Rapid growth of a solitary fibrous tumor of the pleura after slow long-term progression: a case report

Abstract

Background

Solitary fibrous tumors (SFTs) of the pleura are usually benign. We present a case of SFT of the pleura which grew rapidly after slow long-term progression.

Case presentation

A 78-year-old man was referred to our hospital for left-sided back pain and shortness of breath. He was found to have a left mediastinal mass at 15 years of age. He remained asymptomatic for 60 years, and chest computed tomography (CT) during treatment of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis revealed that the mediastinal tumor was 8.0 cm in diameter. The size remained unchanged for 3 years but increased to 15.0 cm over the next 5 years. As the left main pulmonary artery was compressed by the mass, there were concerns regarding the worsening of haemodynamics and exacerbation of symptoms of respiratory distress. A sixth-rib intercostal thoracotomy with a posterolateral incision was performed to remove the large tumor. Perioperative steroid administration (methylprednisolone 125 mg/day) and positive pressure ventilation were administered to prevent re-expansion of the pulmonary oedema. The patient was discharged following an uneventful course. The tumor was pathologically diagnosed as an SFT with no malignant findings.

Conclusion

SFTs require surgical intervention because of their potential for rapid growth.

Background

Solitary fibrous tumors (SFTs) account for less than 5% of all tumors arising from the pleura and have an estimated incidence of 2.8 per 100,000 individuals [1]. SFTs occur in a wide age range, predominantly in patients aged 60–70 years, and without any sex predilection. Patients with SFTs present with dyspnea, chest pain, cough, clubbing of fingers, and hypoglycemia, although most cases are asymptomatic and detected incidentally [1]. SFTs of the pleura exhibit benign behavior in the majority of cases. However, infrequently, they can grow rapidly [2]. We report a case of rapid growth of an SFT of the pleura with benign features after 60 years of slow progression.

Case presentation

A 78-year-old man was referred to our hospital for left-sided back pain and shortness of breath. He had a history of spinal caries, and a left mediastinal mass was detected at the age of 15 years, which was followed up for several decades (detailed information from the follow-up period was not available). Computed tomography (CT) performed at the time of initial follow-up of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis showed that the mediastinal mass was 8 cm in diameter. Oral prednisolone for ANCA-associated vasculitis was administered for three years, and the mediastinal mass showed no change in size during this period. However, the tumor increased to 11.8 cm over the next two years, and then to 15.0 cm over the next three years (Fig. 1A, B). The patient was referred to our hospital for surgery. As the left main pulmonary artery was compressed by the mass (Fig. 1C), there were concerns regarding the worsening of haemodynamics and symptoms of respiratory distress becoming more severe. Surgery was planned after bronchial artery embolization to prevent massive intraoperative haemorrhage. Although embolization was unsuccessful due to the strong meandering of the descending aorta, vessels feeding the tumor from the aorta and intercostal arteries were detected (Fig. 1D).

Fig. 1

(A) Chest computed tomography (CT) image showing an 8.0 cm tumor with no change in size for 3 years. (B) The tumor size increased to 15.0 cm over the next 3years. (C) Contrast-enhanced CT image showing the tumor compressing the main trunk of the left pulmonary artery. (D) 3D-CT shows that the tumor is fed from a branch of the descending aorta that is strongly tortuous

Subsequently, 6th rib-bed intercostal thoracotomy with a posterolateral incision was performed to remove the large tumor. The tumor occupied the entire thoracic cavity (Fig. 2A) and caused compression and thinning of the lung parenchyma (Fig. 2B). Although adhesions to the lung and chest wall were found, the tumor did not infiltrate the adjacent structures, including the left main pulmonary artery. The lesion was manually dissected from the adjacent structures without injury. The tumor was pedunculated on the dorsal pleura of the seventh intercostal space and originated from the parietal pleura of the chest wall. It was firm and elastic, had a solid component, and was covered with a capsule (Fig. 2C). The thinned lungs promptly expanded with positive-pressure ventilation after tumor resection (Fig. 2D). The operative time was 319 min and the blood loss amounted to 962 g. The tumor weighed 928 g. On gross examination, it was 14.0 × 11.5 × 8.5 cm in size, whitish in color, and lobulated (Fig. 3A). Pathologically, it was composed of atypical weakly spindle-shaped cells that were arranged in a bundle-like arrangement alternating with collagen fibers, and the nuclear fission pattern was inconspicuous, with 1/10 high-power field (HPF) at most. Areas of high cell density, suspected tumor necrosis, and ischemic necrosis were unremarkable (Fig. 3B). Immunohistochemical staining revealed STAT6 (+) and an MIB1 index of 5.2%. Accordingly, the tumor was diagnosed as an SFT without malignant features (Fig. 3C). The surgical margins were negative. According to the scoring system proposed by Demicco et al., 2 the patient was considered to have an intermediate risk of recurrence (age: 1 [> 50 years], tumor size: 2 [10–15 cm], mitotic activity: 1 [1–3/10 HPF], and necrosis: 0 [< 10%]). To prevent re-expansion of the pulmonary oedema, positive pressure ventilation with perioperative steroids (methylprednisolone 125 mg/day) was administered until postoperative day (POD) 1. The patient was discharged on POD 13 following an uneventful course.

