Squamous Cell Carcinoma (scc) Arising from Chronic Pre- Existing Lesions

a. A typical chronic non-healing ulcer with two abnormal findings: roll-out ulcer edge and nodular lesions in scarred tissue, may indicate malignant transformation to either squamous cell carcinoma (SCC) of the skin or osteosarcoma of the bone. b. SCC arising from chronic non-healing osteomyelitis (Marjolin ulcer) is the most likely diagnosis based on the presence of roll-out edge and symptom of pain is probably due to perineural invasion of the tumour (skin nodules). Plain radiographs show chronic OM changes without evidence of tumor osteoid formation. Gross prosection specimen of the excised tissue indicates typical chronic osteomyelitic bone. c. Four-quadrant biopsy or punch biopsies of the ulcer margin for histological examination. A Marjolin ulcer typically lacks basement membrane and should be differentiated from another pre-malignant lesion, squamous pseudoepitheliosis. d. Following a wide resection margin which includes either intercalary segment of the tibia or proximal tibia, normal soft tissue and 6cm normal skin around the ulcer, a large defect is created. By considering a wound bed previously containing an infected tissue and proximity of resection margin to the metaepiphyseal junction, a staged combined reconstruction using a vascularized free flap and megaprosthesis arthroplasty or knee fusion allograft is preferred. If jointpreservation intercalary resection is feasible, a staged procedure consisting of free flap and defect filling with bone cement to initiate the initial stage of membrane-induced osteosynthesis is an option. The bone is stabilized with either circular external fixator or antibiotic-coated locked nail. In the second stage, bone cement is removed through an incised membrane and the defect is reconstructed with either cancellous bone graft or bone graft substitute. This technique is known as membrane-induced osteosynthesis of Masquelae.