Osteosarcoma shows a variety of histologic patterns. Uncommonly, this tumour has an epithelioid appearance, and the rosette formation is more rarely observed.

We report an unusual case of a 12 year-old girl who was referred to us with pain and a mass around her left shoulder with upper limb motor dysfunction. X-ray showed a pathologic fracture of the proximal humerus. Biopsy was performed. Histologically, the neoplasm is characterized by a small multinodular growth pattern. The tumoral cells have plasmocitoid or epithelioid shape and they are arranged forming rosettes. Sheet-like osteoid deposition was found. Inmunohistochemical studies revealed the tumour to be positive for epithelial membrane antigen (EMA), vimentine, CD-99 and neuron-specific enolasa (NSE).

The rosette-forming osteosarcoma has an aggressive clinical behaviour. The location, clinical features and chemotherapy effect are important prognostic factors. Histological differential diagnosis includes small cell osteosarcoma, metastatic neuroblastoma, PNET and metastatic carcinoma.

Primary vascular leiomyosarcoma is a rare, aggressively malignant connective tissue tumour, which arises from smooth muscle cells of the vessel walls. This neoplasm involves the extremities in about of 30% reported cases. Preoperative angiograms with CT scans and MRI in conjunction with the clinical signs of vascular and biopsy and immunohistochemical studies are useful tools in the diagnostic and operative planning of intra-vascular leiomyosarcoma.

We report the case of a 34 year-old woman who was referred to us presenting pain, palpable mass in the right inguinal area and tenderness, deep venous thrombosis symptoms and motor dysfunction of her right leg. Biopsy was performed with the diagnosis of Leiomyosarcoma (IIB) of iliac and femoral right veins treated with wide resection and reconstruction of vessels with vascular prosthesis achieving excellent results.

In conclusion, complete surgical resection of the vessel segment is the therapy of choice. Adjuvant therapy, chemotherapy or radiation therapy combined with surgery, is often used for patients with poor prognosis.

Osteosarcoma arising on the periosteal aspect of bone comprises a biologically heterogeneous group of neoplasm. Parosteal osteosarcoma is a low-grade malignant tumour originates at the surface of bone comprising 3–6% of all osteosarcomas and 2% of primary osseous neoplasms. It is most common in young and middle-aged adults and occurs most frequently on the posterior aspect of the distal femur or tibia. The radiologic appearance is often characterized by a large, lobulated, ossific mass in a juxtacortical position. Cortical thickening without aggressive periosteal reaction can be present. Typically the medullary canal is uninvolved. Wide surgical resection and reconstruction is the treatment of choice. The overall prognosis for patients with this lesion depends on the stage of the tumor at presentation. The prognosis for a Parosteal osteosarcoma is generally excellent.

We present an uncommon case of elderly women 70 year-old with a surface osteosarcoma in right femur concomitant with disseminated Breast Carcinoma. The radiological findings showed a juxtacortical mass on the anteromedial aspect of the junction between the mid-third and the distal third of the right femur with areas of new bone formation mimicking Periostal osteosarcoma. We observed a typical Parosteal osteosarcoma when the biopsy was performed. The elected treatment was a wide resection with PTR MUTARS and adjuvant chemotherapy controlling local and systemic diseases.

In conclusion, due to the treatment for the juxtacortical osteosarcomas varies with the diagnosis, an accurate evaluation and appropriate management must be executed to have the best outcomes.