53 years old male with progressive pulmonary thromboembolism despite anticoagulant therapy

Case provided by Vincent

History
A 53 years old melanoma patient was initially diagnosed with an incidental pulmonary thromboembolism. Despite therapeutic anticoagulation, pulmonary thromboembolism was progressive three months later.

Image findings
The initial CT scan performed for melanoma staging incidentally shows a central pulmonary thromboembolism pronounced on the right side in a staging CT scan (A, B). Three months later, pulmonary thromboembolism was progressive (C compared to B). A FDG PET-CT scan shows increased FDG-uptake within the thromboembolism (D).

Diagnosis
Pulmonary artery leiomyosarcoma (PAL).

Discussion
The incidence of primary malignant tumors of the pulmonary artery is very low (0,001-0,03%). PAL is an extremely rare type of primary sarcoma that typically originates form the intima of the pulmonary artery. There are at least 10 subtypes of pulmonary sarcomas. The first case of PAL was described in 1923 by Mandelstamm et al. The diagnosis often is difficult and delayed since the clinical presentation and results from enhanced CT scans might mimic PE. Therefore, and due to its low incidence, PAL often is misdiagnosed as PE or chronic thromboembolic pulmonary hypertension (CTEPH). PAL patients who are initially misdiagnosed with PE typically fail to respond to anticoagulant therapy. Hence, PAL is an important differential for persistent PE. In most cases, diagnosis is confirmed by histopathological analysis upon surgical resection or biopsy. FDG PET-CT scans are useful for differentiating between thromboembolisms and neoplasms. PAL has a poor prognosis. The only curative therapeutic option is immediate surgical resection upon early diagnosis. The average survival without surgical resection is about 18 months. So far, the effects of neoadjuvant or adjuvant chemo-/radiotherapies have not been sufficiently elucidated.

Teaching points

  • PAL is a rare primary sarcoma originating from the intima of the pulmonary artery
  • PAL is often misdiagnosed as pulmonary thromboembolism and patients typically fail to respond to anticoagulant therapy
  • PET-CT may help to differentiate between tumor tissue and thromboembolism

Recommended reading

Hoffmeier et al.
Leiomyosarcoma of the pulmonary artery – a diagnostic chameleon
European Journal of Cardio-thoracic Surgery 20 (2001) 1049–1051

Farsad et al.
Thromboembolism in Pulmonary Artery Sarcoma
Clin Nucl Med 2009;34: 239–240

Chen et al.
Clinicopathological and immunohistochemical features of pulmonary artery sarcoma: A report of three cases and review of the literature
ONCOLOGY LETTERS 11: 2820-2826, 2016

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