A rare Ewing-like small round cell tumor in prostate: a case report and literature review.

BACKGROUND: Small round cell tumor (SRCT) is a group of malignancy with similar optical microscopic morphology. Despite its low incidence, SRCT has a high malignant degree and poor prognosis. Besides, atypical clinical symptoms make it difficult in preoperative diagnosis.

CASE REPORT: A 67-year-old man was presented to the outpatient service with dysuria and weak urine stream lasting for 3 months. After oral treatment with tamsulosin and finasteride for 2 months, the symptoms worsen. Transurethral prostate holmium laser enucleation was operated and postoperative pathology result revealed small blue round cell malignant tumor. Further immunohistochemistry and fluorescence in situ hybridization examination indicated Ewing-like SRCT. So a Da Vinci Robotic prostatectomy was performed further and whole-genome sequencing was conducted. Several gene mutations including RAF1, ARID1A, SMARCA4, and BCL2L11 were found but no FDA-approved drug could treat specifically. Then the patient received Ewing-type therapeutic regimens treatment and has been followed up to date (over 24 months).

CONCLUSION: Because of its non-elevated serum PSA level, prostate SRCT is often ignored as a possibility of malignant tumor and regarded as benign prostatic hyperplasia (BPH). The possibility of prostate SRCT need to be considered if dysuria symptoms could not alleviate significantly after a period of oral treatment.