Mesoblastic nephroma (Bolande's tumour) is a rare renal tumour, but, overall, is the most frequent benign renal tumour in childhood and the most frequent renal tumour during the first year of life. It is increasingly diagnosed with US during the fetal period. We report the findings of two patients who showed the "ring" sign, an anechoic ring surrounding the tumour and typical of mesoblastic nephroma. We identified a Doppler signal in the ring in both cases, and pathology confirmed the vascular origin of this sign.

This multicenter collaborative study was undertaken to review the types and complications of femoral neck fractures in children. It is a retrospective clinical and radiological review of 108 femoral neck fractures. Cases originated from four different pediatric hospitals. All the patients had plain radiographs. Fractures occurred at all ages (one day to 18 years), and 63% of the patients were boys. Forty-nine fractures were traumatic; 37 were pathologic, 19 were insufficiency fractures; and three were fatigue fractures. Unless the underlying bone was abnormal, significant high velocity trauma, fall from a height or other severe violence was required to fracture the femoral neck. A unicameral bone cyst was the underlying lesion in 40% of pathologic femoral neck fractures and malignancy in 35%. Osteoporosis as in myelodysplasia, osteogenesis imperfecta and from other causes was responsible for 52% of insufficiency fractures. Because of the unique osseous and vascular anatomy of the femoral head and neck in the growing child, these fractures have a high incidence of complications. Complications included avascular necrosis 13%, premature closure of the epiphyseal plate 12%, varus deformity 8.3%, and nonunion 3.7%. Unless there is a clear history of significant violence, a cause for a femoral neck fracture should be sought, e.g. an underlying bone lesion or a metabolic bone disease. These fractures are rare, but are serious injuries since their complications may lead to a life-long disability.

The authors report the case of a 9-year-old child which suffered from a chondroblastoma of the cervical spine. He had clinical signs of superior mediastinum compression with inflammation of the respiratory upper air-way. Surgery was performed. Diagnosis was established by the pathologist. The recurrence one year later was treated again by surgery and also by radiotherapy. Another recurrence four years later was fatal. The difficulties of the diagnosis and the appearance of recurrences in some cases of chondroblastoma are reviewed in the literature.

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