Nonthrombotic pulmonary embolism (NTPE) is defined as embolisation to the pulmonary circulation of different cell types (adipocytes, haematopoietic, amniotic, trophoblastic or tumour), bacteria, fungi, foreign material or gas. The purpose of this article is to describe the clinical signs, pathogenesis, diagnosis and treatment of the different NTPE subtypes.The complex and diverse pathogenesis of different subtypes of emboli is subject to continuing speculation and is certainly far more complex than ''simple'' mechanical obstruction after embolisation of vascular thrombi. Nonthrombotic emboli may also lead to a severe inflammatory reaction both in the systemic and pulmonary circulation, as well as in the lung.NTPE presents a formidable diagnostic challenge, as the condition often presents with very unusual and peculiar clinical signs that are frequently overlooked. They range from very dramatic acute presentations such as acute respiratory distress syndrome to signs observed late in the disease course. Pathological observations play a key role in the exact diagnosis, and sometimes carefully aspirated blood from the pulmonary artery or specific staining of cells recovered from bronchoalveolar lavage fluid may be helpful. Frequently, lung biopsies revealing severe granulomatous reaction or unfortunate post-mortem pathological investigations of pulmonary tissue are necessary to confirm the diagnosis. Here, we also aim to familiarise the reader with the atypical radiological features of NTPE. Thin-section computed tomography of the lungs showing peculiar radiographic findings, such as a feeding vessel, the so-called tree-in-bud pattern or the appearance of micronodules distributed at the termination of bronchovascular bundles, may be observed in certain forms of NTPE.Increased awareness of NTPE as an underestimated cause of acute and chronic embolism, which may result in acute and chronic pulmonary hypertension, is needed. Despite the fact that detailed descriptions of several forms of NTPE have existed for nearly 100 years, well-designed trials have never been performed to evaluate therapy in the different subsets of these patients.

Subsequent to the widespread use of multidetector computed tomography and growing interest in lung cancer screening, small pulmonary nodules are more frequently detected. The differential diagnosis for a solitary pulmonary nodule is extremely broad and includes both benign and malignant causes. Recognition of early lung cancers is vital, since stage at diagnosis is crucial for prognosis. Estimation of the probability of malignancy is a challenging task, but crucial for follow-up and further work-up. In addition to the clinical setting and metabolic assessment, morphological assessment on thin-section computed tomography is essential. Size and growth are key factors in assessment of the malignant potential of a nodule. The likelihood of malignancy positively correlates with nodule diameter: as the diameter increases, so does the likelihood of malignancy. Although there is a considerable overlap in the features of benign and malignant nodules, the importance of morphology however should not be underestimated. Features that are associated with benignity include a perifissural location and triangular morphology, internal fat and benign calcifications. Malignancy is suspected in nodules presenting with spiculation, lobulation, pleural indentation, vascular convergence sign, associated cystic airspace, bubble-like lucencies, irregular air bronchogram, and subsolid morphology. Nodules often show different features and combination of findings is certainly more powerful.Teaching points• Size of a pulmonary nodule is important, but morphological assessment should not be underestimated.• Lung nodules should be evaluated on thin section CT, in both lung and mediastinal window setting.• Features associated with benignity include a triangular morphology, internal fat and calcifications.• Spiculation, pleural retraction and notch sign are highly suggestive of a malignant nature.• Complex features (e.g. bubble-like lucencies) are highly indicative of a malignant nature.

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This document from the European Society of Thoracic Imaging (ESTI) and the European Society of Radiology (ESR) discusses the role of imaging in the long-term follow-up of COVID-19 patients, to define which patients may benefit from imaging, and what imaging modalities and protocols should be used. Insights into imaging features encountered on computed tomography (CT) scans and potential pitfalls are discussed and possible areas for future review and research are also included. Key Points • Post-COVID-19 pneumonia changes are mainly consistent with prior organizing pneumonia and are likely to disappear within 12 months of recovery from the acute infection in the majority of patients. • At present, with the longest series of follow-up examinations reported not exceeding 12 months, the development of persistent or progressive fibrosis in at least some individuals cannot yet be excluded. • Residual ground glass opacification may be associated with persisting bronchial dilatation and distortion, and might be termed “fibrotic-like changes” probably consistent with prior organizing pneumonia.