SUBPERIOSTEAL TIBIAL ANEURYSMAL BONE CYST

Clinical History

A 17-year-old male patient presented, after minimal trauma, with pain in the left lower leg.

Imaging Findings

The patient was presented to our formation with a one month history of progressive pain in the left lower leg after minimal trauma. There was no fever and no weight loss. On physical examination, the patient walked with an antalgic gait, favouring the right side. There was mild pain to direct palpation over the proximal tibial portion. There was no swilling. The flexion, extension and rotation of the leg were no limited. The X-ray of proximal tibial portion revealed a superficial bone defect, with regular margin measuring 2 x 5 cm. This lesion caused an interrupted periosteal reaction with Codman angle. Radiograph image demonstrate an aggressive radiographic appearance (fig 1). MR images showed a multicystic appearance with a hypointense signal on T1-weighted (fig 2), hyperintense signal on T2-weighted (fig 3), without fluid-fluid levels, and contrast-enhancing cyst walls (fig 4). Adjacent soft tissues were normal. Radiographics’ results suggested malignant tumour. Treatment was surgical curettage with bone cementation. The definitive pathologic diagnosis was subperiosteal aneurismal bone cyst.

Discussion

. Aneurismal bone cyst is an uncommon benign tumour, it account for 1% to 2% of all primary bone tumours, and more rare in soft tissue. It’s slow growing expansile lesion usually found in long bones or vertebrae (1). An aneurismal bone cyst is an expansile lesion that contains blood-filled cystic cavities. This lesion can be primary or secondary to an underlying lesion (2). Usually presents in the first 2 decades of life, and exhibits a slight female preponderance. Cytogenetic analysis of aneurismal bone cyst and soft tissue primary aneurismal tumor showed a similar result (3). Radiographs and CT images of subperiostal aneurismal bone cyst showed a superficial bone defect, and can demonstrate an aggressive radiographic appearance (4). CT and MRI are very useful to depict the extent of the lesion and demonstrate the presence of blood-fluid levels, which is a characteristic finding of aneurismal bone cyst (2-5). Septal contrast enhancement proved to be a useful MR imaging finding in aneurismal bone cyst. Magnetic resonance imaging provides improved diagnostic specificity and valuable information on soft tissue changes (3,6). The combined use of conventional radiographs and MRI revealed the highest sensitivity in the diagnosis of aneurysmal bone cyst. But, it’s important to know - That a fluid-fluid level can be observed in wide variety of lesion: osseous and soft tissue masses, neoplastic or nonneoplastic lesions, malignant or benign neoplasms, and primary or metastatic malignancies (osteosarcoma, chondroblastoma and giant cell tumour of bone) (7). - And solid aneurismal bone cyst, a variant of aneurismal bone cyste, has a broader and more variable radiographic appearance. On MR imaging, most lesions were slightly hyperintense to muscle on T1-weighted images and were heterogeneous, with predominantly high signal intensity on T2-weighted sequences. Pronounced edema in the bone and soft tissues adjacent to the lesion was seen (8). Treatment was surgical curettage, with or without adjuvant therapy (phenol or hydrogen peroxide) and bone grafting or cementation. Adjuvant or primary radiation of an aneurismal bone cyst is rarely used because of its association with malignant lesion transformation (9). The prognosis following treatment is very good, although 10% to 20% of cases are reported to recur.

Differential Diagnosis List

Final Diagnosis

Subperiosteal aneurismal bone cyst

URL:	https://www.eurorad.org/case/4983
DOI:	10.1594/EURORAD/CASE.4983
ISSN:	1563-4086