Histopathological and immunohistochemical study of papillary urothelial neoplasms of low malignant potential and grade associated with extensive invasive low-grade urothelial carcinoma.
OBJECTIVE
To report five cases of papillary urothelial neoplasm of low malignant potential (UNLMP) and papillary urothelial carcinoma of low grade (UCLG) associated with extensive muscle invasion, and to investigate the clinical and histopathological presentation and their immunohistochemical properties.


METHODS
Consecutive cystectomy and correlating transurethral resection (TUR) of urinary bladder tumour specimens were reviewed to identify cases of UCLG having extensive invasion into the urinary bladder wall. All specimens were stained immunohistochemically, as were those from 10 control cases having reactive urothelium or superficial UNLMP. The clinical charts were reviewed.


RESULTS
Of a total of 95 cystectomy cases there were four of UNLMP or UCLG with extensive invasion. An additional case was added from our consultation file. All five cases had biopsies misdiagnosed as benign lesions or prostatic adenocarcinoma. The superficial invasive components consisted of UCLG conforming to the previously described entities of nested transitional cell carcinoma (TCC), microcystic or deceptively benign-appearing TCC. Immunostaining for cytokeratin 20, MIB-1 and p53 was similar to reactive epithelia, whereas E-cadherin immunoreactivity was slightly different, with focal negativity compared with extensive immunoreactivity in invasive vs noninvasive UCLG. Four patients developed distant metastases; three died within a follow-up of 3 years.


CONCLUSIONS
UNLMP and UCLG that widely and deeply invade the bladder accounted for 4% of urothelial carcinoma (UC) in cystectomy specimens and commonly pose diagnostic problems in superficial TUR specimens. From this study with few cases the diagnosis of this entity in superficial biopsies is aided by an awareness of it and by identifying 'benign appearing' nests of urothelial cells which are deeply seated in the stroma. Immunostaining is unlikely to be very useful.
Division of Anatomical Pathology, Department of Laboratory Medicine, The Ottawa Hospital Civic Campus, Ontario, Canada. ktmai@ottawahospital.on.ca
Kien T
KT
Mai
Ghazi
G
Elmontaser
D Garth
DG
Perkins
Hossein M
HM
Yazdi
William A
WA
Stinson
Anthony
A
Thijssen
D000368:Aged; D002291:Carcinoma, Papillary / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D012509:Sarcoma / Q000473:pathology*; D001749:Urinary Bladder Neoplasms / Q000473:pathology*; D019459:Urothelium / Q000473:pathology