Variant Of Aneurysmal Bone Cyst Research Articles

Pathologic evaluation of the solid variant of aneurysmal bone cysts with USP6 rearrangement with an emphasis on the frequent diagnostic pitfalls.

The solid variant of aneurysmal bone cyst (SVABC) is very uncommon and frequently misdiagnosed. We reevaluated and summarized the clinicopathologic features of 17 SVABCs and further discussed the use of this nomenclature to differ SVABCs from extragnathic giant cell reparative granuloma (GCRG) in the setting of the USP6 rearrangement era. The immunohistochemical markers included α-SMA, SATB2, AE1/AE3, Ki67, S100, CD68 and P63. USP-6 status was detected by fluorescence in situ hybridization using a break-apart probe. The 17 patients with SVABCs comprised 10 males and 7 females ranging in age from 4 to 70 years. The involved locations included the long bone (n = 11), hand (n = 4), rib (n = 1) and vertebra (n = 1). The lesions were characterized by proliferated spindle cells with scattered giant cells and hemorrhages with variable positive α-SMA, SATB2, CD68 and Ki-67 expression. All patients had USP6 rearrangements without H3F3A glycine 34 mutations. Our study reveals that SVABC shares similar clinical and histologic features with other bone lesions, which may lead to an erroneous diagnosis. The presence of an USP-6 rearrangement contributes to the diagnosis SVABC; SVABC and most of the previously documented extragnathic GCRGs may be considered within the umbrella of primary aneurysmal bone cysts.

Solid variant ABC of long tubular bones: A diagnostic conundrum for the radiologist.

Solid variant of aneurysmal bone cyst (sABC) is an extremely rare, reactive and non-neoplastic osseous lesion. On imaging it presents as a diaphyseal aggressive, eccentrically placed lytic and expansile lesion. However, differentiating this entity from the other possible malignant differentials is confounded by the histopathology mimicking several commoner lesions. We describe the distinctive MRI features of sABC of long bones from a series of four cases and briefly review the literature. We hope this review will educate all radiologists about this rare entity increasing their diagnostic confidence while formulating differentials for similar appearing lesions.

Monostotic Fibrous Dysplasia of the Lumbar Spine With Secondary Features of Solid Variant Aneurysmal Bone Cyst.

Fibrous dysplasia is a benign, mass-forming disease of bone composed of abnormal fibrous and osseous elements that can be accompanied by endocrine dysfunction, skin pigmentation, and intramuscular myxomas. It is usually encountered as a solitary lesion in the tibia or femur but can develop in any bone and can be unifocal or multifocal. Difficulty arises when a solitary lesion is identified in an uncommon site or when there are prominent secondary changes, such as aneurysmal bone cyst (ABC). Molecular studies are available as an adjunct to histomorphology to aid distinction from other entities. GNAS mutations, present in greater than 70% of fibrous dysplasia cases, help in the distinction from primary ABC and low-grade osteosarcoma, which exhibit different molecular abnormalities. We report a case of monostotic fibrous dysplasia in a lumbar vertebral body with secondary change consisting of the solid variant of ABC.

Solid Variant of Aneurysmal Bone Cyst of the Temporal Bone

Aneurysmal bone cysts (ABC) are benign, rapidly growing osteolytic lesions. Solid variant of ABC (SVABC) is a rare subtype of ABC that has not been reported in the temporal bone. We report the case of a 6-year-old boy presenting with a slowly enlarging bony protuberance over the right zygomatic/malar eminence region. Computed tomography and magnetic resonance imaging demonstrated a 2.6 × 5.8 × 5.1 cm temporal bone mass involving the right mastoid, petrous, and temporal squamosal calvarium, with extradural intracranial extension to the middle cranial fossa. The patient underwent preoperative embolization of feeder arteries followed by combined neurosurgical and neurotologic resection. Histopathology revealed characteristic ABC features with interspersed areas of intralesional osteoid formation. Solid variant of ABCs are rare lesions of the skull base that present a diagnostic challenge given their unique radiographic and histologic features. Thorough cytogenetic evaluation is warranted to rule out potential malignant secondary causes. Early surgical resection is essential due to the risk of intracranial extension. This is the first report of ABC of any type with concurrent involvement of the squamous, mastoid, and petrous portions of the temporal bone and the first report of SVABC of the temporal bone.

