Neglected huge chest wall mass. A case report of fibrous dysplasia

Introduction fibrous dysplasia is a slow-growing bone tumor and is caused by the failure of bone maturation. It is usually asymptomatic thus it is generally found incidentally in radiologic evaluations. Computed tomography is the best radiologic modality for its evaluation. The characteristic findings are ground-glass lesions surrounded by a rim or shell of reactive bone. Presentation of case This study presents a 52-year-old male patient with a huge chest wall tumor arising from the posterolateral aspect of the right fourth to seventh ribs measuring 38 cm. He underwent a thoracotomy and the tumor was resected. For safe margin, the third and eighth ribs were also resected. The defect was reconstructed with a prolene mesh patch and a pectoralis major flap. The final pathology report stated a tumor composed of spindle cells without pleomorphism or mitotic figures with intervening branching and anastomosing bone trabeculae. The margins were tumor-free and on the follow-up, the patient's condition was decent. Discussion Primary tumors of the rib account for 5 % to 7 % of all primary bone neoplasms. Fibrous dysplasia makes up 0.8 % of primary bone tumors. Fibrous dysplasia usually causes no symptoms although it can get massive enough to get symptomatic. Its diagnosis is made through clinical, radiological, and histopathological investigations. CT scan findings are the cornerstone for radiologic evaluations. An individualized approach based on the patient's age and symptoms should be considered. Conclusion Considering that the malignant degeneration of the tumor is uncommon, early diagnosis and surgical resection of the tumor can be curative.


Introduction
Fibrous dysplasia first came to notice in 1938 by Lichtenstein [1]. It occurs as a result of bone maturation failure from the primitive stage to the lamellar stage. Bone mineralization and remodeling are also impaired under mechanical stress [2]. Although its etiology is not entirely recognized, mutation of signal-transducing G proteins encoded by GNAS1 on chromosome 20 is likely associated with fibrous dysplasia. Malignant degeneration is uncommon [3]. The disease affects men and women equally and can occur at any age although the peak prevalence is in the third decade of life [4]. Based on systemic findings and bone involvement, fibrous dysplasia is categorized into four distinct classes: single bone involvement (monostotic), multiple bone involvement (polyostotic), or accompanying McCune-Albright or Mazabraud disease [5][6][7]. Monostotic fibrous dysplasia is the most common form of the disease which is usually asymptomatic and is found incidentally. However, based on the size and location of the tumor, it can present itself with varying symptoms such as bone pain, deformity, stress fractures, and pathologic fractures [5,[8][9][10].
Radiologic studies can facilitate the diagnosis. Bone lesions have ground-glass patterns in plain x-ray images due to the replacement of normal bone with radiolucent tissue. Bone lesions are surrounded by rims or shells of reactive bone and are a characteristic finding [5,11]. Bone scintigraphy can help estimate the severity of the disease. The lesions have high radionucleotide uptake but it diminishes over time as the lesions mature [12]. Computed tomography is the best modality for evaluation since the lesions enhance in a contrast study [5]. Magnetic resonance imaging can add some useful information to CT scan findings [13]. We present a case of fibrous dysplasia with a huge chest wall mass causing dyspnea. This work has been reported in line with the SCARE criteria [14].

