Case report: Two sisters with a germline CHEK2 variant and distinct endocrine neoplasias

Checkpoint Kinase 2 (CHEK2) Gene Mutation in a Patient With Breast and Prostate Cancer: A Unique Presentation of a Rare Disease

Breast cancer is one of the rarest malignancies in males, with a low incidence rate compared to all breast cancers. Gene mutation plays a significant role in the pathologic process of cancer. Mutations in breast cancer gene 1 (BRCA1) and breast cancer gene 2 (BRCA2) have been associated with male breast cancer (MBC), as well as prostate cancer (PCa). Despite the etiopathogenetic similarity, combined MBC and PCa is a rare entity. This report presents the case of a 57-year-old male with a history of breast cancer who underwent modified radical mastectomy (MRM) with lymph node dissection followed by adjuvant chemoradiotherapy four years ago. The patient presented with recurrent episodes of voiding dysfunction for three months, followed by urine retention. His family history was positive for breast and lung cancer. High prostate-specific antigen (PSA) and Prostate Imaging-Reporting and Data System 5 (PI-RADS5) necessitate transrectal ultrasound-guided biopsy, which confirmed the diagnosis of PCa. Molecular genetics testing and next-generation sequencing (NGS) analysis identified heterozygous variant c.636T>G, p.(Tyr212*) in the checkpoint kinase 2 (CHEK2) gene. The patient is planned for neoadjuvant luteinizing hormone-releasing hormone (LHRH) for 3-6 months, to be followed by transurethral tunneling of the prostate (TUTP) with adjuvant LHRH. The allele frequency of this patient mutation was documented for the first time among the general population, and it has not been described in the literature. This unique and rare case was presented with clinical, morphological, and immunohistochemical features together with a review of the current literature.