Low frequency of molecular changes and tumor recurrence in inverted papillomas of the urinary tract.
OBJECTIVE
Inverted papilloma (IP) of the urinary tract can be difficult to distinguish from noninvasive urothelial carcinoma with prominent inverted growth pattern (invNIUC). Ancillary markers may help to resolve such cases and clarify the reported malignant potential of some IPs.


METHODS
Eighty-nine urothelial lesions initially diagnosed as IP were reviewed by 4 experienced urologic pathologists and studied immunohistochemically (Ki67, p53, CK20, MSH2, MLH1, and MSH6). Mutations of the FGFR3 gene, deletions (loss of heterozygosity) of 9p, 9q, and 17p, microsatellite instability, and elevated microsatellite instability at selected tetranucleotides were also analyzed.


RESULTS
Considerable interobserver variability in histopathologic diagnoses was noticed. Only 62 (69.7%) initial diagnoses were confirmed by the review pathologists whereas 23 tumors (25.8%) were redefined as invNIUC. Molecular analyses revealed infrequent alterations in IPs, including microsatellite instability (1.8%), elevated microsatellite instability at selected tetranucleotides (13.2%), FGFR3 mutations (9.8%), 9p deletions (3.9%), 9q deletions (13.2%), 17p deletions (5.1%), nuclear p53 accumulation (18.9%), and aberrant immunostaining for MSH2 (5.8%), MLH1 (11.8%), and MSH6 (3.8%). IP and invNIUC differed in FGFR3 mutations and Ki-67 labeling index (P<0.001 each), and 9q loss of heterozygosity (P=0.03). There were fewer recurrences in IP (5.4%) compared with invNIUC (40.9%; P<0.0001).


CONCLUSIONS
IP is a benign lesion that lacks specific genetic alterations found in exophytic noninvasive papillary urothelial tumors. These lesions could be reactive in nature, perhaps secondary to chronic inflammation or a neoplastic process that lack specific genetic alterations. Nevertheless given the clinical and molecular data of this study a conservative clinical approach is appropriate.
Eiber
Matthias
M
Institute of Pathology, University of Regensburg, Regensburg, Germany.
van Oers
Johanna M M
JM
Zwarthoff
Ellen C
EC
van der Kwast
Theo H
TH
Ulrich
Oehler
O
Helpap
Burkhard
B
Stoerkel
Stephan
S
Blaszyk
Hagen
H
Cheville
John
J
Sauter
Guido
G
Wild
Peter J
PJ
Stoehr
Robert
R
Hofstaedter
Ferdinand
F
Hartmann
Arndt
A
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis; D002277:Carcinoma / Q000473:pathology; D004252:DNA Mutational Analysis; D003937:Diagnosis, Differential; D006801:Humans; D007150:Immunohistochemistry; D019656:Loss of Heterozygosity; D018895:Microsatellite Repeats; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology*; D015588:Observer Variation; D018308:Papilloma, Inverted / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D016133:Polymerase Chain Reaction; D051498:Receptor, Fibroblast Growth Factor, Type 3 / Q000235:genetics; D014571:Urologic Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*
D014408:Biomarkers, Tumor; C496365:FGFR3 protein, human; D051498:Receptor, Fibroblast Growth Factor, Type 3