Large Predominantly Solid Variant of Aneurysmal Bone Cyst in the Diaphysis of Femur: A Rare Entity

Although predominantly metaphyseal, ABC can sometimes also occur purely in the diaphyseal location and may have solid appearance on MRI and therefore must always be considered a differential diagnosis whenever a diaphyseal predominantly solid lesion in long tubular bone is seen in young individuals.

Clinical character and surgical interventions of solid variant of aneurysmal bone cyst in the iliac bone

Objective To retrospectively study the character and surgical interventions of solid variant of aneurysmal bone cyst in the iliac bone. Methods All the clinical data of 6 cases of solid variant of aneurysmal bone cyst arising in the iliac bone which underwent surgical treatment in our department from January 2002 to March 2014 were retrospectively analyzed, including 5 males and 1 female. The patients ranged from 21 to 66 years old at diagnosis, with an average age of 44.0 years old. 1 patient underwent massive resection of the iliac bone, while other 5 patients underwent intralesional treatment. 2 patients underwent allograft and 1 patient underwent bone cement reconstruction, with titanium rod to strengthen pelvic ring and acetabulum. 1 patient underwent packing with osseous granula on the top of the acetabulum and bone cement. 1 patient underwent bone cement reconstruction with Steinmann Pin and occurred diffused wound bleeding then local radiotherapy was given. Results The average age of patients was 44.0 years, which was older than those who had common aneurysmal bone cyst or giant cell tumor. X-ray of the pelvis revealed an expansile, lytic lesion located centrally with partially-sclerotic margins, and a pelvic CT confirmed the plain radiographic findings more obviously. MRI of the pelvis revealed that the expansile iliac bone lesion was equal intensity on T1WI. T2WI and post-contrast images showed heterogeneous signal and enhancement. The signal of soft tissue edema nearby the tumor margin could be found in 3 cases. The operative time ranged from 80 to 240 min (mean, 110 min). The intraoperative boold loss ranged from 300 to 1 600 ml (mean, 900 ml). The followup period ranged from 3 to 141 months (mean, 41.1 months). There were no local recurrence and loosen of internal implants in all patients. Conclusion Solid variant of aneurysmal bone cyst are rarely seen in the iliac bone and the early clinical manifestation is atypical, which is due to a reactive vascular process of native bone. So we conclude intralesional treatment with allograft or bone cement reconstruction is a reliable option for solid variant of aneurysmal bone cyst in the iliac bone. Local radiotherapy with small dose is also reliable option for the patients who have diffused wound bleeding after operation. Key words: Ilium; Bone cysts, aneurysmal; Treatment outcome; Radiotherapy

Solid variant of aneurysmal bone cyst presenting as a giant cervical mass: A clinical, radiological, histopathological dilemma

Background:Typical aneurysmal bone cysts (ABCs) are osteolytic, multicystic lesions with parietal sclerosis and blood-filled cysts. In rare instances, the cystic components may be completely absent. Such solid variants in ABC (s-ABC) exhibit a solid architecture; making the clinical, radiological, and histological differentiation from other solid bone tumors like osteosarcoma (especially giant cell rich osteosarcoma) and giant cell tumor, a difficult task.Case Report:We report the case of a 45–year-old male presenting with a giant solid cervical spine lesion. Histopathology revealed solid variant of ABC, even though the radiological and fine needle aspiration cytology studies pointed toward a giant cell tumor.Conclusion:We aim to discuss the clinical, radiological, and histological findings of solid ABC (a rare benign entity) vis-à-vis the common neoplastic entities of osteosarcoma and giant cell tumor. The histopathological nuisances in making the diagnosis of s-ABC are put forth, along with its impact on management of such giant bony spinal lesions.

