Aim: Urothelial (transitional cell) tumors account for about 90% of all bladder tumors. Their presentation varies from benign lesions that rarely recur to highly malignant tumors. Inverted (endophytic) growth pattern in urothelial carcinoma is particulary hard to distinguish from inverted papilloma. Morphologic criteria alone are not enough and immunohistochemical assesments must also be done, especially in cases of small size biopsy material or transurethral resections. The aim of this study was to accentuate the importance and ways of differentiation of this variable forms as their treatment and prognosis differ.
Patients and methods: In the period from 01.01.2008. to 30.06.2009. at Department of Pathology, University Hospital "Sestre milosrdnice" four patients were diagnosed with low-grade urothelial carcinoma with an inverted growth pattern. Routine histology and additional immunohistochemistry to p53, Ki-67 and CK 7 and 20 was performed.
Results: There were three male patients aging 37, 61 and 69 years and one female aged 46 (mean 53.3 years). Three patients presented with painless hematuria while the last patient had microhaematuria as an Incidental finding. Histologically, tumors formed nests of atypical urothelial cells. Very few or no mitotic figures were observed. Invasion of lamina propria was present in three specimens. Immunohistochemically, positive staining to p53 and CK 20 was observed in all four cases and staining to CK 7 in two. Staining to CK 20 was positive in 80%-100% of tumor cells while the number of p53 positive cells was between 20% and 40% in all four cases. Proliferative activity was assesed using Ki-67 antibody. The percentage of positively stained tumor cells, assesed in hot spots under high magnification (400x), was 5%, 7%, 8% and 12% (mean 8%).
Conclusion: Urothelial carcinoma with inverted growth pattern and inverted papilloma have similar morphologic features but their biological behaviour, treatment and prognosis are different. In order to avoid the urothelial carcinoma to be misdiagnosed as a benign papilloma, we find it very important to make additional investigations beside conventional histology. Immunohistochemical staining for CK 20, p53 and Ki-67, which is positive in most carcinomas, can help us make the right diagnosis.