Aneurysmal bone cyst primary - about eight pediatric cases: radiological aspects and review of the literature

The aneurysmal bone cyst is a pseudotumoral lesion that can take several aspects. This is a rare lesion representing 1% of bone tumors. It appears usually during the first 30 years of life. The pathogenesis is that of a process of “dysplasia/hyperplasia”, favored by a circulatory deficiency and hemorrhage within the lesion and the phenomena of osteoclasis. The objective of this work is to illustrate with analysis, the specific forms and atypical aneurysmal bone cyst which often pose a diagnostic challenge requiring radiological investigation with histological confirmation. We report eight pediatric cases of aneurysmal cysts collected over a period of 3 years, 3 boys and 5 girls. All patients had standard radiographs. MRI was performed in three patients. The diagnosis was confirmed histologically. The atypia has been in the seat: fibula (1 case), metaphyseal (2 cases), diaphyseal (4 cases) and metatarsal (1 case). Aneurysmal bone cyst is a rare benign tumor with predilection to the metaphysis of long bones. Atypical forms even fewer are dominated by the atypical seat.


Introduction
Aneurysmal bone cysts (ABC) are nonneoplastic expansile lesions that may exist as a primary bone cyst or as a secondary lesion arising from other osseous conditions such as giant cell tumors or unicameral bone cysts [1]. The peak age of occurrence is in the second decade of life; approximately 80% occur within the first two decades.
The long bones (especially the tibia and femur) and vertebrae are the most common sites. However, aneurysmal bone cysts may occur in any bone. The male to female ratio is 1 to 1.3. Pain is the most common clinical symptom at presentation. Local swelling may develop as the lesion increases in size. Occasionally, the patient may present with a pathologic fracture within the aneurismal bone cyst where the cortex is compromised. Major radiographic features include dilated or aneurysmal cystic expansion of the involved bone with no significant matrix mineralization. The lesion tends to affect the metaphyses of long bones and the dorsal elements of the vertebrae. Sclerotic rims with periosteal new bone formation are common. The radiographic differential diagnosis includes unicameral bone cysts, giant cell tumors, osteosarcoma, and osteoblastoma (in vertebral lesions). The diagnosis must be based on histopathologic evidence [2]. Local recurrence rate after classic surgical procedures (curettage and grafting) is about 11.8%-30.8% [3]. The purpose of this article is to show some unusual atypical head of pathology and a review of the literature.

Methods
Patients: From 2008 to 2011, eight patients were treated for ABCs of long and flat bones at Hassan II Hospital by means chirurgical.
The following data were collected retrospectively by one author

Discussion
ABCs represent approximately 1% -2% of all primary bone lesions that are sampled for biopsy [4], with a slight female preponderance, a male-to-female ratio of 1 -1.04 and a median patient age of 13 years in large studies [5,6]. In the present study, the median age was 9.6 years at presentation.
Essadki et al [10] hypothesize that ABCs are caused by the opposed direction of periosteal and medullary blood circulation. ABCs pass through different stages of development as part of their natural progression. The first stage consists of an early osteolytic lesion.
The lesion then progresses into a mature characteristic cyst that eventually evolves into a late or calcified stage. Progression of ABCs is variable. They may have aggressive growth or grow slowly. They eventually mature and rarely undergo spontaneous regression [6,11,12]. Treatment of secondary lesions is directed against the underlying primary lesion [13]. Vergel De Dios et al [14] reported a 20% recurrence rate after curettage with or without bone grafting, usually within the first 2 postoperative years.
A local recurrence rate of 20% after curettage alone was reported by Campanacci et al [15]. The recurrence rate is increased in patients with a mitotic index greater than 7, patients who undergo curettage treatment alone (although repeat curettage usually provides a lasting cure), younger patients (8].

Conclusion
Always think of an aneurysmal bone cyst to a tumor metaphyseal front fan 20. Should always seek a traumatic background and never forget to seek an underlying lesion (secondary ABC).

Competing interests
The authors declare no competing interests.