Lateral leg pain

AP radiograph demonstrates a well-defined, expansile, lytic lesion of the proximal fibula with marginal sclerosis, while MRI demonstrates a solid, enhancing lesion with a single small focus of cystic signal abnormality. Histopathology demonstrates multinucleated giant cells seen in a background of spindle cells. The solid variant of aneurysmal bone cyst (S-ABC) is a rare entity, constituting 5–7.5 % of all ABCs [1, 2]. The term S-ABC was first introduced by Sanerkin et al. in 1983, when the authors described solid lesions with the same histological features seen in the walls of ABCs [3]. LikeABC, S-ABCwas previously considered a non-neoplastic, reactive lesion, but recent studies have shown that pathogenesis may relate to cytogenetic abnormalities, specifically chromosomal translocations involving the USP6 gene [4–6]. The mean age at presentation of S-ABC is typically in the second or third decade, and is slightly more prevalent in females. Pain, swelling, and/or palpable mass are common presenting symptoms. S-ABC of the spine can produce radiculopathy. S-ABC tends to occur in the face and spine, femur and tibia, and short tubular bones of the hands and feet [1, 2, 5, 7]. When occurring in the mandible, maxilla, hands, or feet, S-ABC may be referred to as “giant cell reparative granuloma” [4, 5, 7]. Similar to ABC, S-ABC typically presents on radiographs as a geographic, lucent, expansile lesion with endosteal scalloping or cortical thinning without matrix mineralization. S-ABC demonstrates a narrow zone of transition with marginal sclerosis, which may be complete in more than half of cases [1, 2, 4, 7, 8]. In long bones, S-ABC is often eccentric and most commonly involves the metaphysis. In the spine, SABC typically occurs in the posterior elements. At MRI, S-ABC demonstrates homogenous decreased signal on T1-weighted sequences without internal hemorrhage. On T2-weighted imaging, S-ABC appears mostly solid with moderately increased signal and scattered cystic areas of fluid signal [7–9]. However, in contrast to ABC, these cystic areas are less common and do not demonstrate septations or fluidfluid levels typical of ABC [7, 9]. Following contrast administration, S-ABC demonstrates diffuse uniform enhancement, rather than peripheral/septal enhancement commonly seen with ABC [7–9]. The differential diagnosis for S-ABC may include ABC, giant cell tumor, chondroblastoma, and telangiectatic osteosarcoma [5, 7, 8].While S-ABCmay be difficult to distinguish from ABC clinically or radiographically, there are characteristic differences on MRI discussed above. GCT occurs in slightly older patients, most often involves the epiphysis, and less commonly demonstrates marginal sclerosis. Chondroblastoma demonstrates chondroid mineralization and signal intensity, involves the epiphysis, and usually incites marked inflammation. Telangiectatic osteosarcoma often has a wide zone of transition with cortical disruption, aggressive periosteal reaction, and soft tissue mass. Due to symptoms and potential for growth, S-ABC is often treated with curettage and bone grafting, as in this patient The case presentation can be found at doi: 10.1007/s00256-014-2049-5

USP6 gene rearrangements occur preferentially in giant cell reparative granulomas of the hands and feet but not in gnathic location.

Giant cell reparative granulomas (GCRGs) are lytic lesions that occur predominantly in the gnathic bones and occasionally in the small bones of the hands and feet. They are morphologically indistinguishable from, and are regarded as synonymous with, solid variant of aneurysmal bone cysts (ABC) in extragnathic sites. Identification of USP6 gene rearrangements in primary ABC has made possible investigating potential pathogenetic relationships with other morphologic mimics. USP6 gene alterations in giant cell-rich lesions (GCRG/ABC) of small bones of the hands and feet have not been previously studied. We investigated USP6 gene alterations in a group of 9 giant cell-rich lesions of the hands and feet and compared the findings with morphologically similar lesions including 8 gnathic GCRGs, 22 primary ABCs, 8 giant cell tumors of bone, and 2 brown tumors of hyperparathyroidism. Overall, there were 49 samples from 48 patients including 26 females and 22 males. Of the 9 lesions of the hands and feet, 8 (89%) showed USP6 gene rearrangements, whereas no abnormalities were identified in the 8 gnathic GCRGs, 2 brown tumors, or 8 giant cell tumors of bone. Of the 22 primary ABCs, 13 (59%) showed USP6 gene rearrangements. In conclusion, most GCRGs of the hands and feet represent true ABCs and should be classified as such. The terminology of GCRG should be limited to lesions from gnathic location. Fluorescence in situ hybridization for USP6 break-apart is a useful ancillary tool in the diagnosis of primary ABCs and distinguishing them from GCRGs and other morphologically similar lesions.

