Pulmonary artery intimal sarcomas are rare and very aggressive tumors, with variable presentation, and are often misdiagnosed as acute pulmonary embolisms or chronic thromboembolic pulmonary hypertension. We report a case of a 44-year-old man who presented after accidental smoke inhalation and was eventually diagnosed with PAIS, despite reporting no specific symptoms at the time of diagnosis.
A 44-year-old man with a history of cigarette smoking presented to our hospital with dyspnea following smoke inhalation during an accidental fire at his residence. Upon admission, he was clinically stable with an unremarkable physical examination, without hypoxia or elevated carboxyhemoglobin levels on arterial blood gas test. Imaging evaluation with chest radiography revealed a large dense opacity in the left upper lobe (LUL). A subsequent high-resolution chest computed tomography (CT) scan demonstrated a 2.6 × 2.5 cm cavitary lesion in the same location. The patient was discharged with a 4-week course of oral amoxicillin–clavulanate for a presumptive diagnosis of lung abscess.
After completion of antibiotic therapy, a repeat chest CT scan revealed multiple small cavitary lesions throughout the left lung ( Figure 1 A, white star). Given the uncertain nature of these findings, an 18F-fluorodeoxyglucose positron emission tomography–computed tomography (18F-FDG PET-CT) scan was performed. This demonstrated multiple consolidations and cavitary lesions in the left lung with variable FDG uptake, as well as a filling defect in the main pulmonary artery ( Figure 1 A, red arrow), which also exhibited increased FDG uptake ( Figure 1 B, black arrow). The patient was subsequently admitted to our ward and treated with low molecular-weight heparin for a presumptive diagnosis of pulmonary embolism. To evaluate alternative diagnoses, including right-sided infective endocarditis, multiple blood cultures were obtained that were all negative. A transesophageal echocardiogram revealed a 1.2 × 1.1 cm cystic mass on the pulmonary valve with a large mobile extension into the main pulmonary artery ( Figure 1 C, white arrow). Further work-up, including serology for antinuclear antibodies (ANA), antineutrophil cytoplasmic antibodies (ANCA), and common antibodies associated with antiphospholipid antibody syndrome (APLS) were all negative.
Panel A: Transverse plane PET-CT scan of the chest, showing a LLL lesion (white star) and a central filling defect involving the main pulmonary artery (red arrow). Panel B: Transverse plane PET-CT scan of the chest, demonstrating increased FDG uptake in the pulmonary artery filling defect (black arrow). Panel C: Transesophageal echocardiography, mid-esophageal view indicating a large cystic mass involving the pulmonary valve and extending into the main pulmonary artery (white arrow).
Bronchoscopy with bronchoalveolar lavage (BAL) and endobronchial ultrasound guided biopsies of lesions in the LUL and left lower lobe (LLL) were performed. BAL cultures, including mycobacterial cultures, were negative, as were galactomannan and broad-range fungal polymerase chain reaction (PCR) tests. Histopathological examination of the lung lesions and a lymph node sampled via transbronchial biopsy revealed necrotic tissue with negative stains for Keratin 7, Keratin 20, P40, INSM1, and TTF1, thus proving insufficient for diagnosis.
Question 1: Which of the following diagnoses is more likely at this point?
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1.
Pulmonary embolism.
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2.
Infective endocarditis of the pulmonary valve.
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3.
Primary tumor of the pulmonary vasculature.
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4.
Libman-Sacks endocarditis.
Question 1 Answer: C
Pulmonary embolisms arising from ‘bland’ venous thromboembolism do not usually exhibit increased FDG uptake during PET-CT scans. Infective endocarditis of the pulmonic valve usually occurs in intravenous drug users and is more commonly associated with Staphylococcus aureus bacteremia and a septic clinical presentation. Libman-Sacks endocarditis can occur in patients with systemic lupus erythematosus, the antiphospholipid syndrome, and certain malignancies, and may rarely involve the pulmonary valve, however in this case, the serologies associated with these diagnoses were all negative, and biopsy of a lesion assumed to be pulmonary dissemination from the primary lesion did not exhibit typical features of Libman-Sacks endocarditis. The correct answer is C, a primary tumor of the pulmonary vasculature.
A transthoracic core needle (Tru-Cut) biopsy of an FDG-avid LLL lesion was therefore performed. Histopathological evaluation demonstrated atypical mesenchymal cells suspicious for sarcoma. Immunohistochemical staining was positive for smooth muscle actin ( Figure 2 D) and FLI1 ( Figure 2 E), and negative for pan-cytokeratin, CD34, CD31, desmin, and S100. The Ki-67 proliferation index was approximately 20%. MDM2 a.m. plification was detected. ERG and CAMTA1 staining were negative. Based on these findings, a diagnosis of primary pulmonary artery intimal sarcoma (PAIS) with metastatic dissemination to the left lung was established. The patient was started on combination chemotherapy with ifosfamide and doxorubicin and is currently in stable clinical condition.
