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Particular tumor of the pancreas: A case report

BACKGROUND Granular cell tumor (GCT) of the pancreas is a rare neurogenic tumor. The first case of pancreatic GCT was described in 1975, and up to now, only 7 cases have been reported. CASE SUMMARY A 53-year-old male had a pancreatic mass for 1 mo. He was not treated at the local hospital, but referred to Henan Tumor Hospital for surgery. Preoperative imaging revealed a 2.0 cm × 2.5 cm-sized mass located in the body of the pancreas. At the microscopic level, a large number of eosinophilic particles are present in the oval tumor cells. The immunohistochemistry of this tumor cell display CD56 (+), blood vessels CD34 (+), Ki-67 (+) < 10%, and S-100 (+). CONCLUSION GCT of the pancreas should be recognized as a preoperative differential diagnosis of pancreatic tumors. Surgical resection of the tumor should be attempted; however, GCT of the pancreas has a certain rate of tumor metastasis and recurrence. Therefore, GCT of the pancreas requires regular and long-term follow-up.


INTRODUCTION
Granular cell tumors (GCTs) arise from Schwann cells[1] and have been located almost everywhere in the body, including visceral or cutaneous locations [2], chest wall regions [3], and in the oral cavity [4], pituitary, central nervous system [5], and respiratory system [6]. Granular cells contain unique acidic protein, S-100 protein, which is present in Schwann cell and satellite cells of ganglia. GCTs of the pancreas are so extraordinarily rare that only 7 cases have been reported in all literatures. Now we report the eighth case of pancreatic GCT, including clinical, imageological, and histological features.

Chief complaints
A 53-year-old male patient was referred to our hospital after a physical examination 1 mo earlier revealed a mass in his pancreas.

History of present illness
There's nothing special about his past medical history.

History of past illness
The patient's past medical history is unremarkable.

Physical examination
The patient's skin and sclera were not yellowish, abdominal muscles were not tense, with/without tenderness and rebound pain. The patient's liver and spleen were not palpable under the ribs, and the entire abdomen was not palpable. Murphy's sign was negative. Percussion and auscultation in the abdomen were normal.

Laboratory examinations
Serum tumor marker (carbohydrate antigen 19-9: 15.73 KU/L) was moderately elevated. The liver and kidney function were within the normal range, and the other biochemical tests were within the normal range. Urine analysis results were also normal. An electrocardiogram, chest radiograph and arterial blood gas tests showed no abnormalities.

Imaging examinations
On T1-weighted magnetic resonance imaging (MRI), the tumor in the head of the pancreas showed mild, low signal intensity ( Figure 1A). On the contrary, the peripheral tissues around the tumor were equal signal while the central area of tumor was hypointense on the T2-weighted image ( Figure 1B). The portal vein was not invaded by the pancreatic head tumor, neither was celiac artery.

Further diagnostic work-up
After coming to our hospital, the tumor was assessed by abdominal ultrasound test, and a hypoechoic area whose size was 25 mm × 25 mm was identified. The morphological structure was normal and the boundary was clear in the body of the pancreas. Electronic gastroscope showed a duodenal bulb compressional bulge and surface October 26, 2021 Volume 9 Issue 30

Preoperative diagnosis
The diagnosis prior to operation was pancreatic tumor of unknown properties.

FINAL DIAGNOSIS
Postoperative pathological results and immunohistochemical results indicated pancreatic GCT.

TREATMENT
In view of the above results, the patient was diagnosed with a pancreatic tumor and a pancreatoduodenectomy was performed. Laparotomy showed that the tumor was hard, located in the pancreatic head, with oppression of the duodenum, and was about 3.0 cm × 2.5 cm × 2.0 cm. No capsule was evident around the tumor. Common bile duct was mildly expanded to a diameter of about 1.2 cm and full of green turbidity bile. Gall bladder, intestinal canal, and omentum majus had mutually tight adhesion. There were no metastatic lesions found on the adjacent organs and peritoneum. No swelling lymph nodes were seen around the lesion location. Histological examination confirmed that the tumor was completely removed and the margin of the resection specimen was negative for tumor cells. None of 4 regional lymph nodes examined showed metastasis. After 2 wk of receiving anti-inflammatory, compensation fluid, nutritional therapy, and symptomatic treatment, the patient was discharged from the hospital free of symptoms.

