Pelvic Osteosarcoma with Atypical Presentation in an Elderly Patient

Abstract

Introduction: Osteosarcoma of the iliac bone is a rare malignant bone neoplasm, particularly in older adults. Its clinical presentation can be misleading, often mimicking benign conditions, especially in the context of previous trauma. Timely diagnosis is challenging due to the nonspecific nature of early symptoms and the deep anatomical location of the tumor.

Case presentation: A 63-year-old male with no relevant medical history presented to the emergency department with chronic progressive right lumbar pain, localized swelling, and impaired ambulation, following a reported traumatic event eight months prior. Physical examination revealed a large, stony mass in the right gluteal and lumbar region, with chronic inflammatory signs and massive edema of the ipsilateral lower limb. Initial imaging with ultrasound suggested an organized hematoma; however, due to persistent symptoms, a non-contrast-enhanced CT scan was performed, revealing an expansive soft-tissue lesion with bony erosion of the sacral ala and right iliac bone, suggestive of a neoplastic process. The initial surgical approach was suspended in favor of image-guided percutaneous drainage and biopsy. Histopathology confirmed a high-grade bone sarcoma consistent with osteosarcoma. Staging included whole-body bone scintigraphy, chest CT, and contrast-enhanced pelvic MRI. A multidisciplinary team decided on neoadjuvant chemotherapy followed by surgical planning. At six weeks of follow-up, no evidence of metastatic disease was found, and the patient remained functionally stable.

Conclusions: Iliac wing osteosarcoma may present insidiously and resemble benign post-traumatic lesions. This case underscores the importance of thorough clinical and imaging evaluation and a multidisciplinary approach in patients with slow-growing masses, persistent pain, and atypical fractures, particularly in the elderly population.

Keywords: pelvic osteosarcoma; pathological fracture; post-traumatic mass; bone sarcoma; computed tomography; differential diagnosis.