Biphasic synovial sarcoma with a striking morphological divergence from the main mass to lymph node metastasis

Abstract

Rationale: Synovial sarcoma accounts for 5% to 10% of all soft tissue sarcomas and involves almost any anatomic site, particularly the deep soft tissue of the extremities of young adults. The incidence rate of lymph node metastases in synovial sarcoma is 3% to 7%, but the detailed morphological features of the metastatic tumors in the lymph node have not been documented. Patient concerns: A 64-year-old Korean man presented with a huge mass in the left lower thorax and multiple hypermetabolic lymph nodes along the mediastinal, supraclavicular, internal mammary, and retrocrural regions. Diagnoses: The patient was diagnosed with primary pleuropulmonary biphasic synovial sarcoma with lymph node metastases, where the main mass mostly comprised spindle cells (>95%) and the metastatic lymph nodes comprised only epithelial cells. Interventions: Left lower lobe lobectomy with the resection of the chest wall (including left ribs 8-10) and diaphragm and mediastinal lymph node dissection were performed. Outcomes: In the 2-month follow-up period, there have been no complications so far, and the attending physician is currently planning for the adjuvant chemotherapy. Lessons: The main mass and the metastatic lesion can be clearly different morphologically. In tumors with biphasic differentiation, such as synovial sarcoma, cells that constitute only a small fraction of the main mass may appear as the dominant cells in metastatic lesions.

Synovial sarcoma: characteristics, challenges, and evolving therapeutic strategies

“… 30 Monophasic SS is most often composed of monomorphous spindle cells with moderate cytologic atypia organized in fascicles. 5 , 31 , 32 Biphasic tumors, in addition to a fascicular spindle cell component, feature a variably abundant epithelial component sometimes forming true glandular-like structures. 5 , 32 , 33 Poorly differentiated tumors contain areas of high cellularity and the tumor cells most often have a rounded morphology.…”

“… 5 , 31 , 32 Biphasic tumors, in addition to a fascicular spindle cell component, feature a variably abundant epithelial component sometimes forming true glandular-like structures. 5 , 32 , 33 Poorly differentiated tumors contain areas of high cellularity and the tumor cells most often have a rounded morphology. 5 , 32 , 34 The prognostic role of histological variants is yet to be fully elucidated.…”

“… 5 , 32 , 33 Poorly differentiated tumors contain areas of high cellularity and the tumor cells most often have a rounded morphology. 5 , 32 , 34 The prognostic role of histological variants is yet to be fully elucidated. 5 , 31 , 32 , 33 , 34 A multicenter, retrospective analysis showed high histologic grade [Fédération Nationale des Centres de Lutte Contre Le Cancer (FNCLCC) grade 3], high mitotic count (≥10 mitoses/10 high-power field), large tumor size (>7 cm), International Union Against Cancer (Union Internationale Contre le Cancer)(UICC)/tumour–node–metastasis (TNM) stage III disease, tumor necrosis, and the presence of poorly differentiated morphology as poor prognostic indicators in adults with SS.…”

“… 5 , 32 , 34 The prognostic role of histological variants is yet to be fully elucidated. 5 , 31 , 32 , 33 , 34 A multicenter, retrospective analysis showed high histologic grade [Fédération Nationale des Centres de Lutte Contre Le Cancer (FNCLCC) grade 3], high mitotic count (≥10 mitoses/10 high-power field), large tumor size (>7 cm), International Union Against Cancer (Union Internationale Contre le Cancer)(UICC)/tumour–node–metastasis (TNM) stage III disease, tumor necrosis, and the presence of poorly differentiated morphology as poor prognostic indicators in adults with SS. 35 Similarly, a single-center, retrospective case study of 196 patients found that OS was significantly worse in patients with either monophasic SS or grade 3 tumors.…”

Biphasic synovial sarcoma with squamous differentiation in the thigh – A case report

“…It may also present in trunk, head and neck, thorax, mediastinum, chest wall, lumbar spine, and heart. 3 These tumors present as palpable mass associated with the pain or tenderness. This tumor is classified histologically into biphasic, monophasic and poorly differentiated types.…”