Purpose: Intra-osseous leiomyosarcoma (IOLM) is a rare tumour. Imaging aspects are not specific. Pathology is required to establish diagnosis. The appropriate treatment remains controversial because no method has demonstrated certain efficacy. We report two cases and review the literature on this malignant tumour.

Material and methods: The first patient was a 43-year-old woman who suffered right knee pain for six months. Plain x-rays of the tibia revealed an metaphyseo-epiphyseal zone of osteolysis with soft tissue involvement as did 18-FDG uptake on the scintigram and computed tomography. Pathology diagnosis was high-grade IOLM. Search for extension was negative. Tumour resection was performed with implantation of a massive prosthesis followed by chemotherapy and radiotherapy. The second patient was a 50-year-old man who was referred ten days after spontaneous fracture of the lower femur. Plain x-rays, computed tomography and magnetic resonance imagine as well as the PET-scan were difficult to interpret. Pathology examination of a biopsy specimen was in favour of a benign lesion. The final diagnosis was IOLM. Search for extension was negative and radiotherapy was given.

Results: At mean 18-month follow-up, both patients were living. The first patient was able to walk without crutches and the second patient achieved bipodal stance with crutches. Radiologically, the prosthesis was stable and the graft healed. Positive diagnosis was established on the basis of immunohistochemistry and study of the ultrastructure. Unfortunately, treatment of this malignant tumour remains difficult. Chemotherapy and radiotherapy are ineffective. Surgical treatment, even when oncological resection can be achieved, has not demonstrated superior efficacy compared with more conservative treatment in terms of survival or secondary spread. Associating medical and surgical treatment does not guarantee a better result.

Conclusion: IOLM is a rare tumour which requires immunohistochemistry and study of the ultrastructure for positive diagnosis. The appropriate therapeutic option cannot be established, but it would appear that tentatively curative surgery associated with radiotherapy may provide better outcome despite the poor short-term prognosis.

We report a case of an aneurysmal cyst localized in the patella of a 37-year-old man. The lesion was secondary to a chondroblastoma at six years follow-up after initial curettage and bone graft. It were no recurrence. Treatment of aneurysmal cysts depends on the degree of articular involvement. We made a detailed study of 11 cases of this rare localization of aneurysmal cysts reported in the literature.