title: The vascular architecture of renal cell carcinoma in fine-needle aspiration biopsies. An aid in its distinction from hepatocellular carcinoma.
abstract: BACKGROUND
  The morphologic similarities between renal cell carcinoma (RCC) and hepatocellular carcinoma (HCC) can cause diagnostic difficulty in fine-needle aspiration biopsy (FNAB) specimens. In the authors' prior study of liver FNAB, peripherally wrapping endothelium (PE) and arborizing transgressing endothelium (TE) were 100% specific for HCC relative to metastatic tumors, which included only three RCCs. In this study, the vascular patterns of RCC in FNAB were reviewed for comparison with HCC, to determine their usefulness in the differential diagnosis of HCC and RCC.
  
  
  METHODS
  FNAB of 49 RCCs (26 primary and 23 metastatic) from 46 patients were reviewed. Four vascular patterns were assessed: PE, TE, papillary endothelium (PAP) in fibrovascular cores of papillary fragments, and short nonbranching endothelium (SE) in small cell clusters. Each pattern was given a semiquantitative score: absent (0), focal (1), or extensive (2). Cellularity was categorized as low (< 20 groups), moderate (20-50 groups), or high (> 50 groups).
  
  
  RESULTS
  Vessels were present in 19 of 26 (73%) primary and 9 of 23 (39%) secondary RCC. PE was not identified. TE was observed in 11 primary (42%) and 7 metastatic (30%) RCC. SE was present in 5 primary (19%) and 1 metastatic (4%) RCC. The TE and SE patterns were distributed among the clear cell, granular cell, and chromophobe RCC. PAP was observed in all four papillary RCC. The majority of the TE and all of the PAP were present in moderately to highly cellular FNABs, whereas SE was usually observed in FNABs with low cellularity.
  
  
  CONCLUSIONS
  FNAB specimens of RCC commonly contain TE, as in HCC, but lack PE. TE was less frequent in metastatic than primary RCC. Other vascular patterns (SE, PAP), absent in HCC, were observed infrequently. Vascular patterns, especially PE, are useful in distinguishing HCC from RCC.
authors.affiliation: Department of Pathology, Massachusetts General Hospital, Boston 02114, USA.
authors.forename: M
authors.initials: M
authors.lastname: Weir
authors.forename: M B
authors.initials: MB
authors.lastname: Pitman
mesh_terms: D001707:Biopsy, Needle; D006528:Carcinoma, Hepatocellular / Q000098:blood supply*; D002292:Carcinoma, Renal Cell / Q000098:blood supply* / Q000556:secondary; D003937:Diagnosis, Differential; D006801:Humans; D007680:Kidney Neoplasms / Q000098:blood supply* / Q000473:pathology; D008113:Liver Neoplasms / Q000098:blood supply*