Case presentation
This study presents a 52-year-old middle-eastern male patient with a huge slow-growing chest wall mass located on the right chest wall. His past medical and surgical history was unremarkable and he had no known allergies albeit he was a smoker. The patient's vital signs were all within the normal range (blood pressure 110/75 mmHg, pulse rate 76 bpm, respiratory rate 17 rpm, temperature 37.3 • C, blood oxygen saturation 95 %). Except for the large firm chest wall mass located on the right chest wall, his physical examination was unremarkable. Chest Xray and computed tomography (CT) displayed a giant intramedullary lesion with a ground-glass center and thickening of the cortex arising from the posterolateral aspect of the right fourth to seventh ribs measuring 38 cm in diameter. The pulmonary function test (PFT) of the patient, who was a smoker, revealed the following: FEV1, 55 %; FVC, 53 %; FEV1/FVC 0.79; FEF25-75: 47 %. A 3-dimensional reconstruction of the CT scan was performed and in Fig. 1 the size and the extension of the lesion can be seen. A solid lesion, which destroyed the fourth to seventh ribs with axial dimensions of approximately 36 × 18 cm was detected in the CT scan. The previous pathology report was inconclusive and reported a spindle cell lesion. The patient was discussed with a multidisciplinary tumor board including thoracic surgeons and oncologists then they agreed upon a surgical excision to diagnose and treat the patient. Anesthesia was induced and the patient was intubated with a doublelumen endotracheal tube. The patient was put in the left lateral decubitus position. Thoracotomy was initiated by an elliptical incision. The thorax was opened with a right lateral thoracotomy. Thereafter, we observed a mass measuring about 36 × 18 × 11 cm in dimensions adhering to the fourth to seventh ribs. It had adhesion neither to the lung nor the heart. The tumor was resected and for safe margins, the third and eighth ribs were also resected (Fig. 2). The defect size was 40 × 25 cm in diameter. The defect was reconstructed with a prolene mesh patch and bone cement. The mesh was then covered with pectoralis major pedicled flap. A thoracic tube was placed in the apex of the lung. The patient was monitored in the ICU for two days and then was transferred to the thoracic surgery ward on the third day. The thoracic tube, discharging no fluids, was removed on the fourth day. Finally, the patient was discharged from the hospital on the sixth day. The patient was followed up periodically. The final pathology report stated: "a tumor composed of spindle cells without pleomorphism or mitotic figures with intervening branching and anastomosing bone trabeculae". Bone trabeculae were woven without a prominent osteoblastic rim. Furthermore, the margins were tumor-free (Fig. 3). On the follow-up, after 30 days, the patient's condition was excellent. He had no complaints and his wounds had healed. The post operation CT scan release expanded lung and normal chest wall (Fig. 4).

Discussion
Primary chest wall tumors are infrequent. Primary tumors of the rib constitute 5 % to 7 % of all primary bone neoplasms. Benign bone tumors of the chest wall consist of osteochondroma, fibrous dysplasia, chondroma, and eosinophilic granuloma [15].
Fibrous dysplasia accounts for 0.8 % of primary bone tumors and was first described by Lichtenstein in 1938. It is characterized by the replacement of normal bone with fibrous tissue and immature bone structures [1]. The likely etiology is mutations in GNAS gene 20q. This gene encodes Gs alpha in the target cells which are responsible for bone cell alternations [3].
Fibrous dysplasia usually produces no symptoms. The lesions are detected accidentally during radiological investigations. However, in rare cases, they may become symptomatic as they grow in size. They can also cause pathologic fractures, neuropathy, and deformities [16].
Clinical, radiologic, and histopathological investigations are the pillars for the diagnosis of fibrous dysplasia. CT scan findings are the cornerstone of radiologic evaluations. The "ground-glass" appearance is the result of medullary space replacement by the mixture of woven bone and fibrous components [3]. Polymerase chain reaction (PCR) can be utilized for the diagnosis. Missense point mutations in the G s α at the Arg 201 codon are positive and the tumor cells do not express the proliferating cell nuclear antigen [17]. Histologic features consist of cellular fibrous dysplasia containing a proliferation of bland and uniform spindle cells with sparse mitotic activity [18].
In an asymptomatic patient with typical radiologic features consistent with the diagnosis of fibrous dysplasia, a biopsy can be withheld. In that case, conservative management with a close clinical and radiological assessment for tumor progression is reasonable [5]. Newly   diagnosed patients with multiple lesions should be evaluated to rule out metabolic and endocrine disorders accompanying the disease [5]. Bisphosphonates have shown promising results in the medical treatment of the symptomatic polyostotic variant of the disease [19].
Surgical intervention is indicated when symptomatic lesions or deformities and pathologic fractures are present. Regarding skeletal maturity and the possibility of tumor progression and maturation, age is an important factor in decision-making for surgical treatment [11,12].
Complete resection of the lesion is sufficient and the defect has to be reconstructed. In our case, we used both a pectoralis major flap and a prolene mesh. As far as we know, few reports have described huge fibrous dysplasia of the chest wall. Mahadevappa et al. reported a case report of a 70-year-old female with a chest wall mass measuring 10 × 9 cm in size, However, this tumor was smaller than the one we observed in our case [20].

Conclusion
Fibrous Dysplasia is a rare bone tumor with slow progression. Considering that the malignant degeneration of the tumor is uncommon, early diagnosis and surgical resection of the tumor can be curative in symptomatic patients.

Consent
Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal on request.

Ethical approval
Investigations were in accordance with Helsinki Declaration of 1964 and all subsequent revisions.

Sources of funding
This study did not receive any specific backing from funding agencies in the public, commercial, or non-profit sectors.