Primary Thoracic Sarcoma in a 61-Year-Old Woman: A Rare but Aggressive Mediastinal Tumor

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 Primary Thoracic Sarcoma in a 61-Year-Old Woman: A Rare but Aggressive Mediastinal Tumor

Keywords: primary thoracic sarcoma, mediastinal mass, spindle cell sarcoma, FDG-PET CT, anterior mediastinal tumor, thoracic oncology, chest CT, pleural effusion, malignant mediastinal mass

Introduction

Primary thoracic sarcomas are exceedingly rare neoplasms that often masquerade as more common mediastinal masses. When they occur in the anterior mediastinum, they challenge even experienced radiologists and oncologists due to their heterogeneous imaging appearance and aggressive local behavior. This column presents a case study of a 61-year-old woman with worsening dyspnea, ultimately diagnosed with a primary thoracic sarcoma—specifically, a spindle cell sarcoma—through radiological evaluation and core needle biopsy.

Clinical Presentation

A 61-year-old woman presented with progressively worsening shortness of breath over the past two weeks. She initially visited her outpatient clinic for a routine chest X-ray, but due to concerning radiographic findings, she was referred to the emergency department for further evaluation and imaging.

Imaging Evaluation

[Figure 1] Chest Radiographs: A-P and Lateral Views

Initial chest radiographs revealed a large left-sided pleural effusion and rightward mediastinal shift, indicative of significant mass effect and possible underlying malignancy.

[Figure 2] Chest CT – Axial Plane

Contrast-enhanced axial CT demonstrated an 8 cm heterogeneous soft tissue mass in the left anterior mediastinum, showing lobulated margins and invasion into adjacent anterior chest wall structures, including the sternum.


[Figure 3] Chest CT – Sagittal Plane

Sagittal reconstruction confirmed sternal erosion and anterior mediastinal expansion of the lobulated mass.


[Figure 4] F-18 FDG PET-CT

PET-CT revealed the mediastinal mass to be highly FDG-avid, suggesting aggressive metabolic activity. No evidence of distant metastasis was observed. Complete left lung atelectasis and large left pleural effusion were also noted.


Key Findings

  • Mass characteristics: Heterogeneous, lobulated soft tissue mass measuring up to 8 cm in the anterior mediastinum.

  • Invasiveness: Sternal erosion, chest wall invasion, and complete left lung atelectasis.

  • Metabolic activity: High FDG avidity on PET-CT.

  • Pleural findings: Massive left pleural effusion with contralateral mediastinal shift.

Differential Diagnosis

Mediastinal masses have a broad differential, often summarized by the mnemonic 4 Ts:

  • Thymoma

  • Teratoma

  • Thyroid/parathyroid neoplasm

  • Terrible lymphoma

However, rare entities such as primary thoracic sarcomas must also be considered, especially in the presence of aggressive radiologic features. The differentials in this case included:

  1. Teratoma

  2. Thymoma

  3. Thyroid/parathyroid neoplasm

  4. Lymphoma

  5. Primary thoracic sarcoma

  6. Hemangioma

  7. Lipoma

  8. Metastasis

Final Diagnosis

Primary Thoracic Sarcoma – Spindle Cell Sarcoma

Histopathological evaluation following core needle biopsy confirmed the diagnosis of spindle cell sarcoma, a rare subtype of mesenchymal tumors originating in the thorax.

Discussion

Pathophysiology

Thoracic sarcomas originate from mesenchymal stem cells and encompass a wide range of histologic subtypes, including vascular, adipocytic, fibrous, and neurogenic tumors. Spindle cell sarcomas, characterized histologically by elongated fusiform cells arranged in fascicles, are particularly rare in the anterior mediastinum.

Imaging Characteristics

Sarcomas in the chest often present as heterogeneous masses with variable contrast enhancement and aggressive invasion into nearby structures. In this case, radiologic hallmarks included:

  • Sternal erosion

  • Mediastinal shift due to large effusion

  • Atelectasis of the ipsilateral lung

  • FDG avidity on PET-CT

These findings collectively point toward a malignant process and help in narrowing the differential diagnosis.

Clinical Course

Sarcomas often remain undetected until they produce mass effect or invade nearby structures. Symptoms may include chest pain, cough, or dyspnea. In some cases, patients remain asymptomatic, and the tumors are found incidentally.

Histopathological Correlation

Definitive diagnosis requires histological confirmation. Spindle cell sarcomas show elongated, uniform cells with mitotic activity. Immunohistochemistry may help differentiate it from other spindle cell lesions.

Treatment and Prognosis

Surgical resection remains the mainstay of treatment for localized thoracic sarcomas. The prognosis depends on the histologic subtype, tumor size, extent of local invasion, and completeness of resection. Radiation and chemotherapy may be considered based on pathological findings and resectability. Recurrence is common, and long-term follow-up is essential.

