Whole-exome sequencing for high-risk primary prostatic extra-gastrointestinal stromal tumor: A case report

The low incidence rates of prostatic extra-gastrointestinal stromal tumors (EGIST), combined with the lack of published guidelines on its treatment, often results in its misdiagnosis and challenges in the treatment of patients, even in cases with high-risk factors. The present case study reported a 65-years-old Chinese male patient, who presented with intermittent hematuria and lower urinary tract symptoms for three months. The colonoscopy results revealed no gastrointestinal lesions; however, a core biopsy diagnosed an EGIST, which subsequently underwent radical prostatocystotomy, standard pelvic lymph node resection, and bricker ileal conduit diversion. The postoperative pathological results suggested a high-risk primary prostatic EGIST, according to the aggressive behavior of the GIST. The immunohistochemistry results revealed the positive expression of CD117, DOG1, CD34, androgen receptor AR, prostate-specific antigen (PSA), a 2% Ki-67 index and a positive surgical margin. The whole exome sequencing (WES) results revealed that the patient harbored a single nucleotide mutation in 121 genes and copy number variations in 601 genes, including a defect in c-Kit (in-frame deletion in p.Q556-V560; fold, 17.5%). By compiling the data obtained from the ConsensusPathDB and the drug-gene interaction databases and expert opinions, the patient was prescribed with the personalized drugs (400 mg per day imatinib mesylate and 50 mg per day bicalutamide, which were stopped when the PSA levels remained stable below 0.01 ng/ml) for 18 months follow-up and there were no signs of recurrence. In conclusion, WES identified multiple genomic alterations and the underlying genetic defect in the rare case enabled the evaluation of the prognosis and the decision of potential drug candidates. The underlying mechanism of the substantial genetic variations in the primary prostatic EGIST, as well as the malignant behaviors of the tumor, remain to be investigated.