OUTCOME AND FOLLOW-UP
The patient recovered smoothly after surgery, and the postoperative condition was not unstable. The patient was asymptomatic during the 2 years of follow-up after the operation. The patient was advised to continue to follow-up every 3 to 6 mo.

DISCUSSION
The first report of GCT, localized in the skeletal muscle of the tongue, was in 1926 by Abrikossoff. GCT is a rare tissue tumor derived from Schwann cells. Despite reports that GCTs can be localized anywhere in the body, GCTs of pancreatic origin are rare. The characteristics of the 7 previously reported cases of pancreatic GCT are summarized in Table 1. By reason of the rarity of pancreatic GCT, its epidemiology, clinical symptoms, imaging findings, and serological examination have not been clarified. Therefore, it is difficult to distinguish pancreatic GCT from pancreatic tumor, including pancreatic cancer, pancreatic neuroendocrine tumor, pancreatic cystadenoma, and cystadenocarcinoma. Their clinical manifestations are not typical. On CT and MRI examination, the tumors are round, oval or dumbbell cystic lesion whose cystic wall is thickness. There are some fences that can be obviously enhanced during dynamic CT and MRI inside of cystic lesion. In the past, some experts thought that GCT was benign tumor, as the majority of GCTs are benign However, increasingly the literature has indicated that GCT has some characteristics of malignant tumors, such as metastasis and recurrence, despite having a benign histological appearance. In fact, only about half of reportedly malignant cases, whose incidence is only 1% to 2%, are diagnosed with metastases [7,8]. Previous cases of GCT metastasis to liver, lung, brain, bone, abdominal wall, pancreas, and other sites have been reported [9][10][11][12][13][14][15]. Morphological examination cannot predict the biological behavior of GCT. However, when the tumor shows local recurrence, invasive growth, rapid growth over a short period, or a diameter greater than 4 cm, we should be highly alert to the possibility of malignancy. In our patient, diffuse oval tumor cells were seen histopathologically in the presence case of GCT and lots of eosinophilic granules exist in the cytoplasm of tumor cells (Figure 3). Periodic Acid-Schiff staining ( Figure 4A), staining for S-100 protein, and neuron specific enolase by immunohistochemistry in GCT cells were positive, which further support for the diagnosis of GCT ( Figure 4B). However, it was not easy to make an accurate preoperative diagnosis of pancreatic GCT, because GCT is so rare that its characteristics have been fully elucidated. Not all of the pancreatic GCT can be accurately diagnosed. Among the 7 cases of pancreatic GCT reported in the past, 4 cases of pancreatic GCTs which were misdiagnosed as pancreatic cancer and subsequently surgically removed [16][17][18]. Given that we did not know enough about imaging characteristics of pancreatic GCT, we also misdiagnosed the case as pancreatic tumor. As far as we know, no literature on the MRI features of pancreatic GCTs has been reported. According to the past literature, the MRI characteristic of GCT are different according to the location, for example, Jagannathan[19] described a GCT of the breast showing as slightly hyperintense lesion in T2 weighted [19], on the contrary, Kudawara et al [20] described a case of GCT that shows hypointense signal on a T2weighted image [20]. These findings of MRI in other locations were not fully consistent with our report, and therefore we cannot reach an unified conclusion about the MRI characteristics of GCT to suite for all locations. It has been reported that endoscopic ultrasound-or CT-guide fine-needle aspiration, not the most reliable method, may be helpful in diagnosis of pancreatic GCT [21,22], histopathological testing of the tissue specimen is the gold standard for the final and exact diagnosis. Complete resection of   the lesion was the main treatment for our patient, and the prognosis is for him is good. However, malignant GCTs has about 32% recurrence rate [23], so postoperative followup on a regular basic is also very important.

CONCLUSION
We diagnosed and treated a case of pancreatic GCT. By imaging examination, we founded a tumor located in patient's pancreatic head. Subsequently, the patient underwent a surgery and the tumor was completely removed. Finally, the pathology inspection confirmed that the tumor was pancreatic GCT. Because pancreatic GCT is a rare disease, it is quite difficult to make an accurate preoperative diagnosis. In future, we should consider this possibility of the pancreatic GCT in the differential diagnosis in any pancreatic tumor that is less enhanced than the pancreas regardless of pancreatic duct obstruction.