Imaging Findings

1. X-ray and CT demonstrate significant thickening of the right iliac bone and proximal femur, with disordered trabecular patterns and mixed densities, consistent with the known Paget disease lesions in the right pelvis and femur.
2. Focal osteolytic areas are observed, with irregular cortical bone and relatively unclear boundaries.
3. MRI shows abnormal signals in the right proximal femur and pelvic region, with a soft-tissue mass-like lesion, indicating that the disease has extended into extraosseous soft tissue.
4. Overall, imaging findings suggest the possibility of a new or superimposed lesion on the existing Paget disease. Considering the patient’s clinical symptoms (increased right hip pain, prostate issues, etc.), there is a high suspicion of malignant transformation (e.g., sarcoma) or metastatic disease.

Possible Diagnoses

1. Sarcomatous transformation of Paget’s disease: Long-standing Paget’s disease may develop malignant tumors such as osteosarcoma or chondrosarcoma. Radiologically, previously thickened bone may exhibit local osteolytic lesions or soft-tissue masses.

2. Metastatic lesions:

• From previous renal carcinoma: The patient underwent nephrectomy 8 years ago, but late-onset bone metastasis from renal carcinoma can occur, especially in areas affected by Paget’s disease with abundant blood supply.
• Prostate cancer metastasis: The patient presents prostate-related symptoms (“prostatism”). Prostate cancer can metastasize to bone, typically with osteoblastic features, though atypical findings may occur in the context of Paget’s disease.

3. Other rare malignancies: Such as multiple myeloma or lymphoma, which should also be considered in the differential diagnosis. However, based on the patient’s clinical status and history, these are less likely.

Final Diagnosis

Given the suspicious soft-tissue mass and osteolytic changes noted on imaging, along with worsening pain, a high suspicion arises for malignant transformation (sarcoma) or metastatic lesions on the basis of Paget’s disease. The most likely current diagnosis is a metastatic lesion or sarcomatous lesion, pending histopathological biopsy confirmation.

Treatment Plan and Rehabilitation

1. Treatment Strategy

• Biopsy confirmation: Precise imaging-guided biopsy or surgical sampling is required first to determine whether the new lesion is a sarcomatous transformation or metastatic tumor.
• Surgical management: If confirmed malignant, further assessment of tumor extent will guide the feasibility of resection or debulking surgery to control the local lesion, relieve pain, and prevent pathologic fracture.
• Radiotherapy, chemotherapy, or targeted therapy: In cases of metastatic or sarcomatous lesions, consider radiotherapy, chemotherapy, or targeted therapy based on pathology findings. A multidisciplinary treatment plan should be developed with oncology and orthopedic teams.
• Medications: For Paget’s disease, continue or intensify bisphosphonate therapy to mitigate excessive bone remodeling. If bone or tumor-related pain is present, add appropriate analgesics.

2. Rehabilitation / Exercise Prescription
During the diagnostic and treatment phase, the patient should engage in gradual and supervised activity under the guidance of physicians and rehabilitation therapists. Key points include:

• Frequency (F): Depending on the stability of the condition, low-load functional training can be performed 2–3 times per week.
• Intensity (I): Begin with low-intensity exercises, avoiding excessive weight-bearing or high-impact movements, such as bed-based active limb mobilization and range-of-motion exercises.
• Time (T): Start with 10–15 minutes per session, gradually increasing to 20–30 minutes as tolerated, adjusting according to pain levels.
• Type (T): After stabilizing the involved area, consider ambulation training with assistive devices (crutches, walkers), range-of-motion, and muscle-strengthening exercises. Safe passive/active lower-limb rehabilitation equipment can be used for gentle training.
• Volume & Progression (V & P): As tolerance improves and cleared by orthopedic evaluation, gradually advance leg strengthening and stability exercises, but avoid rapid or high-load activities to prevent pathologic fracture.

Throughout rehabilitation, thoroughly assess bone fragility and the risk of pathologic fractures. Exercise under bracing or protective devices if necessary. Closely monitor for joint or muscle pain, and consult a physician or adjust the plan if significant discomfort arises.

[Disclaimer]
This report is based on the provided clinical history and imaging data for reference only, and cannot replace face-to-face consultations or professional medical advice. The final diagnosis and treatment plan should be formulated by specialists from the relevant departments, taking into account the patient’s specific condition.