Peripancreatic Soft Tissue Involvement by Pancreatic Ductal Adenocarcinomas: Incidence, Patterns and Significance
I Oliva, S Bandyopadhyay, I Coban, O Basturk, N Culhaci, D Kooby, J Sarmiento, C Staley, N Adsay. Emory Univ., Atlanta; WSU, Detroit; NYU, NY
Background: Involvement of peripancreatic soft tissues (PST) is one of the main parameters in the current TNM staging of resected pancreatic ductal adenocarcinoma (PDA); however, defining PST by histologic parameters can be highly problematic due to abundant baseline pancreatic adipose tissue, absence of pancreatic capsule, and difficulty delineating pancreatic lobules, which becomes further blurred in the setting of compression-related secondary changes such as atrophy and fibrosis.
Design: In order to evaluate the true PST involvement by PDA, an orange-peeling method of dissection for pancreatic head resections was devised in which all the PST was shaved-off from the pancreatic surfaces before sectioning the specimen further. The PST was then separated into 7 defined anatomic regions and from each, at least one section was obtained for the purposes of both PST evaluation and also identification of microscopic LNs.
Results: PST involvement in patients with PDA was detected in 103 of 109 (94.5%) when evaluated by this method. In many cases, this appeared to be away from the main tumor, unappreciated by the gross examiners, and in some, PST involvement was represented as small microscopic foci, or scattered isolated solitary ducts (ISD). Many of these ISDs were so well differentiated that they could be easily mistaken for PanINs. Some were surrounded by muscular vessel wall, indicating that they are in fact intravascular tumor cells carcino-endothelializing the inner surfaces of the vessels, and as such representing a peculiar, insidious form of spread into PST. Separately, among these 109 cases, 19 would have qualified as pT1 by stage criteria (<2 cm). However, 16 of these 19 had PST involvement, placing them into the pT3 category instead (by the TNM 6th edition).
Conclusions: PST involvement by PDA is very common (94.5%) when examined by the orange-peeling method. The incidence and subtle patterns of infiltration into PST, such as isolated solitary ducts and carcino-endothelialization, indicates the importance of careful evaluation of these regions, illustrates the highly insidious nature of PDA, and more importantly, provides more insight to the reasons of its incurability. Since PST involvement indicates pT3 in the current TNM staging, it appears that most resected PDAs cannot qualify as pT1 or pT2 if carefully examined.
Category: Liver & Pancreas
Wednesday, March 11, 2009 9:30 AM
Poster Session V # 236, Wednesday Morning