Giardia-filled Pancreatic Mass in a Patient With Recently Treated T-cell-rich B-cell Lymphoma

Giardia lamblia (G. lamblia)-filled pancreatic masses are a rarely reported entity. Furthermore, there are only a few case reports in literature on the association of these masses with cancer. We present a case of a G. lamblia-filled pancreatic cystic mass in a patient with a history of T-cell-rich B-cell lymphoma. The authors performed a PubMed search using (Medical Subject Headings) MeSH terms of pancreas, mass, Giardia, and lymphoma.  A 53-year-old male with past medical and surgical history of T-cell-rich B-cell lymphoma, status post R-CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisone plus rituximab) therapy with positron emission tomography (PET) scan showing no residual disease, essential hypertension, and alcohol use disorder presented to the emergency department (ED) with epigastric pain and nausea for one week. Computed tomography (CT) scan of the abdomen showed a 2.3 cm hypodense pancreatic cystic mass. This was a new finding when compared to his prior abdominal imaging. Fine needle aspiration (FNA) biopsy of the mass showed lymphocytes, reactive atypical epithelial cells, and numerous organisms consistent with Giardia lamblia. He was treated with metronidazole 250 mg by mouth three times a day (TID) for five days. Follow-up magnetic resonance imaging (MRI) and magnetic resonance cholangiopancreatography (MRCP) showed complete resolution of the pancreatic mass. There are only a few case reports on G. lamblia in the pancreas. The pathologist indicated sheets of numerous Giardia in the sample, making small bowel contamination less likely and G. lamblia aspirate from the pancreas more probable as the source. The authors hypothesize that this patient may have had chronic G. lamblia infection as a potential cause for the T-cell-rich B-cell lymphoma manifestation. The patient reported travel to an area with possible exposure to G. lamblia one year prior to presentation with the lymphoma. During that time he had increasing abdominal pain, intermittent chronic diarrhea, and weight loss. G. lamblia's mechanism of action has been theorized to involve induction of pro-apoptotic factors, intestinal barrier dysfunction, up-regulation of cell-cycle genes, and crypt hyperplasia.  The mechanism of action of pancreatic masses filled with G. lamblia and the association of G. lamblia and cancer is not completely understood. Further research is required to better understand these possible phenomena as it can help us better comprehend G. lamblia, its associations, and new cancer etiologies.