Primary mediastinal sarcoma presenting with supraclavicular and chest wall metastasis

INTRODUCTION

Primary mediastinal sarcomas (PMS) are extremely uncommon cancerous tumors of mesenchymal origin, which constitute from 2% to 8% of all malignant mediastinal tumors and 1.4% of adult soft-tissue sarcomas.^[1,2] PMS tumors are often seen in young males and are often large, with proximity to vital structures of the mediastinum. The symptoms are often vague or result from the pressure exerted on, or invasion of, adjacent structures. Computed tomography (CT) features may not be pathognomonic as these tumors have highly varied presentations, but they may help in the assessment of invasion, metastasis, and planning for surgical resection. Diagnosing these tumors can be challenging, with immunohistochemistry (IHC) being crucial for their classification. There is a paucity of understanding of treatment outcomes in patients with mediastinal sarcoma, and most authors recommend a multidisciplinary approach with complete resection being advocated as far as possible, along with chemotherapy/radiation.^[3,4]

CASE REPORT

A 35-year-old male, with no comorbidities, presented with a 30-day history of cough associated with expectoration. The cough was gradually progressive and accompanied by exertional dyspnea. In addition, the patient reported a painless swelling in the right supraclavicular region for the past month and a right-sided chest wall swelling for the past 3 weeks. He also experienced significant, unintentional weight loss of approximately 10 kg during this period. He had no history of fever, smoking, or prior pulmonary tuberculosis.

General examination revealed multiple cervical lymph nodes, which were firm, non-tender, and non-mobile swellings measuring 5 × 3 cm in the right supraclavicular region [Figure 1]. There was no pallor, icterus, cyanosis, clubbing, or pedal edema. Another swelling, hard in consistency and non-mobile, measuring 4 × 4 cm, was noted in the right parasternal region. His oxygen saturation (SpO₂) was recorded at 84% on room air, while other vital parameters were within normal limits.

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Figure 1:

Swelling in the neck and chest wall (red arrows).

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Radiogram of the chest depicted a right upper to mid-zone parasternal opacity along with deviation of the trachea toward the left side, suggestive of a space-occupying lesion [Figure 2].

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Figure 2:

Chest X-ray showing right upper to mid-zone parasternal opacity along with deviation of the trachea toward the left side (red arrow).

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Laboratory investigations showed a hemoglobin level of 15.0 g/dL, and the total white blood cell count was significantly raised at 21,060/mL, indicating leukocytosis. The differential count revealed neutrophilia (86.8%), with decreased lymphocytes (4.8%) and minor elevations in eosinophils (2.9%) and monocytes (5.5%).

A contrast-enhanced whole-body CT scan revealed several important findings. Bilateral level Ib submandibular lymph nodes appeared reactive in nature, while enlarged cervical lymph nodes (levels II to IV) were seen bilaterally, measuring up to 5.5 cm [Figure 3a]. A large, conglomerate nodal mass measuring 7.9 × 5.8 cm was identified in the anterior mediastinum extending to the anterior chest wall [Figure 3b and c]. This mass showed encasement of the superior vena cava and contiguous extension into the right anterior chest wall. A small pulmonary nodule (3 mm) was noted in the middle lobe of the lung. In addition, there were enlarged paratracheal and subcarinal lymph nodes (1–3 cm), narrowing of the right main bronchus, and a small pericardial effusion. These radiological findings raised a strong suspicion of metastatic disease, likely originating from a pulmonary primary.

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Figure 3:

(a) computed tomography (CT) image showing enlarged cervical lymph nodes (red arrow), (b) CT image showing mediastinal mass and narrowing of right main bronchus (red arrow), (c) CT image showing anterior chest wall swelling in continuum with mediastinal mass (red arrow).

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Fine-needle aspiration cytology of the right supraclavicular mass showed cellular features consistent with malignancy. The smears demonstrated round to oval and elongated cells with scant to moderate cytoplasm, oval nuclei with prominent nucleoli, and occasional large uni- and binucleate cells amidst a background of inflammatory cells. A subsequent ultrasound-guided core biopsy confirmed the presence of highly pleomorphic atypical cells with eosinophilic cytoplasm and hyperchromatic nuclei, along with evidence of atypical mitotic activity and a dense inflammatory infiltrate composed of eosinophils, neutrophils, and lymphocytes [Figure 4].

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Figure 4:

Hematoxylin and eosin staining of biopsy specimen showing highly pleomorphic atypical cells with eosinophilic cytoplasm and hyperchromatic nuclei, along with evidence of atypical mitotic activity (red circle).

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Immunohistochemical staining was performed for further classification. The tumor cells were positive for Vimentin, indicating mesenchymal origin, and negative for cytokeratin and cluster of differentiation 45, effectively ruling out epithelial and hematopoietic malignancies, respectively [Figure 5]. These results were indicative of sarcoma, most likely of mediastinal origin, with metastatic involvement.

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Figure 5:

Immunohistochemical staining showing negative for Cytokeratin (CK), negative for CD4, and positive for Vimentin.

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The patient was referred to a higher center for detailed oncological evaluation and treatment, including staging work-up and formulation of an appropriate treatment plan.

DISCUSSION

Primary sarcomas arising from the mediastinum are uncommon. Mediastinal sarcomas are rare and diverse tumors, resulting in limited data available in the literature, with most information derived from case reports or institutional series.^[1,4-6] Unlike sarcomas found in the extremities or superficial soft tissues, mediastinal sarcomas often remain asymptomatic until they grow to a significant size. These tumors present distinct challenges related to accurate histological diagnosis, determination of the primary origin, and treatment planning. They predominantly occur in young adults, with a slight preference for males.^[1] Although imaging findings are generally nonspecific, they typically show a large, heterogeneous mass situated in either the anterior or posterior mediastinum. Diagnosis is made by Histo-pathological examination of the biopsy specimen. IHC is required for confirmation of diagnosis and classification of the tumor. Complete surgical resection is advocated, which may not be possible in two-thirds of the cases because of neighboring structure invasion. The role of neoadjuvant chemotherapy or radiation therapy is doubtful and may be used to reduce the tumor size before surgery.

CONCLUSION

PMS are rare, aggressive tumors with complex diagnosis and management due to their heterogeneity and critical location. Imaging guides resectability, but diagnosis relies on histopathology and IHC. Surgery is the mainstay, though complete resection is often limited by vital structures. Multidisciplinary treatment is essential, and multicenter studies are needed to standardize care and improve outcomes.