IMT is a rare special type of disease, which was first reported in the lungs8,9, the name IMT is often termed differently in primary research, including plasma cell granuloma, plasma cell pseudotumor, inflammatory pseudotumor, inflammatory fibroxanthoma and histiocytoma10. IMT can occur almost anywhere in the body, including lungs, liver, bladder, mesenteric, neck11-13. However, IMT arising from the pancreas are extremely rare. To date，only 29 cases have been reported in the English literature. We conducted a brief literature review of reported cases with pancreatic IMT so as to better understand the pancreatic IMT , as summarized in Table 15,10,14-34. Of these cases 20 were male（20/29, 69%） and 9 were female （9/29, 31%） with obvious male predilection. The tumor diameter for all reported cases ranged from 1.5 to 15 cm. Almost tumors were pancreatic head (21/29 patients) followed by the pancreatic tail (4/29 patients) or pancreatic body (3/29 patients), which may represent that pancreatic IMT was more common in pancreatic head, however, more evidence is required.
Pancreatic IMT can occur at all ages, but prefer children and young adult35. We found in the English literature that the age range for all reported cases is from 6 months to 82 years (mean age 42 years). The current patient is 66 years old, which matches the age reported in the literature.
As described previously, the clinical presentation caused by pancreatic IMT varies depending on its anatomic location, from asymptomatic to hemorrhagic shock due to rupture of the spleen19,22. Almost all of pancreatic IMT have similar nonspecific symptoms regardless of their site of tumor, that is, abdominal discomfort, abdominal distension, abdominal pain, general fatigue and wight loss have also been recorded at the time of presentation. Obstructive jaundice may be noted in typical patients with pancreatic head IMT. It can also obstruction of the pancreatic duct and induced chronic pancreatitis with abdominal discomfort, diarrhea, and indigestion23. The IMT arising from the pancreatic tail also can obstruction of blood vessels of the spleen, resulting in rupture of the spleen with severe abdominal pain and hemorrhagic shock22. However, our patient was located at the neck of the pancreas, she came to the hospital without any special symptoms.
The preoperative laboratory findings of pancreatic IMT were nonspecific for diagnosis of disease. Only few patients with a solitary mass occurring in the head of the pancreas may be elevated in both serum total bilirubin, amylase, and carbohydrate antigen 19-9 due to obstruction of the bile duct or pancreatic duct26. The radiological features are often deceptive. Ultrasound, CT and MRI examinations show a mass lesions mimicking pancreatic cancer or pancreatic neuroendocrine tumor. Also similar to other malignant tumors, whole body 18F-FDG PET/CT also showed elevated SUVmax36, this feature can distinguish IMT from non-neoplastic lesions, such as pancreatic pseudocyst, swollen lymph nodes. In addition, whole body 18F-FDG PET/CT are best tools in detection of tumor recurrence or distant metastasis. More interestingly, even with standard intraoperative frozen pathology may not provide definitive information to distinguish pancreatic IMT from pancreatic inflammatory pseudotumor.
The definitive diagnosis of IMTs rely on histological evaluations and immunohistochemical tests 37. The histological features of IMTs are spindle-shaped cells accompanied by varying degrees of inflammatory cell38,39. Coffin et al. suggested that clonal cytogenetic abnormalities involving the anaplastic lymphoma kinase (ALK) gene on the short arm of chromosome 2 at 2p23, which occur in approximately 50% of IMTs 37, its can be a useful test in the definitive clinicopathologic diagnosis and when positive. In addition, most extrapulmonary IMTs display immunohistochemical reactivity for SMA, Desmin, tissue cell marker CD68 and vascular markers CD3440.
To date, no standard consensus regarding the treatment of pancreatic IMT has been established. However, almost all of authors have recommended surgical resection of the lesion as the primary therapeutic option for pancreatic IMT. This was based on the analysis of 29 cases of pancreatic IMT. The surgical approach is related to the location of the lesion on the pancreas. For pancreatic head IMT, a pancreaticoduodenectomy is recommended, while a distal pancreatectomy is recommended for pancreatic body or tail IMT. Pancreatic IMT often invasion surrounding organs, such as colon, duodenum, stomach, surgery with invasion of adjacent organ may remain the therapeutic option. However, no widely accepted theory exists for such low-grade malignant lesions, whether radical surgery is necessary or not requires a large number of further clinical studies to be verified. Radiation therapy, chemotherapy and high-dose steroid therapy have also been used in patients who resection is neither complete nor possible or in patients with malignant disease status postsurgical resection20,28,41. The spontaneous regression of pancreatic IMT has been reported only infrequently28. Given that our patient was an elderly, infirm female who had pancreatic neck IMT only, sparing the head and body, MDT discussion suggests that enucleation may be more benefit therapeutic option. No adjuvant treatment was administered following enucleation of pancreatic IMT, the patient remained symptom-free and healthy without evidence of recurrence tumor or metastasis was observed during the ten months following surgery. Although there is only 1 reported case of surgical measure with enucleation in patients with IMT, such surgical measure could be considered in the future. Further accumulation of cases is required to explore the surgical measure of pancreatic IMTs.
Pancreatic IMT regarded as low-grade malignancy, the prognosis is generally favorable. However, its exhibits the potentiality of malignancy, distant metastasis and recurrence, close and long-term follow-up after surgery must be carried out.