Primary Pulmonary Synovial Sarcoma, a high complexity case in a young male adult.

A 26-year-old man, cigarette smoker with no relevant medical history, presented to hospital emergency unit  for fever, cough mild-productive for 2 weeks and right chest pain.

Chest X-ray showed opacification of the lower third right lung with pleural effusion. Ultrasonography showed a solid mass with anechoic areas inside. A contrast-enhanced Computed Tomography confirmed a large heterogeneous density lesion, neither obstructing nor infiltrating the right stem bronchus, a small amount of pleural effusion and no mediastinal and axillary lymphadenopathies. The US-guided fine-needle biopsy result was: “epitheliomorphic neoplasm with a rabdoid component, not necrosis, mitotic index up to 5 mitosis/10HPF. CD56 positivity with the relatively low proliferation index is compatible with neuroendocrine neoplasm”. PET-CT  showed pathological expression of somatostatin receptors, compatible with neuroendocrine pathology in cohesistence with an undifferentiated component. A second biopsy, aimed to detect genetic alterations for targeted therapy, found ASXL1 G967 del – CTNNA1 loss. The control CECT showed enlargement of the lesion. A new biopsy revealed a spindle cell malignant mesenchymal neoplasm with morphological and immunophenotypic characters consistent with the diagnosis of monophasic synovial sarcoma.

Synovial sarcoma is a malignant tumour affecting primarily young adults and can hit any anatomic site[1]. Primary Pulmonary synovial sarcoma (PPSS) is very rare, accounting for less than 0,5% of all lung tumours [2]. It may originate from lung parenchyma, bronchial tree or pulmonary arteries; it is supposed to originate from the pluripotent mesenchymal cells in the pulmonary system [3].

Most patients are asymptomatic at presentation. Anyway, when symptoms arise, they are aspecific, the most common being cough, chest pain, hemoptysis and an enlarging pleural-based mass [4].

PPSS diagnosis relies on clinical manifestations, imaging, histopathology and immunochemistry. There is a knowledge gap for early recognition, and physicians cannot foresee the tumor pattern [6].

Tumours appear well circumscribed ranging within 0,6-31 cm, with or without a capsule. Histologically, the monophasic spindle cell type is the most common pattern [7].

Clinically PPSS cannot be differentiated from other tumours, and cytology, especially in enormous pulmonary sarcomas, might not be exhaustive [8]. Cytogenetic analysis can detect the translocation t(X; 18) (p11.2;q11.2) which leads to SS18 (formerly SYT)-SSX gene fusion which characterizes synovial sarcoma [5,6,7,8].

The prognosis of PPSS is very poor and depends on tumour size (>5 cm), sex (male>female), age (>20y), extension of necrosis, mitotic rate (more than 10 mitotic figures/10 high-power fields), neurovascular invasion, and presence of SYT-SSX1 gene fusion [5,9]. Currently, there is no standardized therapy for PPSS and the primary treatment approach is wide surgical excision with removal of the tumour with free surgical margins and possible radiotherapy if deemed helpful [1]. Unfortunately, surgical excision is not always possible, depending on the tumour size.

In advanced or unresectable tumours, doxorubicin- and ifosfamide-based chemotherapy gives an overall rate response of around 24% [10,11]. However, the efficacy of chemotherapy is still controversial and improves survival only in high-risk patients [12]. PPSS is very malignant, with the 5-year overall survival significantly worse than soft tissue sarcomas of the extremities (35% versus 71%) [13].

All patient data have been completely anonymised throughout the entire manuscript and related files.

Take Home Message / Teaching Points

Primary pulmonary synovial sarcoma is a very rare tumour that appears as a mass on chest X-ray and Computed Tomography and whose diagnosis relies on histologic analysis and immunostaining,