Characteristics of patients with synovial sarcoma
The characteristics of patients with SS are presented in Table 1. All SS of primary origin and pulmonary metastasis had already been diagnosed using SS18 break-apart FISH. The age at the identification of the primary tumor as SS was considered for each patient. In all 5 patients with SS, at least two metachronous metastasectomies were performed. The duration between the resection of primary sites and pulmonary metastasectomies ranged from 28 to 108 months. Cases 1, 3, 4, and 5 were monophasic spindle cell types, and Case 2 was biphasic type.
Table 1
Characteristics of the five patients with synovial sarcoma who underwent pulmonary metastasectomy.
Case no. | Age, years | Sex | Primary | State | Type | 1st | 2nd | 3rd | 4th | 5th |
1 | 63 | F | Ankle | Dead | Monophasic | Left wedge resection (1) | Right wedge resection (2) | Left wedge resection (1) | | |
| | | | | | 39 months | 59 months | 61 months | | |
2 | 28 | M | Mediastinum | Alive | Biphasic | Right lower lobectomy (1) | Left wedge resection + chest wall resection | | | |
| | | | | | 108 months | 177 months | | | |
3 | 33 | M | Forearm | Alive | Monophasic | Right basal segmentectomy (1) | Left wedge resection (1) | Left basal segmentectomy (1) | Left wedge resection (1) | |
| | | | | | 48 months | 63 months | 82 months | 100 months | |
4 | 51 | M | Knee | Alive | Monophasic | Right wedge resection (2) | Left wedge resection (2) | Right wedge resection (1) | Left wedge resection (1) | Right wedge resection (1) |
| | | | | | 28 months | 59 months | 76 months | 97 months | 108 months |
5 | 30 | M | Forearm | Alive | Monophasic | Right wedge resection (3) | Left wedge resection (2) | Right wedge resection (2) | Left wedge resection (3) | |
| | | | | | 32 months | 34 months | 68 months | 107 months | |
The age at which the primary tumor was identified as SS was considered for each patient. The months listed below the operative procedure indicates the duration since the identification of the primary origin. The number in parentheses next to the surgical procedure indicates the number of resected tumors. |
In Case 1, a 63-year-old woman with primary SS in the left ankle underwent pulmonary metastasectomy three times (left-sided wedge resection ×1 at 39 months after primary surgery followed by right-sided wedge resection ×2 at 59 months, and left-sided wedge resection ×1 at 61 months). The patient finally developed right-sided pleural dissemination and died of SS. IHC of SS18-SSX for pulmonary metastases was obtained from the first and second metastasectomy specimens. Figure 1A shows the computed tomographic findings of solitary pulmonary metastasis in the left lower lobe before the initial left wedge resection in this case.
In Case 2, a 28-year-old man had primary SS in the mediastinum. The large mass (60×60×40 mm) was protruding from the left side chest cavity (Fig. 2A, 2B), which was resected with combined pericardial resection by median sternotomy. The patients underwent metastasectomy twice (right lower lobectomy at 108 months after the primary surgery followed by left-sided chest wall resection with combined pulmonary wedge resection at 177 months). In this case, the definitive diagnosis of SS was not reached until the initial metastasectomy, which was 108 months after the primary surgery when SS was finally diagnosed through comprehensive pathology workups including SS18 break-apart FISH for primary and metastatic sites. Figure 2C shows FISH for SS18 rearrangement in the primary tissue, demonstrating a disconnected SS18 gene. No evidence of recurrence was observed 17 months after the last pulmonary metastasectomy.
