Case of MYB-Rearranged Prostatic Adenoid Cystic Carcinoma

Background: Prostatic adenoid cystic carcinoma/basal cell carcinoma (ACC/BCC) has been reclassified under the fifth edition of the World Health Organization's classification of tumors, distinguishing it from basal cell cancer of the skin. This malignant neoplasm exhibits distinct biological characteristics that differ from those of typical prostatic adenocarcinoma. However, optimal clinical management of prostatic ACC/BCC remains uncertain because of its rarity and the limited evidence available. Methods: This study retrospectively reviews the treatment course of a 62-year-old male patient presenting with more than six months of dysuria. Initial management included transurethral plasmakinetic resection of the prostate (TUPKP), followed by robot-assisted radical prostatectomy and bilateral pelvic lymph node dissection. Postoperative fluorescence in situ hybridization (FISH) demonstrated MYB rearrangement, providing molecular support for the pathological classification of prostatic ACC/BCC and facilitating diagnostic reclassification. Results: Pathological examination of the TUPKP specimen indicated poorly differentiated carcinoma, with findings consistent with prostatic ACC/BCC. Preoperative imaging showed an irregular soft-tissue lesion in the prostate/bladder neck region, without definite pelvic lymph node or distant organ metastasis. Histological analysis demonstrated cribriform structures and perineural invasion, while immunohistochemistry supported a basal cell phenotype; together with these findings, detection of MYB rearrangement via FISH supported reclassification of the tumor as prostatic ACC/BCC. Following radical surgery, adjuvant paclitaxel plus carboplatin was administered as an individualized empirical treatment in the absence of an established disease-specific standard. The patient completed six cycles of adjuvant chemotherapy and remained clinically stable during follow-up, with no radiological evidence of recurrence at the latest evaluation. Conclusions: This case highlights the diagnostic challenges of prostatic ACC/BCC and underscores the value of integrating molecular findings with histopathological and immunohistochemical features to support accurate tumor classification and individualized clinical management. MYB rearrangement may provide useful molecular support for diagnosis and classification; however, its biological and potential therapeutic significance in prostatic ACC/BCC requires further investigation in larger cohorts.