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]