Solid Variant of Aneurysmal Bone Cyst (SVABC) of the Left Fibula Bone: A Rare Case Report

Abstract

Introduction: Solid variant of aneurysmal bone cyst (SVABC) is a rare subtype of aneurysmal bone cyst (ABC) that presents as a solid, densely sclerotic lesion that can be more difficult to distinguish from other bone tumors and can lead to a wrong diagnosis. The SVABC rarely occurs in the long bones of the lower extremities.

Case presentation: In this report, we present a rare case of SVABC in a 25-year-old male patient, which was seen in the left fibula bone. The patient had a history of trauma for 7 years. A physical examination showed a non-tender swelling in his left fibula bone. A preoperative frontal radiograph showed a huge expansile lytic lesion with trabeculations in the proximal 2/3 of the left fibula. Magnetic Resonance Imaging (MRI) showed fibula with multiple cystic areas in the lesion, some containing fluid-fluid levels. Excision of the mass was performed. Histopathological examination of the surgical specimen of the left fibula mass confirmed that the lesion was SVABC and showed largely solid proliferation of mildly pleomorphic oval to spindle cells with giant cells. A postoperative frontal radiograph of the leg demonstrated proximal 2/3 of the left fibulectomy with no lesion recurrence.

Conclusion: SVABC of the left fibula bone is a rare condition often misdiagnosed due to overlapping features with other aggressive bone lesions. Accurate diagnosis necessitates a multidisciplinary approach integrating clinical, imaging, and histopathology, with early surgical intervention being the gold standard for favorable outcomes. Surgeons must be cautious of postoperative complications like bleeding and neurological deficits, emphasizing the role of histopathology in preventing unnecessary surgeries. Future studies should focus on long-term follow-up and comparative treatment efficacy studies to enhance understanding and management of SVABC.

Keywords: SVABC; bone; excision; osteoclastic giant cells; radiology.

Figure 1

Preoperative frontal radiograph shows a huge expansile lytic lesion with trabeculations in the proximal 2/3 of the left fibula.

Figure 2

Coronal T2 FS MRI shows the lesion expanding the proximal left fibula with multiple cystic areas in the lesion, some containing fluid-fluid levels.

Figure 3

Axial T2 FS MRI shows the lesion expanding the proximal left fibula with multiple cystic areas in the lesion, some containing fluid-fluid levels.

Figure 4

Postoperative frontal radiograph of the leg demonstrates proximal 2/3 of the left fibulectomy.

Figure 5

Grossly, the excisional biopsy shows a white solid mass involving the bone with extensive destruction and extending to the soft tissue. There are areas of cystic change and hemorrhage.

Figure 6

Microscopically, the excisional biopsy shows mostly solid proliferation of mildly pleomorphic oval to spindle cells in fascicles, osteoclast-type giant cells (*), and osteoid matrix lined by osteoblasts, and centrally calcified basophilic material with areas of cystic spaces filled with blood (**), surrounded by multi-nucleated giant cells. *: osteoclast-type giant cells; **: cystic spaces filled with blood. (x40).