title: Diagnostic utility of arborizing stromal meshwork fragments in mucinous tumors.
abstract: BACKGROUND
  Arborizing stromal meshwork fragments (ASMFs) have been proposed as a useful clue to differentiate mucin associated with mucinous adenocarcinoma from contaminating mucus during endobronchial ultrasound-guided transbronchial needle aspiration. Our aim was to retrospectively review cytology cases with mucinous material to determine the utility of ASMFs in diagnosing mucinous tumors.
  
  
  METHODS
  Diff-Quik stained smears from archival cytology cases (N = 40) were reviewed, including adenocarcinomas with mucinous features, cystic mucinous neoplasms, and control cases with mucin contamination. Specimens were procured by image-guided fine needle aspiration (FNA) (16 cases), endoscopic ultrasound-guided FNA (22 cases), pathologist-performed FNA (1 case), and fluid drainage (1 case). All cases were reviewed for ASMFs, which were defined as metachromatic, spidery extensions with frayed edges within a background of mucinous material.
  
  
  RESULTS
  ASMFs were identified in 4 (10% of cases, 14% of adenocarcinomas) cases of metastatic gastrointestinal mucinous adenocarcinomas in various locations (liver, lymph node, lung, and bone), but absent in mucin contamination. ASMFs in Diff-Quik stained smears were magenta-colored and corresponded to intervening stroma between dissecting mucin in the tumor. Nonarborizing desmoplastic stroma, inspissated mucus, cartilage fragments, transgressing vessels in renal cell carcinoma, and mucus-like material in pancreatic pseudocysts can morphologically mimic ASMFs.
  
  
  CONCLUSIONS
  These data show that ASMFs may be encountered in some (14%) cases of adenocarcinoma with mucinous differentiation. When present, ASMFs can be diagnostically helpful to differentiate adenocarcinoma with mucinous features from contaminating mucus, if reliably distinguished from mimics. Diagn. Cytopathol. 2016;44:805-810. © 2016 Wiley Periodicals, Inc.
authors: Department of Pathology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors: Stell
authors: S
authors: Patadji
authors: Department of Pathology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors: Joshua
authors: J
authors: Pantanowitz
authors: Department of Pathology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.
authors: Natalie M
authors: NM
authors: Perlov
authors: Department of Pathology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania. monacose@upmc.edu.
authors: Sara E
authors: SE
authors: Monaco
mesh_terms: D002288:Adenocarcinoma, Mucinous / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D061765:Endoscopic Ultrasound-Guided Fine Needle Aspiration; D005260:Female; D005770:Gastrointestinal Neoplasms / Q000473:pathology*; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009093:Mucus / Q000166:cytology
keywords: arborizing stromal meshwork fragments; cytology; cytopathology; mucin; mucinous; stroma