Abstract
Background/Aim: Giant cell tumor of bone (GCTB) is a locally aggressive neoplasm that typically occurs in the ends (epiphyses) of long bones of young adults. Flat bones are uncommon sites of involvement. Herein, we describe an unusual case of pathologically proven GCT of the acromion. Case Report: The patient was a 39-year-old woman with no history of trauma who presented with a 3-month history of right posterior shoulder pain. Physical examination revealed mild swelling and tenderness in the posterior aspect of the right shoulder. Plain radiograph showed a purely lytic lesion, suggestive of a bone tumor. Computed tomography demonstrated an intraosseous lytic lesion with associated cortical thinning and lack of periosteal reaction. On magnetic resonance imaging, the lesion exhibited slightly higher signal intensity compared to skeletal muscle on T1-weighted sequences and heterogeneous high signal intensity on T2-weighted sequences. Strong enhancement was observed following gadolinium administration. The lesion was treated by extensive curettage with adjuvant therapy comprising ethanol and the remaining cavity was filled with polymethylmethacrylate bone cement. Histologically, the lesion was composed of round or spindle-shaped mononuclear cells admixed with numerous osteoclast-like giant cells. Immunohistochemically, the mononuclear neoplastic cells were diffusely positive for H3.3 G34W. The patient was asymptomatic and there was no evidence of local recurrence or distant metastasis 5 months after surgery. Conclusion: Although rare, acromial GCTB should be considered in the differential diagnosis of posterior shoulder pain, especially in young and early middle-aged adults.
Giant cell tumor of bone (GCTB) is an intermediate, locally aggressive but rarely metastasizing neoplasm. It accounts for 4-5% of all primary bone tumors and typically affects the ends (epiphyses) of long bones (1). GCTB may occur at any age but has a peak incidence in the third and fourth decades of life, with a slight female predominance. Pain is the most common symptom. Swelling, decreased range of motion (ROM) of the adjacent joint, and local tenderness are also common clinical characteristics. Pathological fractures are observed in 5-12% of cases (1). The main treatment modality for GCTB is surgery which includes extensive curettage with local adjuvants and en bloc resection. Denosumab may be used as a treatment for surgically unresectable GCTBs or when resection is likely to result in severe morbidity for skeletally mature adolescents and adults (2). In general, the local recurrence rate of GCTB is very high for curettage alone (27-65% of cases), decreases for curettage with adjuvant therapy (12-27% of cases), and is quite low for en bloc resection (0-12% of cases) (3, 4). Malignant transformation occurs in less than 1% of cases (4).
The acromion is a very rare site for the development of primary tumors. The diagnosis of acromial tumors may be delayed because of a low level of suspicion. Malignant tumors are more frequent compared to benign lesions (5). Herein, we present an unusual case of GCT of the acromion and discuss the differential diagnosis of this peculiar neoplasm. Written informed consent was obtained from the patient to publish this case report and accompanying images.
Case Report
A 39-year-old woman presented with a 3-month history of persistent right posterior shoulder pain. She had no history of shoulder trauma. Physical examination showed mild soft tissue swelling and tenderness in the posterior aspect of the right shoulder. The range of motion (ROM) of the affected shoulder was normal. The laboratory data were within normal limits. Plain radiographs revealed a well-defined, lytic lesion in the acromion (Figure 1). Computed tomography (CT) demonstrated an intraosseous lytic lesion with associated cortical thinning (Figure 2). There was no evidence of periosteal reaction or internal mineralization. On magnetic resonance imaging (MRI), the lesion exhibited slightly higher signal intensity compared to skeletal muscle on T1-weighted sequences (Figure 3A) and heterogeneous high signal intensity on T2-weighted sequences (Figure 3B). Strong enhancement was seen following gadolinium administration (Figure 3C). There was no obvious soft-tissue or intra-articular extension. Based on these findings, primary bone tumor was suggested, including GCTB and solitary plasmacytoma of bone (SPB).
Anteroposterior radiograph of the right shoulder reveals a well-defined, lytic lesion (arrows) in the acromion.
Axial computed tomography of the right shoulder shows an intraosseous lytic lesion (arrows) with cortical thinning in the acromion.
Axial magnetic resonance images of an intraosseous lesion in the right acromion. The lesion shows slightly higher signal intensity compared to skeletal muscle on T1-weighted sequence (A) and heterogeneous high signal intensity on T2-weighted sequence (B). Contrast-enhanced fat-suppressed T1-weighted sequence (C) demonstrates strong enhancement of the lesion.
An incisional biopsy was performed, and the pathological diagnosis was GCTB. The patient subsequently underwent extensive intralesional curettage with a high-speed burr. Following curettage, 99.5% ethanol was applied meticulously to the inner surface of the cavity with a cotton swab for a period of 10 min. After extensive washing with normal saline solution, the cavity was filled with polymethylmethacrylate bone cement. Microscopically, the tumor consisted of round or spindle-shaped mononuclear cells admixed with numerous osteoclast-like giant cells (Figure 4A). Atypical mitotic figures were absent. Immunohistochemically, the mononuclear stromal cells were diffusely positive for H3.3 G34W (Figure 4B). These findings confirmed the diagnosis of conventional GCTB.
