PS-22-008 Impact of total core length for cancer detection in a lateral zone targetted 12-core prostate biopsy scheme U. Berber * , A. Haholu, Z. Kucukodaci, I. Yilmaz, D. Demirel * GATA HEH, Dept. of Pathology, Istanbul, Turkey Conclusion: Total core length is significantly associated with cancer detection rates and may be used as a reliable adjunctive tool in deciding repeat biopsies for patients with negative biopsy result. Objective: Primitive neuroectodermal tumors (PNETs) are highly malignant tumors of neuroectodermal origin. We report a case of renal PNET in a 52-year-old male with a 6-month history of intermittent hematuria.. He underwent a right radical nephrectomy. Macroscopically, the inferior pole was replaced by a multinodular, grey, glistening tumour measuring 8.7/7/6 cm, with foci of necrosis and hemorrhage. Method: Serial histological sections have been assessed using hematoxylin-eosin and Van Gieson stain and the indirect immunohistochemical analysis for antibodies: MNF 116, VIM, CD56, NSE, MIC2/CD99. Results: Histological examination revealed a uniform population of undifferentiated, small-to medium-sized tumor cells, arranged in alveolar-insular patterns, with round to oval nuclei, small nucleoli, numerous signs of mitosis and scattered apoptosis, geographic zones of necrosis. Dispersed cells showed cytoplasmic vimentin positivity favouring the diagnosis of PNET. Few tumoral cells appeared positive for MNF116. Expression of CD56 was positive in a large number of tumoral cells and an area of the tumour exhibit a milder reaction of positive NSE. MIC2 was positive with moderate staining in almost all tumoral cells. Conclusion: Diagnosis is based on histology and immunohistochemistry but pathological evaluation can be challenging because of the differential diagnosis with other small round cell tumors.