Parosteal osteosarcoma, a relatively rare malignant bone tumor originating from the periosteum [1,2], typically exhibits low metastatic potential and a generally favorable prognosis [3-5]. However, the recurrence of parosteal osteosarcoma, although infrequent, introduces unique complexities in terms of diagnosis, treatment, and management. Local recurrences, often within the same bone, can manifest with more aggressive features than primary tumors, leading to heightened invasion and potential involvement of adjacent tissues, including neural and vascular structures [6]. This can result in compromised blood flow, thrombosis, and the risk of limb ischemia, further complicating the management of such cases. Vascular involvement necessitates meticulous consideration of surgical approaches, including the possible use of grafts for vascular reconstruction and restoration of blood supply.

In this case study, we present a compelling case of recurrent parosteal osteosarcoma in the left distal femur with associated vascular complications. Our comprehensive exploration encompassed the initial patient evaluation, surgical interventions, histopathological insights, and an honest account of the complex challenges in management. By examining this case and comparing our findings with relevant literature, we aimed to provide valuable insights to the understanding of recurrent parosteal osteosarcoma with vascular involvement and provide guidance for effective management strategy.

As per our Institute protocols, IRB approval was waived as it was a retrospective case report. Informed consent was obtained from the subject.

A 21-year-old Indian woman with no prior medical condition or history of radiation exposure presented with swelling and occasional pain in her left distal thigh. Clinical examination revealed an 8×5 cm firm mass on the left distal thigh without any distal neurovascular deficits. Magnetic resonance imaging (MRI) revealed a tumor in the distal femur encasing the popliteal vessels (Fig. 1). Subsequent J-needle biopsy confirmed the diagnosis of parosteal osteosarcoma. Metastatic workup, including high-resolution computed tomography of the thorax and bone scans, was negative for metastasis.

Figure 1. Images of the primary tumor. (A) A 7.0×6.4×8.3 cm lesion with areas of hypo-intensity reflecting calcific areas in the posterior aspect of the distal metaphyseal portion of the left femur, with a para-osseous component suggestive of osteosarcoma. (B) Magnetic resonance imaging revealed the lesion involving adjacent muscles with partial encasement of popliteal vessels. (C) An X-ray image showed an ill-defined sclerotic lesion in the lower end of the femur in the epi-metaphyseal region with soft tissue component and periosteal reaction.

The patient underwent an en bloc transarticular resection of the left distal femur and popliteal vessels. This was followed by modular prosthesis reconstruction of femur, along with autograft reconstruction of the popliteal artery and vein using the saphenous vein. Postoperatively, heparin infusion was initiated at a rate of 1,000 units/hour. However, on the 1st postoperative day, re-exploration was necessary due to arterial thrombus formation. A jump polytetrafluoroethylene (PTFE) graft (6 mm diameter) was placed between the superficial femoral artery and the posterior tibial artery, along with a fasciotomy for compartment syndrome.

Postoperative histopathological examination confirmed a parosteal osteosarcoma (pT1Nx) measuring 7.0×5.5×3.0 cm on the posteromedial aspect of the left distal femur. No invasion of the underlying bone was observed, and the vessel margins were clear. During the recovery period, the patient required regular dressing changes due to the fasciotomy. Broad-spectrum antibiotics were administered, and the wound was later debrided, sutured and covered with a split skin graft. This extended the hospitalization to 28 days. After recovery, the patient regained mobility without assistance, did not report claudication, and had a good range of motion in the knee joint. Also, the posterior tibial artery was palpable. Upon discharge, she was prescribed Warfarin 2 mg and Aspirin 75 mg once daily. Adjuvant therapy is not recommended because of the low-grade nature of parosteal osteosarcomas.

