Urothelial eddies in papillary urothelial neoplasms: a distinct morphologic pattern with low risk for progression.
We encountered an undescribed histologic feature of papillary urothelial neoplasms: "urothelial eddy", which was histologically reminiscent of squamous eddy of irritated follicular keratosis of the skin. A review of 756 patients with transurethral resection of bladder tumor revealed 10 patients (1.3%) of papillary urothelial neoplasms with urothelial eddies. All cases were male with a median age of 65 years. Urothelial eddies were characterized by small ovoid nests of ovoid to spindle cells arranged in an onion-skin pattern with fine cytoplasmic processes within wide intercellular space. The cytoplasmic processes mimicked intercellular bridges but ultrastructurally were cytoplasmic microvillous projections. They were of papillary urothelial neoplasm of low malignant potential in seven patients and low-grade urothelial carcinoma in three patients. Nine patients presented as non-invasive tumor and one patient showed microinvasion within papillary stalks. Six patients showed an inverted growth pattern. Their immunoprofile was more similar to that of conventional urothelial carcinoma rather than squamous cell carcinoma: high expressions of GATA3, S100P, uroplakin III, and cytokeratin 7; and low expressions of high molecular weight cytokeratin and p53. The Ki-67 labeling index was low (mean and median values, 2% each). During the follow-up period (mean, 88.7 months), four patients, including the microinvasive patient, showed recurrence with the same grade and stage but neither progressed into muscle-invasive tumor nor caused death. Our results suggest that urothelial eddy is a rare aberrant histology of papillary urothelial neoplasms with indolent behavior and should be discriminated from squamous differentiation of urothelial carcinoma, which has a poor prognosis.
Department of Pathology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Republic of Korea.
Misung
M
Kim
Jae Y
JY
Ro
Mahul B
MB
Amin
Mariza
M
de Peralta-Venturina
Ghee Young
GY
Kwon
Yong Wook
YW
Park
Yong Mee
YM
Cho
D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis; D002295:Carcinoma, Transitional Cell / Q000378:metabolism / Q000473:pathology*; D018450:Disease Progression; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D046888:Tissue Array Analysis; D001749:Urinary Bladder Neoplasms / Q000378:metabolism / Q000473:pathology*
D014408:Biomarkers, Tumor
Urothelial carcinoma; indolent; urothelial eddy; variant