Discussion
Gastrointestinal lymphomas constitute 10-15% of all non-Hodgkin lymphomas and 30-40% of all extranodal lymphomas with Gastrointestinal non-Hodgkin lymphoma (NHL) usually involving the stomach and the small bowel. PPLs are rare. Most cases of pancreatic non-Hodgkin lymphoma usually present as a disseminated disease.[1] The most common histologic type of the pancreatic lymphoma is diffuse large B-cell lymphoma,[1] accounting for 77% to 80% of all patients.[3] PPL are also known to present as follicular lymphoma, small lymphocytic lymphoma, Burkitt’s lymphoma, and rarely as a T cell lymphoma. [3] The clinical presentation of primary pancreatic lymphoma is nonspecific, varying from abdominal pain which is most common presenting symptom , followed by abdominal mass , weight loss, jaundice , acute pancreatitis, small bowel obstruction and diarrhea .The classic symptoms of nodal non-Hodgkin’s lymphoma, such as fever, chills and night sweats are uncommon.[4]
Diagnostic criteria for PPL, as described by Dawson et al./ Behrns include (a) mass predominantly located in the pancreas with lymph nodes confined to the peri pancreatic region. (b) neither superficial lymphadenopathy nor enlargement of mediastinal lymph nodes on chest radiography (c) a normal leukocyte count in peripheral blood, and (d) no liver or splenic involvement. [4] These days however CT chest abdomen and/or PET-CT are standard baseline imaging tests, with higher sensitivity to pick up occult or small volume disease in the mediastinum and other sites, as illustrated in our case too.CA 19-9, Lactate dehydrogenase (LDH) and beta-2-microglobulin are essential serum markers for the diagnosis and differential diagnosis of PPL and for differentiating from pancreatic adenocarcinoma.[4] CA 19.9 tends to be raised in adenocarcinoma, while raised LDH would be more in favour of a lymphoma. Imaging studies tend to show a bulky localized tumor in the pancreatic head without significant dilatation of the main pancreatic duct, infrahilar retroperitoneal enlarged lymph nodes and invasive tumor growth not respecting anatomic boundaries with infiltration of surrounding structures. Also the presence of necrosis and calcification is unlikely in NHL. [5] However, the definitive diagnosis of PPL is based on the histopathological and cytopathological examinations. [3,5] For a definitive diagnosis, CT, or ultrasound-guided fine needle aspiration biopsy is the optimal approach, as it is highly accurate.[5]Pathological evidence is useful not only for the diagnosis, but also for the classification of lymphomas which is mandatory for the choice of chemotherapeutic regimen.[6]
Although morphologically different, these two lesions can still diagnosed using IHC which prove to be confirmatory in cases of ambiguity. In patients with aggressive lymphomas FDG-PET is done at baseline for staging, for interim evaluation and to assess response to therapy. It has shown to be a useful prognostic tool to predict relapse risk after the chemotherapy. Poorer clinical outcomes were seen in patients with positive FDG-PET scans as compared to patients with negative scans. [6]
Total pancreatectomy (Whipple procedure), which is standard of care for resectable pancreatic adenocarcinomas is considered to have no impact on survival in PPL and, because of associated morbidity, is not generally recommended for diagnosis and treatment of PPL.[4,7] Thus PPL are treated on similar lines to NHL at other sites. The poly-chemotherapy with R- CHOP represents the standard chemotherapy regimen for DLBL treatment with a complete response in 45-53% of cases and long-term survival of 30-37%.[6] The role of radiation therapy in PPL remains poorly defined. [8] Bouvet and colleagues have reported use of adjuvant radiation to decrease local failures.[9] Earlier Studies have shown some evidence that an initial surgical resection, when coupled with chemotherapy and radiotherapy, was associated with increased long-term survival of PPL[7], but R-CHOP remains standard for extranodal lymphomas. Prognosis of PPL is significantly better than pancreatic adenocarcinoma, with cure rates of up to 30% in earlier series compared to less than 5 % 5 year survivals for the latter.[10, 11, 12]