Histological and immunohistochemical findings of giant cell tumor of bone. The tumor is composed of round or spindle-shaped mononuclear cells admixed with numerous osteoclast-like giant cells (A) (hematoxylin and eosin staining, original magnification ×100). Immunohistochemically, the mononuclear neoplastic stromal cells are diffusely positive for H3.3 G34W (B) (original magnification ×200).
The postoperative course was uneventful. The patient returned to normal activities within 1 month after surgery. At 5 months follow-up, the patient was asymptomatic and there was no evidence of local recurrence (Figure 5) or distant metastasis.
Follow-up radiographs of the right shoulder 5 months after surgery.
Discussion
In recent years, there has been a breakthrough in the molecular and immunohistochemical profile of GCTB. The vast majority of GCTBs harbor H3.3 histone A (H3-3A) gene mutations (6-8). In addition, the most frequent mutation (H3.3 G34W) can readily be detected using immunohistochemistry and is highly specific in differentiating GCTB from its histological mimics (9). Our case also showed nuclear expression of H3.3 G34W consistent with previous results (9).
A variety of benign, intermediate, and malignant tumors may occur in the scapula (10). However, primary tumors and tumor-like lesions of the acromion are extremely rare, and little literature is available regarding their clinicopathological characteristics and management. To the best of our knowledge, only four cases of acromial GCTB have been reported (11, 12). As previously reported, pain was the major complaint in our case. Radiographically, acromial GCTB usually demonstrates a lytic lesion with a well-defined, non-sclerotic margin and no intralesional mineralization and can mimic malignant tumors, such as metastasis or plasmacytoma/myeloma in the older patients. Secondary aneurysmal bone cyst (ABC) formation may be seen on MRI (12).
Surgical management is the mainstay of treatment for patients with GCTB. The accepted procedure is curettage and filling of the defect with bone graft, bone cement, or bone substitute (13). Most orthopaedic surgeons mainly perform extensive curettage using a high-speed burr. Various adjuvant therapies, such as ethanol, phenol, hypertonic saline, and liquid nitrogen, have been used to reduce the postoperative recurrence rate (14), as in our case. Another treatment option represents the en bloc resection. Previously, Sherwani et al. reported a case of aggressive GCTB of the acromion and its management with a partial scapulectomy (12). However, there is currently no consensus on the optimal treatment of acromial GCTB. It should be kept in mind that patients should be clearly informed of the risks and benefits of each treatment option.
The differential diagnosis of the present case may include chondroblastoma and SPB. Chondroblastoma accounts for <1% of all primary bone tumors and most commonly occurs in the second to early third decades of life, with a male predominance. About 75% of chondroblastomas arise in the epiphyses of long bones (15). Involvement of the flat bones is uncommon. Chondroblastoma is usually smaller in size compared to GCTB. Radiographically, chondroblastoma usually presents as a well-demarcated, lytic lesion with thin sclerotic margins. Unlike GCTB, intralesional mineralization is frequently found in chondroblastoma. Peritumoral edema or secondary ABC formation may be seen on MRI. Histologically, chondroblastoma is characterized by a sheet-like proliferation of ovoid to polygonal cells with eosinophilic cytoplasm. Variable numbers of osteoclast-like giant cells are often present. Pericellular lace-like or chicken-wire calcification is characteristic (15). H3.3 K36M immunohistochemistry is highly specific for the diagnosis of chondroblastoma (16). Surgery is the treatment of choice for chondroblastoma and includes intralesional curettage with or without local adjuvants and en bloc resection. The local recurrence rate ranges from 10% to 35% (17), depending somewhat on the initial site. Plasmacytoma/myeloma is the second most common primary malignant tumors of the acromion (5). SPB is a localized, intraosseous neoplasm composed of monoclonal plasma cells, with no evidence of other osseous lesions (18). It most commonly occurs in middle-aged and older adults, with a male predominance. SPB primarily arises in red marrow-containing bones, such as vertebra and pelvis (19). Some patients have a small monoclonal protein (also called M protein) detectable in the serum and/or urine (18). Radiographically, SPB is non-specific and can present as a well-circumscribed, lytic lesion without identifiable matrix. CT may be helpful in evaluating the risk of pathological fractures. On MRI, the lesion displays isointense signal intensity on T1-weighted images and high signal intensity on T2-weighted images. Contrast-enhanced MRI shows marked enhancement (5). Radiotherapy, with or without chemotherapy, is the treatment of choice. Surgery should be reserved for the treatment of pathological fractures or neurological complications. In the present case, it was difficult to differentiate SPB from GCTB based on imaging features alone.
In conclusion, we described an unusual case of conventional GCTB of the acromion. Acromial GCTB should be considered in the differential diagnosis of persistent posterior shoulder pain, particularly in young and early middle-aged adults.
Acknowledgements
This study was supported in part by the Japan Society for the Promotion of Science KAKENHI (21K09336).
Footnotes
Authors’ Contributions
JS provided direct patient care and collected the data. JN performed the operation and drafted the article. YC reviewed the article. All Authors read and approved the final article.
Conflicts of Interest
The Authors declare no conflicts of interest associated with this article.
- Received September 1, 2023.
- Revision received September 18, 2023.
- Accepted September 19, 2023.
- Copyright © 2024 The Author(s). Published by the International Institute of Anticancer Research.
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY-NC-ND) 4.0 international license (https://creativecommons.org/licenses/by-nc-nd/4.0).
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