytometry and immunohistochemical studies for immunophenotyping [4]. Retrospectively, the lesions were fulfilling the Dawson’s criteria for PPL [3]. The presence of necrosis favoured the diagnosis of pancreatic abscesses but ultimately proved to be PPL. In fact the presence of necrosis used to be a reliable finding to exclude PPL. To the best of our knowledge necrosis has not been reported in a case PPL in the reviewed literature [1,5,6]. We hereby report a case of primary pancreatic lymphoma, which mimics pancreatic abscesses and shows necrosis on CT scan. The present case demonstrates that PPL also should be one of the differential diagnoses for pancreatic masses even with necrosis.

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Contrast enhanced CT (CECT) is the best modality to evaluate pancreatic necrosis. Normal pancreas shows diffuse homogenous enhancement of the gland (homogenous pancreatogram). Necrosis is seen as areas of non-enhancement. CECT demonstrates 90% of severe necrosis and 79% of minor necrosis. Evaluation of necrosis by CECT is a superior indicator for surgery than other clinical grading methods of the severity of the necrosis. It is critical to detect infection of the necrosis as infected necrosis needs surgical evacuation. It is not possible to distinguish infected necrosis from non-infected necrosis on CT scans [7]. Absence of dilatation of common bile duct and intrahepatic biliary radicals, presence of only mild degree of uniform dilatation of pancreatic duct instead of significant irregular dilatation and the absence of encroachment of peripancreatic vasculature are the features that exclude pancreatic carcinoma [1] in this case. Incidence of pancreatic metastases was 3–10% in autopsy series. Out of which 17% were cases of multiple metastases. But pancreatic metastases usually are associated with concomitant metastases in other organs [8]. This patient does not have associated intraabdominal metastases other than peripancreatic lymph nodes detected on surgery. PPL has better prognosis and is usually amenable to chemotherapy or a combination of chemotherapy and radiotherapy. Therefore, surgical treatment is not necessary in majority of cases. The present case is one of the less common cases of PPL where surgery was required for the management of gastric outlet obstruction. Features of unresectability of PPL are large size (8 ± 2 cm), encroachment of mesenteric vessels and regional lymph node metastases [9]. Surgery has specific role in the context of PPL: (i) in cases where sufficient material for histopathological examination could not be obtained by non-surgical means, (ii) in cases of obstructive jaundice, for biliary by pass (currently there are many endoscopic and percutaneous stenting procedures available for biliary bypass), (iii) for resection of masses in stages I E and early II E [10], (iv) gastroenterostomy was performed in 25% of patients in one series [9]. Non-surgical bioptic methods available for evaluation of pancreatic masses are ultrasound or CT guided FNAC or core needle biopsy along with flow cytometric and/or immunohistochemical methods for immunophenotyping of the lymphoid masses. FNAC coupled with flow cytometric analysis appears to be highly accurate in the diagnosis of PPL [11]. A multicenter study done on FNAB in pancreatic masses concludes that it is efficacious and safe with a sensitivity of 87%, specificity of 100% and diagnostic accuracy of 91%. Studies of other bioptic procedures also showed similar results [12]. Endoscopic ultrasound is more sensitive than CT in detecting pancreatic masses and also more accurate than CT for local staging of pancreatic tumors. EUS is more useful in detecting early stage tumors where surgery is beneficial [13].

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Cases of PPL mimicking acute pancreatitis have been described by several authors in the past but without any evidence of necrosis [14,15]. The appearance of PPL on FDG PET is that of an intense round focus in the middle of the abdomen [16].

4. Conclusion We hereby report a case of a primary pancreatic lymphoma with a unique feature of central necrosis, which was not described in reviewed literature to the best of our knowledge.

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