Fig. 2

(A, B) The tumor (black star) occupies the thoracic cavity, and the lungs (white star) are compressed and thinned. (C) The tumor is firm, elastic, has a solid component, and is covered with a capsule. (D) The lungs show relatively good expansion after tumor resection

Fig. 3

(A) The tumor was covered by a capsule and was firm and elastic. A whitish lobulated internal mass was observed on the split face. (B) Haematoxylin and eosin staining reveals atypical weakly spindle-shaped cells arranged in a bundle-like arrangement alternating with collagen fibers, and the nuclear fission pattern is inconspicuous (magnification ×200). (C) Immunohistochemical staining showing an MIB1 index of 5.2%

Discussion and conclusions

SFTs are relatively rare mesenchymal tumors. As the tumor grows, SFT can cause respirocirculatory failure by compressing the lungs, diaphragm, or heart. In this case, the patient was diagnosed with a mediastinal mass at the age of 15 years, but became symptomatic only after 60 years. Circulatory failure due to compression of the left main pulmonary artery triggered the symptoms, which could be potentially fatal [3]. Surgical resection should be considered for suspected SFTs with a tendency to increase in size. However, large SFTs may show hypervascularity and extensive collateral vascularity [4]. In the present case, we detected abnormal feeding vessels from the aorta and intercostal arteries using preoperative angiography, and the large SFT was resected with minimal intraoperative blood loss because of the detection of the vessels feeding the tumor. However, if preoperative embolization had been successful, bleeding would have been even less. Thus, preoperative angiography is a valuable modality for identifying major nutritional vessels and surgical planning for large SFTs.

SFTs have the potential for rapid growth after more than 5 years. Kubo et al. reported an SFT that remained unchanged in size for 7 years, followed by rapid growth [5]. Similarly, Okimoto et al. reported an SFT that showed rapid growth after 16 years of follow-up [6]. In these case reports, the cause of tumor growth was considered to be malignant transformation. Some cases show rapid growth due to intratumoral haemorrhage [7,8]. In the present case, there were no histological findings of malignant transformation or intratumoral haemorrhage. The duration of steroid administration, which may promote tumor growth, 9 did not coincide with the period of tumor enlargement. However, it is possible that ANCA-associated vasculitis, which was treated in the three years prior to the rapid growth, caused tumor growth. Similar to other autoimmune diseases, the pathogenesis of ANCA-associated vasculitis and immunosuppressive therapy are associated with the risk of cancer development due to chronic immune stimulation-induced malignant tissue degeneration, decreased immune surveillance, and immunosuppressant drug carcinogenicity [10]. These mechanisms have a long latent period, and the rapid growth of the benign SFT may have been related to ANCA-associated vasculitis. Thus, even SFTs with benign histological findings have the potential for rapid growth.

The prognosis is good for patients with benign SFTs treated with complete surgical resection, which can lead to long-term survival without recurrence [11]. However, there are reports of late recurrence more than 5 years after resection, and the clinical behavior of individual tumors is difficult to predict. Regarding prognosis prediction and risk of recurrence, Demicco et al. proposed a scoring system based on clinicopathological prognostic factors, which may be useful [2]. In this case, the histology was benign with minimal invasion of the surrounding area, and complete resection was possible. Nevertheless, according to Demicco scoring system, this patient was considered to have moderate risk; therefore, long-term follow-up is required.

In conclusion, SFTs require surgical treatment due to their potential for rapid growth.