We describe a case of a patient who presented with pain of the right knee and underwent MR, RX and then scintigraphy and CT; the imaging features suggested a diagnosis of bone metastasis from RCC.
A 61-year-old male presented with pain of the right knee from 2 months. Past history: left nephrectomy 2 years ago for renal cell carcinoma (pT2). The patient was affected by poliomyelitis. MR performed on the patient revealed the presence of a tumour in the distal femur and described it as malignant looking. The patient underwent an extemporary radiography and then a bone scintigraphy and CT of the chest and of the abdomen. Imaging demonstrated a local recurrence at the nephrectomy site, contralateral adrenal gland, pulmonary and mediastinal lymph node metastases.
The overall incidence of metastatic disease following RCC surgery is approximately 40%, the risk being related mostly to high tumour stage and grade. Eighty-five percent of these recurrences occur within 3 years after initial resection but have reported up to several decades later. Risk of relapse is stage-dependent, with a higher rate of metastases in patients with pT3 and pT4 renal tumours compared with lower stages. Also higher tumour grades are more likely to develop metastases and tumour nuclear grading of RCC is a predictor of survival; one study showed 5-year survival rates of 89%, 65% and 45% for grades 1,2, and 3-4, respectively. Histologic subtype of the primary RCC also predicts the development of metastatic disease. Many studies have shown a trend towards a better prognosis for patients with cromophobe, papillary, and conventional (clear cell) RCCs, respectively. Metastatic lesions from kidney cancer are seen in virtually ever organ: lung (50-60%); bone (30-40% ); liver (30-40%); and adrenal gland, contralateral kidney, retroperitoneum, and brain (5% each). The prognosis for RCC with metastasis is poor, with fewer than 9% of patients surviving at 5 years. The whole body of literature on follow-up after surgical treatment of RCC is based on observational studies with a lack of randomized trials. Clinical assessment including history recording, physical examination, and laboratory studies, as well as chest x-ray, should be performed twice a year for the first 3 yr and then annually, irrespective of the tumour pathologic stage. Abdominal CT scan may not be recommended for pathologic stages T1 and T2, while most studies support scanning to be performed every 6 mo for the first 2-3 yr and then every 2-3 yr for patients with pT3 tumours. Metastases to bone are 25 times more common than primary skeletal neoplasms. We have not found MR criteria that reliably differentiate between metastatic and primary disease. The differential diagnoses are multiple myeloma, lymphoma, paget disease, hemangioma and malignant fibrous histiocytoma (MFH). Thus, whenever a focal mass is seen on MR, close evaluation for multiple lesions and correlation with patient history is important. Using T1-weighted and STIR sequences, MRI has been shown to be more sensitive and specific than bone scintigraphy. On T1-weighted images, focal or diffuse areas of hypointensity are shown; on STIR images, lesions appear hyperintense. Whereas MR is the imaging technique of choice for detecting the presence and determining the local extent of disease, the nuclear medicine bone scan continues to be essential in many clinical situations because of its ability to survey the entire skeleton. Bone metastases classically appear as large expansile lytic lesions on plain radiography. Contrast-enhanced CT shows bone destruction with or without the presence of an enhancing soft-tissue mass.
bone metastasis from renal cell carcinoma (RCC)
1. X-ray: On the anteroposterior and lateral views of the right knee joint, the distal femur shows bone destruction with a lytic pattern. The lesion boundaries are not clearly defined; there is a mild expansile change, and no obvious periosteal thickening or reactive sclerosis is seen in the surrounding area.
2. Magnetic Resonance Imaging (MRI): On T1-weighted images, the distal femoral lesion has decreased signal intensity (low signal). On STIR or T2-weighted images, the lesion displays high signal intensity, indicating an active process. There are soft tissue involvement signs, and the interface between the lesion and surrounding bone marrow space is poorly demarcated, suggesting a possible space-occupying or metastatic lesion.
3. Computed Tomography (CT): The bony destruction is more clearly visualized, showing an expansile lytic lesion in the distal femur. Part of the area suggests a soft tissue mass with possible hypervascularity. Combined with abdominal and chest CT findings, there is evidence of prior surgical/treatment changes in the kidney and lungs, consistent with a history of renal cell carcinoma (RCC).
4. Overall presentation: An irregular lytic lesion is located in the distal femur near the right knee joint. Taking into account the patient’s history of renal carcinoma and current symptoms, there are strong indications of distant bone metastasis.
Based on the imaging findings and the patient’s history of renal cell carcinoma (RCC), the following possibilities are considered:
1. Renal Cell Carcinoma Bone Metastasis: RCC commonly presents with lytic lesions, and distant metastases can occur years after surgery. Radiologically, it may exhibit expansile osteolytic changes without a clear sclerotic margin, in line with this case.
2. Multiple Myeloma: Typically appears as multiple lytic lesions with abnormal bone marrow signals. Clinically, myeloma often presents with abnormal serum protein electrophoresis, anemia, or renal dysfunction. Given the patient’s known primary malignancy (RCC), myeloma is less likely as the top differential.
3. Lymphoma Involving Bone: Could manifest as focal or diffuse bone destruction. However, in light of the patient’s renal carcinoma history, this is a lower priority consideration.
4. Paget’s Disease: Commonly features bony enlargement, overgrowth, and deformities. Purely lytic or localized destructive lesions are less characteristic; thus, it is unlikely.
5. Other Primary Bone Tumors (e.g., Malignant Fibrous Histiocytoma): These may also show lytic bone destruction on imaging but lack distinctive features. Given the background of renal carcinoma, metastatic disease is still the most probable.
Considering that:
1. Treatment Strategy Overview:
- Surgical Treatment: In cases of a solitary or localized metastatic lesion, surgical approaches such as cement augmentation, curettage, internal fixation, or segmental resection may be considered to alleviate pain and stabilize the joint structure.
- Radiation Therapy: For patients ineligible for surgery or those with multiple widespread metastatic lesions, local or whole-bone radiotherapy can help relieve pain and prevent further skeletal complications.
- Systemic Therapy: This may include targeted therapies (e.g., tyrosine kinase inhibitors) and/or immunotherapies, as well as bisphosphonates or osteoclast-inhibiting agents (e.g., denosumab) to control bone destruction and reduce pain.
- Palliative Treatment: In advanced disease or when the general condition is poor, the focus should be on pain management, quality of life, and comprehensive supportive care.
2. Rehabilitation/Exercise Prescription Suggestions:
- General Principle: Gradually restore joint mobility and muscle strength while ensuring bone stability and safety. Tailor exercise types and intensity to the patient’s overall status, avoiding excessive weight-bearing or high-impact activities.
- Initial Phase (post-surgery or when pain is significant):
Disclaimer: This report provides a preliminary analysis based on existing imaging findings and medical history. It should not replace an in-person evaluation or a professional physician’s advice. The specific treatment plan must be determined by specialty doctors after a comprehensive assessment of the patient’s condition.
bone metastasis from renal cell carcinoma (RCC)
