Pancreaticoduodenectomy for preservation of fat-replaced pancreatic body and tail tissue in a patient with solid pseudopapillary neoplasm: a case report

Background There is no standard surgical method for treating pancreatic head tumors with fat replacement of the pancreatic body and tail. Total pancreatectomy procedures are usually performed to excise pancreatic head tumors and lead to endocrine function loss and subsequent development of diabetes. We present a rare case where the adipose tissue was preserved during pancreaticoduodenectomy in a patient with a solid pseudopapillary neoplasm and fat-replaced pancreatic body and tail. Case presentation Contrast-enhanced computed tomography scans of a 43-year-old man revealed a tumor measuring approximately 3 cm in size with calcification in the pancreatic head. Magnetic resonance cholangiopancreatography showed that the pancreatic ducts in the body and tail were completely disrupted. Furthermore, endoscopic ultrasonography showed no pancreatic parenchyma in the body and tail of the pancreas, with disruption in the main pancreatic duct. Endoscopic ultrasonography-guided fine-needle aspiration led to the final pathological diagnosis of a solid pseudopapillary neoplasm, and laparoscopic total pancreatectomy was performed. However, intraoperative findings indicated that the tumor was located in the pancreatic head. Pancreatic parenchyma was not observed in the pancreatic body or tail, as it had been completely replaced with adipose tissue. Nevertheless, the shape of the pancreas was identifiable. Therefore, pancreaticoduodenectomy was performed to transect parenchyma at the pancreatic neck, while preserving the adipose tissue present in the pancreatic body. The main pancreatic duct could not be identified at the cut surface. Therefore, we performed modified Blumgart-style pancreaticojejunostomy to cover the cut end instead of reconstructing the pancreatic duct. The patient was discharged on postoperative day 12 without complications and is being followed-up as an outpatient. His fasting blood sugar and hemoglobin A1c levels according to the National Glycohemoglobin Standardization Program reports were within normal limits, indicating that the endocrine function (insulin secretion ability) was preserved during the 1.5 years following surgery. Conclusions In patients with pancreatic head tumors, pancreaticoduodenectomy that preserves fat-replaced pancreatic body and tail tissues can preserve postoperative endocrine function.


Background
The most appropriate surgical method for patients with a pancreatic head tumor and fat-replaced pancreatic body and tail has not been established [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Essentially, total pancreatectomy (TP) is performed to excise the pancreatic head tumor, which results in subsequent loss of endocrine function and development of diabetes. Here, we report on a novel case in which adipose tissue was preserved during pancreaticoduodenectomy (PD) in a patient with a solid pseudopapillary neoplasm (SPN) and fat-replaced pancreatic body and tail. Preservation of the adipose tissue enabled retention of postoperative endocrine function and insulin secretion ability. Considering the novelty of our case, we also conducted a literature review of current evidence to gain insights into the procedural approaches in similar cases.

Case presentation
The medical examination of a 43-year-old man revealed calcification in the pancreatic head. He was referred to the Department of Gastroenterology for examination. No symptoms were evident, and his medical history was unremarkable. Contrast-enhanced computed tomography (CT) scans revealed a tumor (approximate size, 3 cm) with calcification in the pancreatic head. The pancreatic duct and parenchymal tissue were not observed on the caudal side of the portal vein. There were no liver metastases or enlargement of the surrounding lymph nodes. T1-weighted magnetic resonance imaging (MRI) scans showed low signal intensity, while T2-weighted MRI scans showed a reasonably high signal intensity in the pancreatic head. Furthermore, T2-weighted MRI scans indicated a high signal intensity in the pancreatic body and tail. Magnetic resonance cholangiopancreatography (MRCP) revealed that the pancreatic ducts of the pancreatic body and tail were completely disrupted (Fig. 1). Endoscopic ultrasonography (EUS) showed a low echoic mass with calcification, while contrast-enhanced harmonic EUS (CH-EUS) (Sonazoid, GE Healthcare, Oslo, Norway) revealed stark contrasts and hypovascularity in the tumor. EUS-guided fine-needle aspiration (EUS-FNA) was performed. Subsequently, the patient was diagnosed with a SPN.
Initially, we planned to perform a laparoscopic TP as intraoperative findings indicated that the tumor was present in the pancreatic head. Additionally, there was no pancreatic parenchyma in the pancreatic body, while that in the tail was completely replaced by adipose tissue. However, the shape of the pancreas could be identified. Based on these findings, a PD was performed on the left side of the portal vein (Fig. 2). As we found that the tumor had invaded the portal vein, we switched to open surgery. The pancreatic duct was not reconstructed, as the main pancreatic duct could not be identified at the cut surface. Therefore, only a modified Blumgart-style pancreaticojejunostomy was performed to cover the cut end. The surgery lasted for 425 min, and the volume of blood loss was 500 mL. Histopathological findings indicated that the pancreatic tissue was replaced by adipose tissue, and only Langerhans islets were observed (Fig. 3).
The patient was discharged on postoperative day 12 without complications. He is being followed-up 1.5 years after the surgery. His fasting blood sugar and hemoglobin A1c (HbA1c) levels according to the National Glycohemoglobin Standardization Program (NGSP) reports were within the normal limits (HbA1c NGSP, preoperatively, 5.5%; 3 months postoperatively, 5.7%), indicating that endocrine function (insulin secretion ability) was preserved. He experienced diarrhea three times a day after the surgery; however, his nutritional status was maintained with oral administration of pancrelipase. His preoperative body weight and serum albumin levels were 87.6 kg and 4.6 g/dL, respectively, and by 3 months postoperatively, these were 81.4 kg and 4.6 g/dL, respectively.