Quiz

1. What is the most prominent finding on the chest CT?

  1. A large heterogeneous soft tissue mass in the anterior mediastinum with sternal erosion

  2. A large soft tissue mass encasing the trachea and aortic arch

  3. A posterior mediastinal mass invading the vertebral body and posterior ribs

  4. An irregular right breast mass with scattered calcifications


2. What is the key finding on the chest radiograph?

  1. Large left pleural effusion

  2. Large right pleural effusion

  3. Mediastinal shift to the right

  4. Mediastinal shift to the left

  5. Large left pleural effusion with rightward mediastinal shift

  6. Large right pleural effusion with leftward mediastinal shift


3. What is the FDG avidity of the mediastinal mass on PET-CT?

  1. FDG avid

  2. FDG non-avid

  3. FDG uptake indeterminate


4.  Do the imaging features suggest a benign or malignant cause?

  1. Malignant

  2. Benign


5.  Which of the following are part of the differential diagnosis for an anterior mediastinal mass?

  1. Teratoma

  2. Thymoma

  3. Thyroid/parathyroid neoplasm

  4. Lymphoma

  5. Primary thoracic sarcoma

  6. Hemangioma

  7. Lipoma

  8. Metastasis

  9. All of the above


6. What is the definitive diagnostic step for confirming the nature of the mediastinal mass?

  1. Empiric chemotherapy

  2. Bronchoscopy

  3. CT follow-up in 3 months

  4. Core needle biopsy and histopathological analysis

Answer & Explanation

1. Answer: 1, Explanation: Contrast-enhanced CT shows a large lobulated soft tissue mass in the anterior mediastinum, causing sternal erosion and anterior chest wall invasion. This is the key radiologic indicator of malignancy.

2. Answer: 5, Explanation: The chest radiograph shows massive left pleural effusion, which has shifted the mediastinum to the right. This finding suggests a significant mass effect from a space-occupying lesion in the left hemithorax.

3. Answer: 1, Explanation: The F-18 FDG PET-CT demonstrates high FDG uptake in the mediastinal mass, indicating high metabolic activity, which is consistent with malignancy, particularly sarcoma.

4. Answer: 1, Explanation: Findings such as sternal erosion, invasion of soft tissues, pleural effusion, and FDG avidity all point toward malignancy, which in this case is confirmed as a spindle cell sarcoma.

5. Answer: 9, Explanation: The differential for anterior mediastinal masses includes both common tumors (4Ts) and rare tumors like sarcoma. The correct approach is to include all possibilities, especially when aggressive features are seen.

6. Answer: 4, Explanation: While imaging is essential for initial evaluation, definitive diagnosis requires tissue sampling. A core needle biopsy provides histological confirmation—in this case, spindle cell sarcoma.

Conclusion

This case underscores the importance of considering primary thoracic sarcoma in the differential diagnosis of anterior mediastinal masses, especially when radiological features indicate aggressive behavior. Early recognition through imaging and timely tissue diagnosis are essential for management. Despite being rare, thoracic sarcomas carry a poor prognosis and demand multidisciplinary care for optimal outcomes.

References

[1] G. W. Gladish, B. M. Sabloff, R. F. Munden, M. T. Truong, J. J. Erasmus, and M. H. Chasen, “Primary thoracic sarcomas,” Radiographics, vol. 22, no. 3, pp. 621–637, 2002.

[2] P. Stark, C. D. Eber, and F. Jacobson, “Primary intrathoracic malignant mesenchymal tumors: pictorial essay,” J. Thorac. Imaging, vol. 9, no. 3, pp. 148–155, 1994.

[3] D. Suster, “Spindle cell tumors of the mediastinum,” Ann. Diagn. Pathol., vol. 60, p. 152018, 2022.

[4] J. D. Rushing, L. G. Loehrer, and S. J. Loehrer, “Sarcomas of the mediastinum: current concepts and management,” Oncologist, vol. 25, no. 4, pp. 251–258, 2020.

[5] A. E. Rosado-de-Christenson and C. Galobardes, “Tumors of the mediastinum,” Semin. Roentgenol., vol. 34, no. 1, pp. 36–51, 1999.

[6] M. L. Webb, J. R. Sawyer, and J. L. Lewis, “A rare case of mediastinal spindle cell sarcoma,” Ann. Thorac. Surg., vol. 102, no. 3, pp. e229–e231, 2016.

[7] J. F. Gibbs and J. T. Huang, “Management of primary chest wall tumors,” Surg. Clin. North Am., vol. 80, no. 3, pp. 1035–1049, 2000.

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