Case of the Month: August, 2012, Page 4

Case Summary:

  • 46-year-old male with a distant history of follicular non-Hodgkin's lymphoma status post allogenic stem cell transplant and chronic graft versus host disease presented with several months of increasing shortness of breath and left chest wall pain and muscle spasms to outside PCP. An outside chest radiograph he had brought with him showed a 24 x 12cm left chest mass that was not present on the most recent radiograph 11 months prior.
  • CT with contrast showed a 20.3 x 17.1 x 12.7 cm left hemithorax mass involving the anterior mediastinum with intimate association with the vessels of the superior mediastinum and left hilum, abutment of the left cardiac margin, effacement of the left main bronchus, and near total atelectasis of the left upper lobe and superior segment left lower lobe. Subsequent left anterior mediastinoscopic biopsy of the mass was consistent with spindle cell rhabdomyosarcoma, grade 3.
  • Patient was discharged for outpatient management but readmitted 3 weeks later with worsening symptoms. Chest MRI/MRA showed significant interval increase in size of mass now measuring 28 x 20 x 17 cm with total collapse of left lung, marked narrowing of the left main pulmonary artery and minimal perfusion of the left lung, increased mass effect on mediastinum and inferior displacement of left hemidiaphragm, encasement of great vessels at aortic arch, and occlusion of the left brachiocephalic vein. Resection of the mass and left pneumonectomy was performed. Subsequent pathology was consistent with a malignant solitary fibrous tumor of the pleura with high grade myosarcomatous and fibrosarcomatous transformation.

Localized Fibrous Tumor of the Pleura:

  • Most commonly involves the inferior hemithorax although occasionally found in the mediastinum, lung, heart, or pericardium and less commonly extrathoracic. There is a slight female predominance and the majority of cases occur in the 6th and 7th decades.
  • LFTP is a mesenchymal tumor most often presenting as a solitary lesion arising from the visceral pleura. About half are pedunculated although adhesions to the adjacent parietal pleura and pericardium are common. They are generally smooth, well-circumscribed masses with variegated cut surfaces that often have a whorled or nodular pattern and malignant lesions are more likely to have areas of cystic change, hemorrhage, and necrosis. Histologically they appear as low-grade neoplasms with ovoid to spindle-shaped cells, round to oval nuclei, and faintly cytoplasmic nuclei. Microscopic architecture is most commonly the "patternless pattern" with tumor cells and collagen arranged in a random fashion. Immunohistochemistry and electron microscopy have helped to reveal that these lesions are distinct from the more common primary pleural tumor mesothelioma. They have been shown to express vimentin (a marker of mesenchymal cells) and CD34 (a transmembrane cell-surface glycoprotein universally found in dendritic interstitial cells).
  • All imaging modalities classically demonstrate a well-defined, lobular, non-invasive, solitary nodule or mass that abuts the pleural surface. They are reported to occur more commonly in the mid and inferior hemithorax. On radiography some of the margins may be well-defined while the pleural based margins are obscured. The lesions most often grow slowly but depending on their histologic grade growth rates may be rapid.
  • On CT small lesions tend to be homogeneous and may form obtuse angles with the pleura suggestive of their pleural origin. Larger lesions tend to be more heterogeneous and are more likely to have acute angles with the pleura making their pleural origin more difficult to ascertain. Uncommonly, a pedicle may be visualized or indirectly surmised based on observed mobility of the mass. Mass effect on the lung and mediastinum is more common with malignant subtypes and some lesions may arise within the mediastinum itself. Calcification may occur. Lymphadenopathy is not associated. Enhancement is typical and depending on the amount of necrosis, hemorrhage, or cystic change may be more or less heterogeneous.
  • Complete surgical excision is the treatment of choice and adjuvant chemotherapy likely has little benefit due to the low grade of most tumors. Long-term imaging follow-up and excision of any recurrent or metastatic disease is necessary.

 

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