SS is a malignant tumor characterized by slow, painless, and well-defined masses. Despite its benign appearance, SS exhibits high invasiveness [4]. Named for its histological resemblance to synovial tissue, SS rarely involves synovial structures and is believed to originate from multipotent mesenchymal cells [5]. SS presents with a low incidence, with a higher prevalence in males (male-to-female ratio approximately 1.2:1), typically affecting individuals aged 17 to 67, with a peak occurrence in young adults aged 15 to 40 years. While more frequently observed in the lower limbs, SS of the head and neck is rare, accounting for only 3%-10% of all SS cases [6–7]. In the head and neck region, the parapharyngeal space stands out as the most affected site [8]. The slow growth of head and neck SS, combined with the intricate organ structures in this region, frequently leads to delayed detection, resulting in presentations characterized by local invasion, compression symptoms, or enlarged neck lymph nodes. The primary symptom typically involves a painful mass, accompanied by additional site-specific manifestations such as hoarseness, dysphagia, or bleeding [9]. In this case, the male patient presented with a lesion primarily in the pharynx, seeking medical attention due to local pain, dysphagia, and enlarged neck lymph nodes—typical clinical features of this disease.
Imaging studies, such as computed tomography (CT) and MRI, play a crucial role in determining the location, size, calcification, and infiltration of adjacent organs. CT scans are effective for evaluating SS in the head and neck, typically revealing well-defined, homogeneous lesions with infrequent multifocal involvement. While not diagnostic in isolation, MRI provides enhanced soft tissue contrast, aiding in the detailed assessment of tumor size, morphology, location, and extent of invasion. MRI also elucidates surrounding vascular and neural structures, thereby facilitating surgical planning. However, due to the nonspecific nature of clinical symptoms and imaging findings, SS diagnosis remains challenging and is often initially misdiagnosed. The gold standard for diagnosis is histopathological examination, where SS typically displays spindle cell histology. Depending on epithelial differentiation, SS can be classified into several subtypes: biphasic (comprising epithelial and spindle cell components), monophasic spindle cell, monophasic epithelial, or poorly differentiated forms [7]. A characteristic chromosomal translocation, t(X;18) (p11.2; q11.2), that results in the fusion of the SS18 (SYT) gene on chromosome 18 with the SSX gene on the X chromosome, is a diagnostic marker for synovial sarcoma (SS) in clinical practice. Additionally, immunohistochemical markers like TLE1 have shown promising diagnostic value. For patients where surgical options are limited, fine-needle aspiration biopsy (FNA) offers high sensitivity and specificity in assessing soft tissue lesions. In this case, the patient tested positive for several markers including AE1/AE3, Vimentin, TLE1, CAM5.2, CD99, EMA, and CK7, corroborating the diagnosis of biphasic synovial sarcoma.
Given the rarity of head and neck SS, there is currently no standardized treatment protocol. Previous reported modalities include surgical resection, radiotherapy, and chemotherapy. Among these, surgical excision with clear margins remains the primary treatment objective, involving complete or partial tumor removal, neck lymph node dissection, and flap reconstruction as warranted by factors such as tumor size, location, depth, and extent of infiltration [11]. However, due to the intricate anatomy of the head and neck region, achieving curative surgery can be challenging, often resulting in high rates of postoperative recurrence. Consequently, high-risk patients often necessitate additional radiotherapy and chemotherapy to enhance local control and diminish the likelihood of distant metastasis. Postoperative radiotherapy has been shown to improve the prognosis for patients with tumors located in the head and neck, particularly in cases with positive surgical margins. It has demonstrated efficacy in improving local control and overall survival. The recommended radiation therapy dose usually falls within the range of 65–70 Gy. However, the necessity for adjuvant radiotherapy in cases with adequate margins remains a topic of debate [12].
Limited experience exists with adjuvant chemotherapy, with a regimen combining ifosfamide and pirarubicin being endorsed by several experts [13–15]. Meta-analyses focusing on sarcomas have suggested that adjuvant chemotherapy for locally resectable soft tissue sarcomas in adults can enhance the time to local and distant recurrence as well as overall disease-free survival. Hence, adjuvant chemotherapy holds promise in mitigating the risk of local recurrence and distant metastasis, rendering it a standard first-line treatment for high-risk patients [16]. With the growing significance of targeted therapy in contemporary oncology, highly specific chromosomal translocations may assume a pivotal role in future synovial sarcoma-specific treatments.
Compared to SS at other anatomical sites, head and neck SS exhibits a greater propensity for local invasion and distant metastasis, with the lungs being the most common site of metastasis [17]. Patients with tumors larger than 5 cm face an elevated risk of local recurrence, distant metastasis [17], and mortality compared to those with smaller tumors. Additional adverse prognostic factors include patient age (over 25 years), inadequate surgical margins, p53 mutations, high mitotic rate, and poor histological differentiation. Therefore, vigilant long-term follow-up, extending over at least a decade, is imperative for monitoring disease progression [18].
In the case discussed, extensive local invasion and multiple lymph node metastases characterized the patient's initial presentation. Despite the feasibility of surgical resection, the inability to preserve organ function precluded this option. Consequently, induction chemotherapy was initiated, aiming for tumor reduction, followed by curative radiotherapy and sequential chemotherapy. This approach underscores the need for comprehensive treatment strategies in cases where surgery is impractical. Although the treatment regimen was not completed due to concurrent medical issues, the patient's condition stabilized, highlighting the potential of non-surgical interventions in managing this disease effectively.
This case underscores the importance of documenting complex cases to enhance our understanding of head and neck SS. It challenges the conventional reliance on surgery, illustrating the potential of radiotherapy and chemotherapy as primary treatments when surgical resection is untenable. Such documentation not only provides clinical insights but also contributes to the broader oncological discourse, encouraging ongoing research into innovative treatment strategies tailored to the unique needs of patients with rare and complex cancers.