Introduction:
Persistent Müllerian duct syndrome (PMDS) is a rare condition in phenotypic and karyotypic males characterized by retained Müllerian structures, such as the uterus and fallopian tubes, and is often associated with cryptorchidism and increased gonadal malignancy risk.

Aim:
To evaluate the risk of contralateral testicular neoplasia in patients with PMDS presenting with primary testicular malignancy and to review the available literature on bilateral gonadal involvement.

Case study:
We report a case of PMDS in a 30-year-old phenotypic and karyotypic male who presented with abdominal pain, weight loss, and a palpable abdominal mass. Imaging showed a large abdominopelvic mass with bilateral cryptorchidism, and surgery revealed an intra-abdominal right testicular tumor associated with Müllerian structures. Histopathology confirmed right testicular seminoma, while the grossly normal contralateral intra-abdominal testis showed focal gonadoblastoma and germ cell neoplasia in situ (GCNIS).

Discussion:
This observation suggests the possibility of occult contralateral gonadal pathology in PMDS, particularly with bilateral cryptorchidism; however, as a single-case finding, it should be interpreted cautiously and not considered definitive evidence of bilateral risk. In our literature review, 63 reported cases of testicular malignancy in PMDS were identified, with bilateral involvement, including malignancy or GCNIS, described in a subset. Although this supports the possibility of contralateral pathology, the evidence is derived from highly selected reports and may be influenced by publication bias.

Conclusions:
This case highlights the need for careful evaluation of both gonads in PMDS and consideration of occult contralateral pathology, while larger collaborative studies are needed to define its true incidence and guide evidence-based management.