Standardized pathology assessment of distal pancreatectomy specimens, an explanatory video as performed in the DIPLOMA trial. Pancreatic ductal adenocarcinoma is associated with a poor prognosis. A minority of these tumors are found in the pancreatic body and tail.
Accurate pathological assessment of pancreatic specimens is essential for the provision of prognostic information that may guide treatment strategies. The following protocol focuses on the assessment of left pancreatectomy specimens, including specimen orientation, inking, lymph node sampling, and block selection. A 79-year-old woman presented with an incidental finding of a 34-millimeter tumor within the body of the pancreas with adjacent lymphadenopathy suspicious for malignancy on CT scan.
No distant metastases seen. A radical left pancreatectomy, splenectomy, and wedge resection of the stomach was performed. CT scan demonstrates the tumor within the pancreas.
Following surgery, the specimen is fixed in formalin for 24 to 48 hours. Macroscopic assessment of left pancreatectomy specimens includes specimen orientation, measurement of pancreas, spleen, and upper organs, inking of margins and peritonealized surfaces, specimen dissection, and assessment of tumor location, size, appearance, and approximate distance to margins and tissue sampling. With regards to specimen orientation, formalin fixation may cause distortion, making it difficult to distinguish the anterior peritonealized surface from the retroperitoneal or posterior dissection margin.
For these reasons, it is recommended that the operating surgeon places sutures to mark the posterior margin, as is done in this case. This is the anterior peritonealized surface and this is the stapled transection margin where the splenic vessel margins lie. This is the posterior dissection margin, which is marked with a suture.
This is the superior border of the pancreas where the splenic artery and vein lie and this is the inferior border of the pancreas. This is an additional stapled gastric wall margin and this is the spleen. Specimen dimensions.
The pancreas measures 95 millimeters from medial to lateral, 30 millimeters cranial to caudal, and 20 millimeters anterior to posterior. The spleen is 110 millimeters cranial to caudal, 60 millimeters anterior to posterior, and 20 millimeters medial to lateral. The wedge of stomach measures 35 by 10 by five millimeters.
The specimen is inked in the following manner. The anterior peritonealized surface is inked yellow. The gastric wall margin is inked blue.
The transection margin is inked red. The superior border of the pancreas is inked in green in order to identify station 11 lymph nodes. The inferior border is inked in orange in order to identify station 18 nodes and the posterior dissection margin is inked in black.
Before dissecting the specimen, the transection margin and vascular resection margins are taken. The staple line of the transection margin must be removed as metal staples cannot be cut by the microtome blade. It is advised to cut closely to the staple line to preserve as much as possible the proximity to the true margin.
Having removed the staple line, the transection margin can either be assessed with a single en face section or alternatively bread slices can be made perpendicular to the original staple line so as to measure exact distance of tumor to margin. The splenic artery and vein are in close proximity to the transection margin and are usually marked with clips. An en face section is taken at both artery and vein.
Any additional resection margins can now be removed. In this case, we removed the staple line from the gastric wedge resection. Finally, specimen dissection can begin.
The pancreas is sliced from medial to lateral at three to five-millimeter intervals towards the splenic hilum. It is strongly advised not to remove any of the posterior pancreatic fat. The slices are laid out from medial to lateral in 15 slices.
And now for tumor assessment. Here we show that tumor is present in slices nine to 14. The cut surface of the tumor is pale and homogenous.
Tumor measures 30 millimeters to the craniocaudal plane, 25 millimeters anterior to posterior, and 30 millimeters medial to lateral. The third measurement is based on slice thickness. Macroscopic assessment of tumor size can be challenging owing to the presence of fibrosis and chronic pancreatitis that can mimic tumor macroscopically.
It is for this reason that a generous amount of tumor sampling, supported by a detailed block description with photographs of the specimen slices, can be used to achieve more accurate description of tumor size and extent, which can then be correlated microscopically. Within the specimen slices, one can see the splenic artery running along the superior border of the pancreas. The splenic vein, though harder to visualize in this image, runs along the posterior border of the pancreas, halfway through the slice.
Though tumor is seen in close vicinity to the splenic vein, microscopically it was not involved. When sampling tumor, the specimen slices are geometrically divided to include surrounding peripancreatic fat and lymph nodes, demonstrating the relationship of tumor to adjacent structures and margins. Furthermore in this case, sections demonstrating the exact relationship between tumor and the gastric wall are taken.
Pancreatic ductal adenocarcinomas have an infiltrative pattern of growth, where the interface between tumor and normal pancreas can be obscured by fibrosis and chronic pancreatitis. Therefore, the same rationale for thorough block taking applies for assessing margins. Spleen is now bread sliced in the craniocaudal direction at three to five-millimeter intervals.
In instances where tumor is in close proximity to the spleen, it is recommended to keep the spleen intact with the specimen and take sections in continuity between tumor and spleen. Assuming there are no focal abnormalities, a representative section is taken of the spleen. Finally, we have block selections, which includes the transection margin, vascular resection margins, gastric wall margins, blocks of tumor demonstrating maximum size and distance to margins, background pancreas and a representative section of spleen, and lymph nodes.
The microscopic findings were of a 30-millimeter, moderately differentiated ductal adenocarcinoma, with extension into the muscularis propria of the gastric wall. There was lymphovascular invasion without involvement of the splenic artery or splenic vein and perineural invasion. Three out of 17 lymph nodes were involved, one superior and two inferior.
Staging was pT2, N1 according to TNM8, and all margins were clear by at least one millimeter. The advantages of the methodology described include the use of orientation sutures to mark the posterior dissection margin. This method of orientation is part of the standardized protocol for the DIPLOMA trial.
Secondly, we strongly advised to avoid removing the posterior peripancreatic fat as this may compromise accurate margin assessment. In addition to inking the margins, using different colors to mark the superior and inferior border of the pancreas allows us to identify the station 11 and 18 lymph nodes.