Conclusions
Studies have reported that approximately 60% of patients with congenital aplasia in the body and tail of the pancreas develop diabetic complications [15]. Takahashi et al. [16] reported that atrophy and vitrification of the Langerhans islets were noted in autopsy cases of earlyonset congenital aplasia in the body and tail of the pancreas, whereas an increased number of Langerhans islets and hypertrophy were found in some late-onset cases. Thus, diabetes mellitus in congenital aplasia of the body and tail of the pancreas is not caused by a single factor, but rather by the lack of Langerhans islets and several other acquired factors [16].  An electronic search in the Japan Medical Abstracts Society database (Ichushi web) using the phrases "agenesis of dorsal pancreas," "aplasia of the pancreatic body and tail," "dysplasia of the pancreatic body and tail," and "hypoplasia of pancreatic body and tail" (excluding proceedings) yielded 91 case reports published since 1990. In 14 [1][2][3][4][5][6][7][8][9][10][11][12][13][14] of the 91 reports, the patients had undergone either TP or PD (Table 1). In TP cases, six patients developed diabetes before surgery and two patients developed diabetes after surgery. However, in PD cases (n = 6), patients did not develop diabetes at all. The loss of pancreatic tissue in the body and tail of the pancreas was noted in most patients who underwent TP; however, adipose tissue replacement of pancreatic tissue was not observed in any of these patients. Patients who underwent PD had no remnant pancreatic tissue, but did have adipose tissue, with the remaining Langerhans islets having replaced the lost pancreatic tissue.
These results suggested that the Langerhans islets were retained in cases with adipose tissue replacement, which preserved endocrine function; thus, the patients did not develop diabetes. Therefore, we believed that performing PD with retention of fat-replaced pancreatic body and tail tissues in patients with pancreatic head tumors can preserve postoperative endocrine function. In addition, we performed a literature search for the reported procedures aimed at preserving adipose tissue in the pancreatic body and tail after PD. Tobita et al. [10] reported a patient with hypoplasia rather than agenesis of the dorsal pancreas. Furthermore, they found a main pancreatic duct requiring pancreaticojejunostomy. However, postoperative pancreatic juice leakage was observed. In our case, complete fat replacement of the pancreatic body and tail preserved the shape of the pancreas, but the main pancreatic duct could not be identified. Therefore, a modified Blumgart-style pancreaticojejunostomy was performed to prevent pancreatic juice leakage. In addition, our literature review did not reveal any cases with anastomosis in the presence of fat-replaced pancreatic body and tail tissues, as performed in our case. Furthermore, postoperative pancreatic juice leakage was not observed in our case. These observations suggest that in cases where the remaining pancreatic tissue is completely replaced by adipose tissue and the main pancreatic duct is not identifiable, it may not be necessary to perform pancreaticojejunostomy.
In conclusion, in patients with the pancreatic head tumors, pancreaticoduodenectomy that preserves fatreplaced pancreatic body and tail tissues can preserve postoperative endocrine function.