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Lymphomas do not only arise in lymph nodes. Whilst Lymphomas generally start in lymph nodes they may also occur in collections of lymphatic tissue in organs like the stomach or intestines or rarely the pancreas. Many arise in these non-lymphoid (also known as extra-lymphatic or extra-nodal) sites such as the skin and gastrointestinal tract. Lymphoma of the pancreas is uncommon. Secondary invasion from contiguous, retroperitoneal lymph node disease is the predominant mode of involvement. Lymphoma originating in and remaining localized to the pancreas is very rare.
Lymphoma includes Hodgkin’s and non-Hodgkin’s forms. Hodgkin’s lymphomas rarely disseminate to extralymphatic organs, while non-Hodgkin’s lymphomas often invade extra-lymphatic organs. Most primary pancreatic lymphomas (PPL) are non-Hodgkin’s Lymphomas. 30-40% of non-Hodgkin’s lymphomas originate from extra-lymphatic organs, about 30 percent of which may involve the pancreas.
Isolated primary pancreatic lymphoma (PPL) is a rare extra-lymphatic non-Hodgkin's lymphoma comprising less than 1% of all extra-lymphatic lymphomas.
As with adenocarcinoma incidence increases with age. There is a slight male preponderance. It is difficult to diagnose; the vague presenting symptoms and nonspecific laboratory/radiological findings make it difficult to differentiate the condition from pancreatic adenocarcinoma. Histopathological examination is of paramount importance to conclusively establish the diagnosis since the treatment involves lymphoma protocols (not standard adenocarcinoma pancreatic cancer protocols and may be done by the haematological cancer rather than Upper GI cancer team), and prognosis and survival in PPL are considerably superior to that in adenocarcinoma pancreas.
The majority of the patients present with vague abdominal complaints such as dyspepsia, nausea, flatulence, abdominal cramps, jaundice, reflux, weight loss, bowel obstruction, palpable abdominal mass, and even diarrhea. Sometimes the clinical presentation mimics acute pancreatitis. Obstructive jaundice is less common than in pancreatic cancer. Lymphoma B-symptoms are uncommon at presentation.
Patients are sometimes not found to have Non-Hodgkin's Lymphoma until after primary surgical excision or partial pancreatectomy or even Whipple's procedure performed on exploratory laparotomy. However, if diagnosed preoperatively (eg by EUS - endoscopic ultrasound), the treatment strategy involves chemotherapy (eg R-CHOP) and radiotherapy along the lines of non-Hodgkin's lymphoma, with surgical intervention being reserved for those cases requiring biliary or gastric bypass to relieve the symptoms. Local radiotherapy up to a total of 40 Gy has been used as consolidation after chemotherapy. Cure rates of up to 30% are reported for patients with PPL.
A CT scan is commonly used for the detection of pancreatic lymphoma. Two types of morphological presentation have been reported on CT; one is a tumor-like, localized, well-circumscribed mass presenting as a hypoechogenic mass (structures poorly rebounding the ultrasound waves), and the second is a diffuse enlargement infiltrating the pancreas. The well-circumscribed tumoral form is distinguished from pancreatic adenocarcinoma by the absence of pancreatic duct involvement and the presence of surrounding lymphadenopathy. The imaging findings in the second type are similar to those in acute pancreatitis.
The majority of patients with pancreatic cancer, whether it is adenocarcinoma or lymphoma, present with a mass in the head of the gland. Pancreatic lymphoma is often described as a large homogeneous mass with extra-pancreatic extension, with or without associated lymphadenopathy. Less common presentations are masses in the body or tail, or more rarely diffuse involvement of the pancreas. Abdominal Non Hodgkins Lymphoma typically present themselves as a solid mass and they cause abdominal pain due to compression or infiltration of nerves and its pain is often referred as a diffuse pain.
An exceedingly rare entity, isolated PPLs need to be differentiated from pancreatic adenocarcinomas by histopathological evaluation since management is on the lines of other extralymphatic lymphomas and prognosis is significantly better.
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