Figure 2Computed tomography (CT) scan showing the results of fluorescence in situ hybridization for SS18 rearrangement and the results of immunostaining of SS18-SSX antibody in Case 2. (A)(B) The chest CT scan shows a mediastinal mass of size 60×60×40 mm. (C) Image showing the results of fluorescence in situ hybridization for SS18 rearrangement. A disconnected SS18 gene can be seen. (D) The SS18-SSX fusion-specific antibody (E9X9V) is positive.</fig>
In Case 3, a 33-year-old man with primary SS in the left forearm underwent pulmonary metastasectomy four times (right-sided basal segmentectomy at 48 months after the primary surgery followed by left-sided wedge resection ×1 at 63 months, left-sided basal segmentectomy at 83 months, and left-sided wedge resection ×1) and subsequent radiation therapy for right-sided pulmonary metastasis. Figure 1B shows the computed tomographic findings of the solitary pulmonary metastasis in the left lower lobe before left basal segmentectomy. IHC of SS18-SSX for pulmonary metastases was obtained from the first and second metastasectomy specimens. No evidence of recurrence was observed 2 months after the last pulmonary metastasectomy.
In Case 4, a 51-year-old man had the primary origin as the left knee. He underwent pulmonary metastasectomy five times (right-sided wedge resection ×2, left-sided wedge resection ×2, right-sided wedge resection ×1, left-sided wedge resection ×1 and right-sided wedge resection ×1). The patient was followed up without any treatment. IHC of SS18-SSX for pulmonary metastases was obtained from the third and fourth metastasectomy specimens. No evidence of recurrence was observed 10 months after the last pulmonary metastasectomy.
In Case 5, a 30-year-old man had the primary origin as the right forearm. He underwent pulmonary metastasectomies four times (right-sided wedge resection ×3, left-sided wedge resection ×2, right-sided wedge resection ×2 and left-sided wedge resection ×3). IHC of SS18-SSX for pulmonary metastases was obtained from the second and third metastasectomy specimens. He had recurrence and was undergoing chemotherapy.
IHC
Figure 3 shows the histologic findings of SS18-SSX IHC and hematoxylin and eosin of 10 pulmonary metastatic SS and 5 corresponding primary sites from 5 patients with SS. The SS18-SSX fusion-specific antibody was positive with diffusely strong staining in all 10 metastatic SS samples. All five primary SS tumors were stained similarly to the corresponding metastatic SS. However, no staining of SS18-SSX was observed in the 93 clinical and histologic mimics (49 other bone and soft tissue sarcomas, 39 primary lung cancers, and 5 SFTs). Figure 4 shows the histologic findings of SS18-SSX IHC of 15 representative cases from 93 clinical and histological mimics. A summary of the IHC results is presented in Table 2.
Table 2
Summary of the results of IHC staining for SS18-SSX antibody.
| Number | SS18-SSX-positive ratio |
Synovial sarcoma (metastasis) | 10 | 100% |
Synovial sarcoma (primary) | 5 | 100% |
Non-SS pulmonary metastatic tumors | | |
Osteosarcoma | 8 | 0% |
Chondrosarcoma | 7 | 0% |
Liposarcoma | 5 | 0% |
Malignant fibrous histiocytoma | 9 | 0% |
Ewing’s sarcoma | 4 | 0% |
Leiomyosarcoma | 9 | 0% |
Fibrosarcoma | 3 | 0% |
Undifferentiated sarcoma | 4 | 0% |
Primary lung cancer | | |
Adenocarcinoma | 9 | 0% |
Squamous cell carcinoma | 5 | 0% |
Small cell lung cancer | 4 | 0% |
Large cell lung cancer | 5 | 0% |
Pleomorphic carcinoma | 8 | 0% |
Carcinoid | 8 | 0% |
Solitary fibrous tumor | 5 | 0% |
IHC: immunohistochemistry; SS: synovial sarcoma |
Figure 5A shows the histologic finding of SS18-SSX IHC of a percutaneous needle biopsy specimen from the primary right forearm tumor in Case 5, demonstrating diffuse strong staining of SS18-SSX antibody similar to the surgically resected specimen (Fig. 3T). Figure 5B shows the cytological findings of SS18-SSX IHC of intraoperative touch imprint cytology specimen from the pulmonary metastatic site, demonstrating strong staining of the SS18-SSX antibody.
Figure 5Findings of immunostaining of SS18-SSX in the synovial sarcoma obtained by percutaneous biopsy in Case 5 (A) and intraoperative sealed cytology in Case 3 (B). The image shows strong diffuse nuclear staining.</fig>