Follow-ups were conducted as per protocol [7], every month for 1 year, every 3 months for the next 2 years, every 6 months for the subsequent 2 years, and annually thereafter. Routine examination was performed using handheld Doppler, and duplex ultrasound (DUS) was performed if the findings were suggestive of graft occlusion. DUS was routinely performed at 1- and 6-month postoperatively. After 6 months, it was performed only if peripheral pulses were absent or if handheld Doppler findings were unsatisfactory. Functional outcomes were calculated using the Musculoskeletal Tumor Society (MSTS) score at the 6-month follow-up [8].

At the 36-month post-surgery assessment, the patient reported no claudication, had an intact pulse, and exhibited no vascular abnormalities on handheld Doppler. Her MSTS score was 27. However, after 41 months of disease-free survival, the patient developed a painless, hard, and immobile mass measuring approximately 3.0×2.5 cm at the site of the previous surgery. No distal vascular compromise was observed, but the patient's MSTS score reduced to 25. Contrast MRI revealed a lobulated calcified soft tissue mass measuring 3.9×3.4×2.3 cm over the medial aspect of the left distal thigh, situated in the intermuscular plane abutting the prosthesis laterally, suggestive of recurrent disease (Fig. 2). Imaging also revealed the absence of flow in both the arterial and venous grafts, which was compensated for by collaterals originating from the superficial femoral vessels. Notably, these collaterals were located far from the site of recurrence. Ultrasound-guided biopsy of the left thigh lesion yielded inconclusive results.

Figure 2. Images of recurrent parosteal osteosarcoma with graft thrombosis. (A) Computed tomography image illustrating lobulated calcified soft tissue attenuation in the medial aspect of the left lower thigh in the intermuscular plane, abutting the prosthesis laterally, suggestive of local recurrence. (B) Axial computed tomography image of the thrombosed graft with good collaterals.

During surgery, the tumor was found to be compressing and eroding the lumen of the PTFE graft, leading to complete obstruction and graft thrombosis. However, the vein graft remained intact but thrombosed, and was retained because no tumor was present. When the superficial femoral artery was clamped proximal to the graft, no compromise was observed in the distal vascularity, as confirmed by a pin-prick test. Wide local excision of the lesion was performed, along with PTFE graft removal (Fig. 3A, B), preserving the collaterals formed proximal to the site of the PTFE graft obstruction. Reconstruction of the arterial and venous grafts was deemed unnecessary. Post-operative histopathology confirmed PTFE graft thrombosis with extraneous compression by the recurrent tumor, which measured 4.5×2.7×2.3 cm without obvious graft wall invasion (Fig. 3C). The microscopic features of the recurrent tumor were consistent with those of parosteal osteosarcoma. The tissue retrieved from within the graft lumen only revealed foreign body giant cells and fibrosis, and it was negative for tumor cells; however, tumor cells were observed surrounding the graft wall (Fig. 4). Despite the absence of vascular reconstruction, the flow in the distal vessels through the collaterals remained intact (Fig. 5). Postoperatively, the patient experienced no claudication symptoms, maintained good range of motion in the left knee without support, displayed intermediate gait and function, and expressed satisfaction with the outcome (MSTS Score, 23).

Figure 3. Intra-operative photograph (A), specimen photograph (B), and grossing image (C) of the en-bloc excision of the recurrent tumor with the polytetrafluoroethylene (PTFE) graft. (A) Arrows indicate the ligated ends of the PTFE graft, which were excised en-bloc with the tumor. (B) Tumor was resected en-bloc with the thrombosed PTFE arterial graft. (C) A gross photograph of the tumor with the PTFE graft cut open, revealing extraluminal compression and graft thrombosis (arrow).

Figure 4. Histopathological examination with hematoxylin and eosin staining under ×10 magnification revealed bony trabeculae lined by osteoblasts and intertrabecular area showing fascicles of spindle cells characterized by a scant amount of cytoplasm, vesicular nuclei, and inconspicuous nucleoli.

Figure 5. Computed tomographic angiography of the affected limb following post en-bloc excision of the recurrent mass with graft. (A) No residual tumor is observed after the en-bloc excision of the recurrent tumor. (B) Angiogram reveals adequate distal collateral supply.

