(P 62) PROSTHESIS-ASSOCIATED SARCOMA: A REVIEW OF 8 HIGH-GRADE LESIONS ARISING AROUND A TOTAL JOINT ARTHROPLASTY IMPLANT

Objective: Rare instances of sarcoma arising near a metallic implant have been described. We sought to present a cohort of patients who developed high-grade sarcoma around an arthroplasty prosthesis.

Methods: A retrospective record review was conducted for 8 patients who were diagnosed with sarcoma arising around a joint prosthesis. All patients were evaluated at a single institution between 2008 and 2021. Mean age of patients at sarcoma diagnosis was 65 years and 63% of patients were male. The indication for the index joint replacement was osteoarthritis in seven patients and developmental hip dysplasia in a single patient. The mean time from prosthesis implantation to sarcoma diagnosis was 10.7 years (range 4-26).

Results: All sarcomas were discovered around a lower extremity prosthesis. Two tumors were associated with a distal femur TKA prosthesis, three were associated with a proximal femoral THA stem (Figure 1), and three were located within the hip joint of patients with THA prostheses. Four lesions were detected on intraoperative pathology, three were detected on radiographs indicated by joint pain, and one was detected via surveillance PET-CT for melanoma.
All lesions were high-grade. Seven of eight tumors had a soft tissue component in addition to osseous involvement. Histologically, 4 tumors were undifferentiated pleomorphic sarcomas, composed of markedly pleomorphic spindled cells with brisk mitotic activity and foci of necrosis; immunohistochemical studies showed a purely fibroblastic phenotype. Two angiosarcomas were seen, one of which showed predominantly epithelioid morphology and was originally confused with metastatic carcinoma. Both cases showed formation of irregular vascular channels by highly malignant-appearing endothelial cells with prominent nucleoli and easily identified mitotic figures. Markers of endothelial differentiation (e.g., CD31, ERG protein, FLI1 protein) were positive. The last two cases showed formation of osteocartilaginous matrix by pleomorphic spindled and epithelioid cells and were classified as osteosarcomas.
Four patients had developed metastatic disease (lung [n=3] and scapula [n=1] prior to treatment. Six patients underwent surgical resection in the form of limb salvage (n=3) or amputation (n=3). Five patients were treated with chemotherapy and two patients received radiotherapy. One patient developed local recurrence 10 months following limb salvage. Another patient developed lung metastases 10 months following hip disarticulation. Four patients died of disease at a mean 8.3 months (range-2-14) from diagnosis. The remaining four patients were alive at final follow-up (mean survival 28 months, range 15-57).

Conclusion: Sarcoma arising around an arthroplasty prosthesis is a rare entity and occurs years after implantation. In our series, these were most commonly discovered incidentally on intraoperative pathology or via surveillance imaging and all were high-grade lesions. Fifty-percent of patients presented with metastatic disease or developed metastases prior to initiation of treatment. Outcomes in this population are poor with half of patients succumbing to disease within 14 months.