Solid variant of aneurysmal bone cyst in the acetabulum

Solid variant of aneurysmal bone cyst in the acetabulum

Expert’s comment concerning Grand Rounds case entitled “Solid variant of aneurysmal bone cyst on the cervical spine of a child: case report, differential diagnosis, and treatment rationale” (by Christos Karampalis, Robert Lenthall, and Bronek Boszczyk)

This article reports a case of solid variant aneurysmal bone cyst (S-ABC) in the cervical spine of a child [1]. Aneurysmal bone cyst (ABC) of the vertebral column occurs infrequently and, as the article points out, the solid variant is exceedingly rare in the spine. While MRI can be very helpful in formulating a differential diagnosis and differentiating S-ABC from more typical cystic ABC, imaging studies cannot always differentiate S-ABC from other benign bone lesions. Performing an incisional biopsy with intra-operative frozen section is an important first step in our approach to treatment of this and other forms of ABC. Traditional treatment of ABC with intralesional curettage and bone grafting produced recurrence rates of 10–60 % [2]. To limit recurrence, we recommend a four-step approach to treatment of ABC, including the solid variant form. This includes (1) intralesional curettage, (2) cauterization of the osseous cyst wall, (3) extended curettage with a high-speed diamond burr, and (4) dilute (5 %) phenol application [3]. Titanium instrumentation may be necessary after removal to reestablish spinal stability. As in this case, arterial embolization can be used as an adjunct to surgical excision.

Solid variant of aneurysmal bone cyst on the cervical spine of a child: case report, differential diagnosis and treatment rationale

Despite numerous descriptive publications, the nature, character, differential diagnosis and optimal treatment of aneurysmal bone cysts (ABCs), remain obscure. The authors report a case of the solid variant of aneurysmal bone cyst (S-ABC) occurring in the posterior components and body of C7 vertebra focusing on the differential diagnosis and surgical treatment rationale. Right shoulder and neck pain were the presenting symptoms of 9-year-old boy. Torticollis developed later on but no neurological deficit was found. Imaging revealed an osteolytic lesion with significant extraosseous extension. Although diagnosis favoured an ABC, imaging studies did not provide clear diagnostic criteria. CT guided biopsy performed preoperatively was also not directly diagnostic. Given that differential diagnoses included S-ABC but also giant cell tumor (GCT) of bone, decision was made to proceed with a staged, back and front, complete resection of the affected bony elements of C7. Preoperative spinal angiography showed supply to the tumor from the right ascending and deep cervical artery territories. Particle embolization was not performed due to the presence of ipsilateral supply to the anterior spinal artery at the C6 level and contralateral supply at the C7 level. Intraoperatively, histology taken from posterior elements, although again not clearly diagnostic, favoured S-ABC variant rather than GCT. Thus, initial plan was revised and anterior surgery was postponed as the extent of the dissection would have been dependent on the presumed diagnosis. The final histological report confirmed the diagnosis of an S-ABC. In view of this, it was decided to embolize the lesion to avoid a second stage anterior surgery. At embolization, repeat spinal angiography showed reduced tumor blush following the surgery. Distal branches of the deep cervical artery were occluded with platinum coils (avoiding the risks associated with the use of particles or liquid embolic agents). No further procedure was planned. Imaging and histological pattern of this specific type of ABC, differential diagnosis from GCT and the surgical protocol followed with the patient consist of an interesting case of revising the initial plan, according to the upcoming histological reports.

Solid Variant of Aneurysmal Bone Cyst of the Left Parietal Bone without Preceding Trauma

We report the case of a 17-year-old girl with an indolent, smooth swelling of the left cranial vault that had been developing for 2 months. Complete surgical excision was performed and the defect was closed using artificial bone cement. The integrity of the dura mater was conserved and the patient recovered without neurological deficit. Magnetic resonance imaging (MRI) controls 6 and 18 months after the operation did not find signs of recurrence. The lesion consisted of an elastic bone shell containing bony trabeculae with soft brown-greyish tissue and posthemorrhagic dark fluid. Histological assessment found CD68 positive multinucleated giant cells in a highly cellular fibroblastic matrix surrounding bony lamellar structures, without signs of inflammation or malignancy. Hyperparathyroidism was ruled out by normal serum values for parathyroid hormone, calcium, phosphate, and alkaline phosphatase. Histologically, first diagnosis was giant cell reparative granuloma and reference pathology disclosed aneurysmal bone cyst. The solid variant of aneurysmal bone cyst and the giant cell reparative granuloma can be histologically indistinguishable. Both lesions are only rarely encountered in cranial bones and most published cases affected the cranial base or the jaw, mainly in children or young adults. From a clinical point of view, classification into "outward" lesions (osteolysis of external parts of the vault with preservation of internal tabula) and "inward" lesions (intracranial multicystic lesions with raise of intracranial pressure) has been proposed. Three phases of development can be identified, and spontaneous involution has been described. Both entities are benign, but because in several cases an underlying malignant disease has been found, complete resection and regular follow-up by MRI are recommended.

