Paratesticular dedifferentiated liposarcoma with rhabdomyosarcomatous differentiation presenting as hydrocele in an older man: a case report.

Introduction and clinical importance: Most malignant testicular tumors are germ cell tumors (seminomas and non-seminomatous germ cell tumors), which together account for over 90% of primary testicular cancers and predominate in men aged 15-40 years. In contrast, paratesticular sarcomas such as liposarcoma are rare and typically present in older adults. The paratesticular dedifferentiated liposarcoma (PTDDLPS) subtype is exceptionally uncommon variant, and cases showing heterologous rhabdomyosarcomatous differentiation are exceedingly rare, posing diagnostic and therapeutic challenges. Case presentation: We report a case of 83-year-old man presented with a painless, gradually enlarging left scrotal swelling initially suspected to be a hydrocele. Ultrasonography and MRI demonstrated a heterogeneous paratesticular mass. A high inguinal orchidectomy was performed. Histopathological examination revealed dedifferentiated liposarcoma with extensive rhabdomyosarcomatous differentiation. Immunohistochemistry (IHC) showed myoglobin and MyoD1 positivity in the rhabdomyoblastic component, while MDM2 and CDK4 coexpression and molecular analysis in both lipogenic and sarcomatous areas confirmed the diagnosis. The postoperative course was uneventful and the patient was referred for multidisciplinary follow-up. Clinical discussion: PTDDLP with rhabdomyosarcomatous differentiation in the paratesticular region is extremely rare and can mimic other sarcomas or germ-cell tumors. The correct initial surgical treatment is best performed by high inguinal (radical) orchiectomy with early spermatic cord ligation, which is crucial for minimizing scrotal contamination and local recurrence. Recognition of its biphasic morphology, IHC analysis, supported by molecular testing for MDM2 and CDK4 amplification, is essential for accurate classification and management. Conclusion: This case emphasizes the rarity and highlights the importance of clinicopathological features, diagnostic pitfalls, and prognostic implications considering PTDDLPS with rhabdomyosarcomatous differentiation, reinforces the oncologic importance of a high inguinal approach for suspected malignant paratesticular masses in older men. IHC and molecular analyses are crucial for an accurate diagnosis, particularly in tumors with heterologous elements that may mimic other sarcomas or germ cell tumors. Early recognition and multidisciplinary management optimize local control and surveillance planning.