A 71-year-old man was admitted to the hospital for strict glycemic control in June 2020. He had been treated for diabetes mellitus (DM), hepatic hemochromatosis, and bronchial asthma for 15 years. Previously, he had undergone a left adrenalectomy for adrenal neuroma. His glycemic control had deteriorated since April. A pancreatic tumor was identified by US, enhanced CT, and MRI. At the request of his family, he was referred to our hospital in August 2020.
On physical examination, no tumor mass was palpable in his abdomen, except for surgical scars. The results of the laboratory investigations were as follows: RBC, 4.5 × 106/μ; hemoglobin, 9.6 g/dl (normal range: 13.0–17.6); WBC, 3.1 × 103/μ (4.5–9.0 × 103); platelet count, 195 × 103/μ; Fe, 23 μg/dl (49–219); amylase, 89 U/l; trypsin, 1171 ng/ml (100–550); elastase-1, 959 ng/dl (0–300). The results of the liver function tests were within normal limits. The levels of tumor markers were as follows: carcinoembryonic antigen (CEA), 3.0 ng/ml; carbohydrate antigen 19-9 (CA19-9), 20 U/ml; Span-1, 39 U/ml (< 30); NCC-ST-439, 1.2 U/ml (< 4.5); AFP, 2 ng/ml. His pulmonary function was impaired, as shown by the following results: FVC, 3.7 l; FEV1, 1.61 l; FEV1%, 43.5%.
The CT scan showed a slightly enhanced mass, approximately 27 mm in size, in the tail of the pancreas, with dilatation of the distal MPD (Fig. 1a). Magnetic resonance cholangiopancreatography (MRCP) showed mild dilatation (3.5 mm) of the caudal MPD up to the pancreas neck. The distal MPD was dilated to a diameter of 7 mm. In addition, a cystic lesion, a suspected branch duct intraductal papillary mucinous neoplasm (BD-IPMN), was seen in the pancreatic neck (Fig. 1b).
Thin-slice multi-detector row computed tomography (MDCT) in our hospital showed a homogenous slightly enhanced mass with expanded extrapancreatic progression and moderate dilatation of the distal MPD. However, this tumor showed no infiltration pattern to the retropancreatic tissue and splenic vein. Downstream tumor progression in the MPD was observed up to the left side of the portal vein (Fig. 1c, d). These preoperative findings support a diagnosis of PACC or pancreatic neuroendocrine tumor (pNET) rather than pancreatic ductal adenocarcinoma (PDAC).
The EUS findings were as follows: a hypoechoic mass lesion with a lobulated structure approximately 3 cm in size was found in the tail of the pancreas; dilatation of the upstream MPD and a tumor thrombus in the MPD downstream from the main tumor was observed (Fig. 2a, b). EUS-FNA using a 22G needle was performed to obtain specimens for pathological diagnosis. Macroscopic inspection showed whitish fragments. Hematoxylin–eosin (HE) staining showed suspected PACC. The results of the immunohistochemical staining were as follows: chromogranin A (−), synaptophysin (−), CD56 (−), CK7 (+), CK19 (−), β-catenin in the nucleus (−), MIB-1 (20–30%), α1-antitrypsin (+), and B-cell lymphoma/leukemia 10 (BCL-10) (+) (Fig. 2c–e). Based on these results, the pancreatic mass was preoperatively diagnosed as PACC. Figure 3 shows a schematic diagram illustrating the tumor extension based on preoperative imaging.
Considering the preoperative diagnostic evaluations and the patient’s poor physical condition, we scheduled a distal pancreatectomy with a pancreatic dissection line was at the right side of the SMV. A laparotomy was performed. No metastatic lesions were found in the peritoneum or liver. Intraoperative cytological examination was negative for malignant cells. There was no evidence of tumor invasion of the portal venous system or retropancreatic tissue. Distal pancreatectomy with lymphadenectomy in the area of the common hepatic and celiac arteries was performed. The pancreatic neck was transected at the side of the SMV. The postoperative course was uneventful. We presented adjuvant chemotherapy with S1, but the patient refused. There has been no relapse for 5 months postoperative follow-up.
On macroscopic appearance, the tumor was well-circumscribed, and its cut surface showed a solid tumor. The surgical specimen measured 6.8 × 3.3 × 2.3 cm including the MPD tumor extension. The size of the main tumor, except for the MPD extension, was 3.3 × 2.3 × 2.5 cm. The MPD was occupied by the tumor spreading 35 mm to the duodenum (downstream) and 5 mm upstream. The tumor was gray-white and firm. In macroscopic views of the cut surface, continuous tumor extension into the MPD was observed in the pancreatic body (Fig. 4a, b).
Histologically, the solid mass confirmed the PACC diagnosis suspected by the intraductal growth and preoperative evaluation. No tumor infiltration was observed in the epithelium of the main pancreatic duct (Fig. 4c). A tiny main duct intraductal papillary mucinous adenoma (MD-IPMA) was also observed. No vascular or neural invasion was observed. No cancer cells extended to the splenic vein nor was there nodal involvement. There were no cancer cells at the surgical margins. PanIN-3 cells were seen in the branched pancreatic ducts near the MPD (Fig. 4d, e).
Microscopically, the tumor consisted of small round cells with occasional acinar patterns (Fig. 4f). The results of immunohistochemical staining of the resected specimen were as follows: chromogranin A (−), CA19-9 (−), synaptophysin (−), CD56 (−), p53 (< 5%), maspin (−), α1-antitrypsin (+ weak), and MIB-1 (30%, hot spot) (Fig. 4g). The final diagnosis was T3, N0, M0, Stage IIA (Union for International Cancer Control Staging, 8th edition).