Solid variant of aneurysmal bone cyst in the tibia treated with simple curettage without bone graft: a case report

The solid variant of aneurysmal bone cyst (solid ABC) is rarely encountered in long bones and appropriate treatment for this disease remains unclear. We experienced a 13-year-old boy suffering from pain in his left knee caused by solid ABC. Simple curettage of the bone lesion without any adjuvant therapy and a bone graft gave immediate pain relief. Histological examination of the surgical specimen showed typical features of solid ABC, and cycloxygenase-2 (COX-2) expression was confirmed in giant cells with a background of spindle cells by immunohistochemistry. Magnetic resonance imaging showed that soft tissue edema surrounding the lesion was improved two months after surgery and there was no indication of recurrence two years after surgery.If COX-2 secreted from the tumor induces soft tissue edema, simple curettage of the bone lesion seems to be a reasonable treatment for solid ABC and is able to minimize invasive treatment of the patients.

A novel t(6;13)(q15;q34) translocation in a giant cell reparative granuloma (solid aneurysmal bone cyst)

Aneurysmal bone cyst is a rapidly growing and locally aggressive lesion that commonly affects children and young adults. Initially regarded as a reactive process, primary aneurysmal bone cyst is now widely accepted as a neoplasm owing to recent findings of recurrent clonal chromosomal alterations, mostly t(16;17)(q22;p13). However, other infrequent chromosomal rearrangements have also been reported. Giant cell reparative granuloma, previously regarded as a nonneoplastic process and histologically indistinguishable from the solid variant of aneurysmal bone cyst, is frequently seen in the gnathic bones and the short tubular bones of the hands and feet. Here we present such a case of giant cell reparative granuloma (solid aneurysmal bone cyst) in the finger of a 63-year-old white man. Cytogenetic analysis revealed a novel alteration involving a reciprocal translocation between 6q and 13q, with a karyotype of 46,XY,t(6;13)(q15;q34),del(20)(q13.1).

A clinicopathological study of giant cell tumor of small bones

Background and purpose. Giant cell tumor (GCT) of the small bones (small-bone GCT) is usually rare and considered somewhat different from conventional GCT. The purpose of this study was to investigate and report the clinicopathological features of 11 cases with small-bone GCT.Materials and methods. Patient information was obtained with the help of questionnaires. X-rays and paraffin blocks obtained from several institutions were clinically, radiographically, and histologically evaluated.Results. Small-bone GCT was observed in younger patients compared to conventional GCT; 5 of the 11 (45%) patients were below 20 years of age, whereas the corresponding figure for all GCT patients is 16% in Japan. Excessive cortical bone expansion is a special feature. There were two cases of recurrence and one case of lung metastasis; the primary lesion was in the hand for all three cases. In contrast, no primary lesion of the foot recurred or metastasized. Varying degrees of positive p63 immunostaining were observed in all examined cases (n = 9) of small-bone GCT but were negative in case of giant cell reparative granuloma (GCRG) and solid variant of aneurysmal bone cyst (ABC). One case that demonstrated high-intensity positive staining had two episodes of recurrence.Conclusion. Small-bone GCT tends to develop in younger patients than does conventional GCT. Primary GCTs of the hand may be biologically more aggressive than those of the feet. The p63 immunostaining may be useful not only for differential diagnosis but also for prognostication of small-bone GCT.

Solid variant of aneurysmal bone cyst of the thoracic spine: a case report.

