Middle-aged woman presented at the Emergency Department after minor trauma of the left leg, experiencing pain.
Her past medical history revealed a previous well-differentiated bone lymphoma which was treated with high dose radiotherapy in that leg 30 years before.
On the physical examination a cauliflower-like soft tissue mass was noted (Fig. 1).
Radiographs showed heterogeneously increased bone density and adjacent soft tissue calcifications (Fig.2). In comparison to previous radiographs (taken 9 years before), these findings were overall stable, except for a slight increase in soft tissue calcifications, and were considered radiotherapy-related changes (Fig.3). Additionally, a proximal tibial fracture was suspected and a CT examination was requested.
CT demonstrated similar findings, including a mixed lytic and sclerotic pattern and soft tissue calcifications (Fig.4), and confirmed the presence of a pathologic fracture. Also, ill-defined areas of cortical destruction and amorphous calcifications, less dense than the ones readily seen in the radiographs, were evident.
Since these findings were suspicious in this post-radiation background, MR imaging was performed, showing a destructive infiltrative lesion of the tibia, with an associated soft tissue mass extending to the skin surface. A skip lesion was found in the medial femoral condyle (Fig.5).
A soft tissue biopsy was performed, revealing infiltration by osteosarcoma.
Post-radiation osteosarcoma is a type of secondary osteosarcoma that occurs in the tissues treated with radiation for some other disease process, with an evaluated risk of 0.01-0.03% of all irradiated patients [1]. Moreover, radiation induced osteosarcomas account for about 5.5% of all osteosarcomas [1].
The tumour occurs after a mean latency period of 14.5-15.5 years, with a range of 3-65 years after treatment [2, 3].
Radiation-induced osteosarcomas do not usually occur in heavily damaged areas of bone because these lack the ability to regenerate. Instead, they develop in areas where the dose has been sufficient to cause cell mutation, but not complete sterilization. For this reason, post-radiation osteosarcomas tend to occur in the periphery of the radiation field [3].
To some extent, the improved health care quality has likely contributed to the increase in the life expectancy of these patients, allowing them to live longer and experience the oncogenic effects of radiation therapy.
Malignant osteoid formation with dense sclerosis is a feature of radiation-induced osteosarcoma. Co-existing radiation bone changes are seen in up to 50% of patients. The cardinal features of cortical destruction and soft tissue extension are optimally demonstrated with MR imaging, but CT can also be used [4, 5].
Imaging features of bone healing and remodelling during the process of radiation osteonecrosis are dynamic, and it can be difficult to rule out malignancy. Relative lack of change on serial radiographs favours radiation changes, whereas pain, presence of a soft tissue mass, increasing lytic lesions and active enhancement on imaging favour the diagnosis of recurrent tumour or radiation-associated sarcoma.
Treatment consists of surgery and chemotherapy [6]. Surgical options include wide resection with limb salvage, or wide resection with amputation. The latter option was the one performed in this patient (Fig.6).
Radiation induced osteosarcoma
Based on the provided imaging data (including X-ray, CT, and MRI) as well as clinical photographs, there is a distinct soft tissue mass with a cauliflower-like appearance near the patient’s left knee. X-ray and CT imaging demonstrate:
MRI more clearly shows the soft tissue component of the tumor and its relationship with the surrounding structures. An abnormal signal is observed in the local soft tissue, which is continuous with the bone cortex. Adjacent soft tissue structures also exhibit varying degrees of involvement, with a pronounced soft tissue mass evident.
Clinically, a cauliflower-like mass is visible, accompanied by localized skin breakdown or ulcer-like changes. These findings suggest that the tumor has grown aggressively in the local area.
Considering the patient’s history (previous high-dose radiotherapy for bone lymphoma, a time span of several decades before the new lesion appeared) and imaging characteristics, the following diagnoses are suggested:
Taking into account the patient’s age, symptoms, history of high-dose radiotherapy for bone lymphoma, alongside imaging findings of cortical destruction, soft tissue invasion, and tumor formation/ossification, the most likely diagnosis is:
Radiation-induced Osteosarcoma.
A definitive diagnosis typically requires histopathological confirmation. If a biopsy has not been performed, a pathological biopsy is recommended to confirm the diagnosis.
Rehabilitation focuses on postoperative limb function recovery, prevention of muscle atrophy and joint contractures, and subsequent reconstructive training. If amputation is performed, residual limb care and prosthetic fitting training are key. If limb salvage is performed, restoring joint range of motion and muscle strength is paramount. The following general plan is based on the FITT-VP principle (Frequency, Intensity, Time, Type, Volume, Progression):
Throughout the rehabilitation process, close attention should be paid to incision healing, changes in limb pain, and overall health status. Regular follow-up imaging and relevant lab tests are advised. Seek medical attention promptly if any discomfort or complications arise.
This report is based on the presented images and medical history for reference purposes. It cannot replace an in-person consultation or the professional diagnosis and treatment recommendations of a qualified physician. Specific treatment and rehabilitation plans should be tailored to the individual patient and carried out under the guidance of a professional medical team.
Radiation induced osteosarcoma