Parosteal osteosarcomas are relatively uncommon, comprising only 4%-6% of all osteosarcomas [8]. They are well-differentiated malignant bone tumors originating from the periosteum with an indolent growth pattern, leading to late invasion of the cortex and limited involvement of the medullary canal [9]. Typically, patients are aged 15-40 years, with a higher incidence during the 3rd decade of life [10]. Additionally, there is a higher predominance among women, with a gender ratio of 1:3.

Patients typically present with a painless lump that persists for several years and is occasionally accompanied by reduced mobility in the adjacent joint [11,12]. Dull discomfort and localized tenderness were the second-most common symptoms. This protracted clinical course distinguishes parosteal osteosarcoma from other conditions in similar locations, such as myositis ossificans and high-grade surface osteosarcoma, which tend to manifest more rapidly and are rarely locally invasive, typically producing a mass effect on neighboring structures [10,13].

Differential diagnoses include benign conditions such as myositis ossificans, periosteal chondroma, synovial chondromatosis, giant cell tumors, non-ossifying fibromas, fibrous dysplasia, enchondromas, and malignant tumors such as extra-skeletal osteosarcoma, chondrosarcoma, high-grade surface osteosarcomas, and metastases. Accurate differentiation relies on a comprehensive assessment combining clinical presentation, radiographic evaluation, and histopathological analysis [14,15].

In cases where these tumors involve the femoral or popliteal vessels, restoring proper vascular function is crucial for preserving limb function. Reconstruction options include the use of synthetic or biological grafts. Biological grafts have been reported to have a lower thrombotic rate [7,16]. In our case, the tumor partially encased the popliteal vessels, and we performed en-bloc resection with popliteal vessels and reconstruction with saphenous vein. However, the bypass graft was occluded; therefore, we performed a PTFE graft bypass for limb salvage. The parosteal osteosarcoma encasing the popliteal vessels is a rare phenomenon, and recurrent parosteal osteosarcoma with vascular involvement is also rare. Despite an extensive literature review, only one case report by Fernández et al. [6] was found detailing a recurrent osteosarcoma of the distal femur engulfing the femoral artery and vein. Surgical intervention entailed wide local excision and the use of an autologous saphenous vein graft for arterial reconstruction between the superficial femoral artery and second portion of popliteal artery without venous reconstruction. Postoperative histopathology confirmed recurrent parosteal osteosarcoma with tumor cells localized in the adventitial layer of the vessel without luminal involvement.

The cause of PTFE graft thrombosis in our case might be a vascular involvement with compression due to recurrent tumor or natural occurrence regarding the poor patency of PTFE graft with distal anastomosis to tibial vessels; nonetheless, this finding may signify tumor dedifferentiation, potentially leading to a more aggressive behavior and an increased risk of metastasis [17]. However, even in instances where the arterial graft is completely occluded, limb salvage is possible because of collateral vessel formation.

In conclusion, vascular involvement should not deter clinicians from considering limb salvage surgery as a viable option for selected patients. Local recurrence can compromise the vasculature by encasing or engulfing vessels, making early detection crucial. Patient symptoms and local findings should be meticulously observed because the diagnosis of recurrence can be challenging owing to imaging artifacts and the presence of a metal prosthesis. Utilizing ultrasound scans and plain radiographs of the affected site offers a cost-effective, readily accessible, non-invasive, and reliable approach for detecting significant abnormalities. Furthermore, the implementation of Metallic Artifact Reducing Software (MARS)-MRI and image-guided biopsy could be a most suitable modality for the precise diagnosis of recurrence.

None.

The authors have nothing to disclose.

Concept and design: AR. Analysis and interpretation: KM, KM, SS. Data collection: GRK. Writing the article: GRK, AR. Critical revision of the article: AR, CKK. Final approval of the article: all authors. Statistical analysis: None. Obtained funding: None. Overall responsibility: AR.