Solitary primary pulmonary synovial sarcoma: A case report

Abstract

Background: Synovial sarcoma (SS) is an uncommon and highly malignant soft tissue sarcoma in the clinic, with primary pulmonary SS (PPSS) being extremely rare. Here, we describe the clinical characteristics, diagnosis, and treatment of a solitary PPSS case confirmed via surgical resection and fluorescence in situ hybridization (FISH).

Case summary: A 33-year-old man was admitted because of intermittent coughing and hemoptysis for one month, with lung shadows observed for two years. Whole-body positron emission tomography-computed tomography (PET-CT) revealed a solitary mass in the upper lobe of the right lung, with uneven radioactivity uptake and a maximum standardized uptake value of 5.6. The greyish-yellow specimen obtained following thoracoscopic resection was covered with small multi-nodulated structures and consisted of soft tissue. Hematoxylin and eosin staining revealed spindle-shaped malignant tumor cells. Immunohistochemistry indicated these tumor cells were CD99 and BCL-2-positive. Furthermore, the FISH test revealed synovial sarcoma translocation genetic reassortment, which confirmed the diagnosis of SS.

Conclusion: PPSS is extremely rare and tends to be misdiagnosed as many primary pulmonary diseases. PET-CT, histologic analysis, and FISH tests can be used to differentiate PPSS from other diseases. Surgical resection is regularly recommended for the treatment of solitary PPSS and is helpful for improving the prognosis.

Keywords: Case report; Fluorescence in situ hybridization; Positron emission tomography-computed tomography; Primary pulmonary synovial sarcoma; Solitary pulmonary nodule; Spindle cells; Synovial sarcoma translocation.

Figure 1

Computed tomography scans of the chest. A and B: The shadow of the round nodules in the upper lobe of the right lung was detected in 2018, with a maximum diameter of about 14 mm and smooth edges; C and D: In 2019, the detected lesion had grown significantly larger, reaching a maximum diameter of approximately 30 mm, with smooth edges and shallow lobes (white arrows); E and F: By 2020, the lesion had grown to approximately 20 mm × 34 mm × 42 mm in size, with irregular density, smooth edges spotted with calcifications, slightly shallow lobes (white arrows), an uneven level of enhancement, and a ring-shaped enhanced image around the perimeter (orange arrow); G and H: From postoperative to 2021, no shadows with an abnormally high density were observed.

Figure 2

Positron emission tomography-computed tomography scan. A-D: Showed a solitary round mass in the upper lobe of the right lung, with unevenly increased radioactivity uptake and an SUVmax of 5.6; E and F: Fiberoptic bronchoscopy revealed the presence of new organisms (white arrows) at the posterior opening of the upper right lobe, with a smooth capsule, surrounded by purulent secretions, and oozing a small amount of blood; G: The specimen obtained following the thoracoscopic resection of the posterior segment of the right upper lobe of the lung was grayish yellow in color, with some small round-like changes and a soft texture.

Figure 3

Hematoxylin and eosin staining. A: Hematoxylin and eosin (H&E) staining of tissue sections of posterior segment of the right lung upper lobe obtained from surgery (H&E 200×). The tumor was composed of spindle cells, which were arranged in dense cellular sheets or vague fascicles, with a herringbone architectural pattern; B-F Immunohistochemistry (IHC) revealed the tumor cells were diffusely positive for BCL-2 (B) and CD99 (C), and negative for CD34 (D), EMA (E) and TLE1 (F). The blood vessels inside the tumor showed positive staining for CD99 (C) (IHC 200×); G: Fluorescence in situ hybridization analyses: Red and green signals show break-apart regions (white arrows), representing the splitting of SS18 (synovial sarcoma translocation, SYT).