IntroductionThe solid variant of aneurysmal bone cyst is rare, and only 13 cases involving the spine have been reported to date, including seven in the thoracic vertebrae. The diagnosis is difficult to secure radiographically before biopsy or surgery.Case reportAn 18-year-old Hispanic man presented to our facility with a one-year history of left chest pain without any significant neurological deficits. An MRI scan demonstrated a 6 cm diameter enhancing multi-cystic mass centered at the T6 vertebral body with involvement of the left proximal sixth rib and extension into the pleural cavity; the spinal cord was severely compressed with evidence of abnormal T2 signal changes. Our patient was taken to the operating room for a total spondylectomy of T6 with resection of the left sixth rib from a single-stage posterior-only approach. The vertebral column was reconstructed in a 360° manner with an expandable titanium cage and pedicle screw fixation. Histologically, the resected specimen showed predominant solid fibroblastic proliferation, with minor foci of reactive osteoid formation, an area of osteoclastic-like giant cells, and cyst-like areas filled with erythrocytes and focal hemorrhage, consistent with a predominantly solid variant of aneurysmal bone cyst. At 16 months after surgery, our patient remains neurologically intact with resolution of his chest and back pain.ConclusionsBecause of its rarity, location, and radical treatment approach, we considered this case worthy of reporting. The solid variant of aneurysmal bone cyst is difficult to diagnose radiologically before biopsy or surgery, and we hope to remind other physicians that it should be included in the differential diagnosis of any lytic expansile destructive lesion of the spine.

Solid variant of aneurysmal bone cyst of the heel: a case report

IntroductionAn aneurysmal bone cyst is a benign but often rapidly expanding osteolytic multi-cystic osseous lesion that occurs as a primary, secondary, intra-osseous, extra-osseous, solid or conventional lesion. It frequently coexists with other benign and malignant bone tumors. Although it is considered to be reactive in nature, there is evidence that some aneurysmal bone cysts are true neoplasms. The solid variant of aneurysmal bone cyst is a rare subtype of aneurysmal bone cyst with a preponderance of solid to cystic elements. Such a case affecting the heel, an unusual site, is reported.Case presentationA 26-year-old Caucasian man presented with pain and swelling in his left lower extremity. A plain radiograph demonstrated an intra-osseous, solitary, eccentric mass in the front portion of the left heel. Computed tomography and magnetic resonance imaging scans showed that the lesion appeared to be sub-cortical, solid with a small cystic portion without the characteristic fluid-fluid level detection but with distinct internal septation. Bone images containing fluid-fluid levels are usually produced by aneurysmal bone cysts. The fluid-fluid level due to bleeding within the tumor followed by layering of the blood components based density differences, but it was not seen in our case. An intra-lesional excision was performed. Microscopic examination revealed fibrous septa with spindle cell fibroblastic proliferation, capillaries and extensive areas of mature osteoid and reactive woven bone formation rimmed by osteoblasts. The spindle cells had low mitotic activity, and atypical forms were absent. The histological features of the lesion were consistent with the solid variant of an aneurysmal bone cyst.ConclusionSolid aneurysmal bone cysts have been of great interest to pathologists because they may be mistaken for malignant tumors, mainly in cases of giant cell tumors or osteosarcomas, because of cellularity and variable mitotic activity. It is rather obvious that the correlation of clinical, radiological and histological findings is necessary for the differential diagnosis. The eventual diagnosis is based on microscopic evidence and is made when a predominance of solid to cystic elements is found. The present case is of great interest because of the nature of the neoplasm and the extremely unusual location in which it developed. Pathologists must be alert for such a diagnosis.

Solid variant of aneurysmal bone cyst of the hamate

Solid variant of aneurysmal bone cyst is a variant of aneurysmal bone cyst in which the predominant histology is that of the solid material of a cystic aneurysmal bone cyst. In this article, we present a patient with solid variant of aneurysmal bone cyst of the hamate and discuss the differential diagnosis and current treatment for this lesion.

First report of a solid variant of aneurysmal bone cyst in the os sacrum

We report on a 19-year-old woman with a rapidly growing, solid variant of aneurysmal bone cyst (solid ABC) in the right part of the lateral mass of the sacrum. On admission, the magnetic resonance imaging (MRI) scan disclosed an inhomogeneous low intensity mass right of the centre of the os sacrum with a diameter of 38 x 64 mm and a height of 56 mm on T1 and T2 weighted images. The mass showed homogenous high signal intensity on Gd-enhanced images. Computed tomography demonstrated an expansile osteolytic lesion and (99m)Tc-methylene diphosphonate bone scintigraphy revealed uniform accumulation in the lesion. The histological evaluation showed a proliferation of fibroblasts, histiocytes, chronic inflammatory cells and numerous multinucleated giant cells. Nevertheless, the cells were devoid of nuclear atypia. A cystic component was not observed. In spite of thorough curettage, the patient suffered from recurrence and severe neurological deficits. A review of the literature revealed no previous cases of solid ABC in the sacrum.