Standardization of trans-bronchial lung cryobiopsy in diffuse parenchymal lung diseases is imminent; however, the majority of published series on cryobiopsy include a limited number of patients and are characterized by several differences in procedural technical details. This is an observational, retrospective cohort study. Aim of the study was to suggest some sampling strategies related to transbronchial cryobiopsy in the diagnostic work-up of patients with diffuse parenchymal lung diseases. Six hundred ninety-nine patients with suspected diffuse parenchymal lung disease were recruited. A specific pathological diagnosis was achieved in 614/699 cases (87.8%) and a multidisciplinary diagnosis was obtained in 630/699 cases (90.1%). Diagnostic yield was significantly influenced by the number of samples taken (1 vs ≥ 2 biopsies, p < 0.005). In 60.4% of patients, biopsies were taken from one site and in 39.6% from different sites (in the same lobe or in two different lobes), with a significant increase in diagnostic yield, specifically in patients with fibrotic lung diseases (65.5% vs 93.4%, p < 0.0001). The 2.4 mm or 1.9 mm probes were used, with no differences in terms of diagnostic yield. Regarding safety, pneumothorax occurred in 19.2% and was influenced by baseline lung function; in all patients Fogarty balloon has been used and severe haemorrhage occurred in 0.7% of cases. Three patients (0.4% of cases) died within 30 days after the procedure. We propose some sampling strategies of cryobiopsy which seem to be associated with a higher diagnostic yield and a favorable risk/benefit ratio: sampling at least two samples in different sites, using either the 2.4 mm or the 1.9 mm probe, intubating the patients and using bronchial blockers/catheters.

Background: Transbronchial lung cryobiopsy is an innovative method of obtaining samples from the parenchyma of patients with diffuse parenchymal lung diseases. However, the technique is not yet standardized, and uncertainty exists about the optimal protocol, including the number of samples, the biopsy size, and the choice of the biopsy site. Objectives: To compare the diagnostic yield and complications of cryobiopsy with different strategies adopted to sample lung tissue (number of samples, biopsy site, and sample size). Methods: We prospectively enrolled 46 patients with suspected diffuse parenchymal lung diseases for the diagnosis of which a biopsy was deemed useful. All patients underwent transbronchial lung cryobiopsy, and they were randomly assigned to group A (4 samples obtained from the same segment) or group B (2 samples obtained from one segment and 2 samples obtained from a different segment of the same lobe). Analysis of the samples was performed sequentially (from the first to the last sample), and pathologists reformulated their histopathologic diagnosis with the addition of each sample. Results: The mean diagnostic yield of the procedure combining the 2 groups and performing only the first sampling was 69%. When a second biopsy was performed as well, the mean diagnostic yield improved, but this increase was significant only when the 2 samples were obtained from 2 different segments (96%, group B). Conclusions: This study suggests that the strategy of performing 2 biopsies with a cryoprobe may be associated with an increased diagnostic yield in diffuse parenchymal lung diseases if these samples are obtained from 2 different segments within the same lobe.

Some patients experience pulmonary sequelae after SARS-CoV-2 infection, ranging from self-limited abnormalities to major lung diseases. Morphological analysis of lung tissue may help our understanding of pathogenic mechanisms and help to provide consistent personalised management. The aim of this study was to ascertain morphological and immunomolecular features of lung tissue. Transbronchial lung cryobiopsy was carried out in patients with persistent symptoms and computed tomography suggestive of residual lung disease after recovery from SARS-CoV-2 infection. 164 patients were referred for suspected pulmonary sequelae after COVID-19; 10 patients with >5% parenchymal lung disease underwent lung biopsy. The histological pattern of lung disease was not homogeneous and three different case clusters could be identified, which was mirrored by their clinical and radiological features. Cluster 1 (“chronic fibrosing”) was characterised by post-infection progression of pre-existing interstitial pneumonias. Cluster 2 (“acute/subacute injury”) was characterised by different types and grades of lung injury, ranging from organising pneumonia and fibrosing nonspecific interstitial pneumonia to diffuse alveolar damage. Cluster 3 (“vascular changes”) was characterised by diffuse vascular increase, dilatation and distortion (capillaries and venules) within otherwise normal parenchyma. Clusters 2 and 3 had immunophenotypical changes similar to those observed in early/mild COVID-19 pneumonias (abnormal expression of STAT3 in hyperplastic pneumocytes and PD-L1, IDO and STAT3 in endothelial cells). This is the first study correlating histological/immunohistochemical patterns with clinical and radiological pictures of patients with post-COVID lung disease. Different phenotypes with potentially different underlying pathogenic mechanisms have been identified.

Background: The pathogenetic steps leading to Covid-19 interstitial pneumonia remain to be clarified. Most postmortem studies to date reveal diffuse alveolar damage as the most relevant histologic pattern. Antemortem lung biopsy may however provide more precise data regarding the earlier stages of the disease, providing a basis for novel treatment approaches. Objectives: To ascertain the morphological and immunohistochemical features of lung samples obtained in patients with moderate Covid-19 pneumonia. Methods: Transbronchial lung cryobiopsy was carried out in 12 Covid-19 patients within 20 days of symptom onset. Results: Histopathologic changes included spots of patchy acute lung injury with alveolar type II cell hyperplasia, with no evidence of hyaline membranes. Strong nuclear expression of phosphorylated STAT3 was observed in >50% of AECII. Interalveolar capillaries showed enlarged lumen and were in part arranged in superposed rows. Pulmonary venules were characterized by luminal enlargement, thickened walls, and perivascular CD4⁺ T-cell infiltration. A strong nuclear expression of phosphorylated STAT3, associated with PD-L1 and IDO expression, was observed in endothelial cells of venules and interstitial capillaries. Alveolar spaces macrophages exhibited a peculiar phenotype (CD68, CD11c, CD14, CD205, CD206, CD123/IL3AR, and PD-L1). Conclusions: Morphologically distinct features were identified in early stages of Covid-19 pneumonia, with epithelial and endothelial cell abnormalities different from either classical interstitial lung diseases or diffuse alveolar damage. Alveolar type II cell hyperplasia was a prominent event in the majority of cases. Inflammatory cells expressed peculiar phenotypes. No evidence of hyaline membranes and endothelial changes characterized by IDO expression might in part explain the compliance and the characteristic pulmonary vasoplegia observed in less-advanced Covid-19 pneumonia.

Background: When considering the diagnosis of idiopathic pulmonary fibrosis (IPF), experienced clinicians integrate clinical features that help to differentiate IPF from other fibrosing interstitial lung diseases, thus generating a “pre-test” probability of IPF. The aim of this international working group perspective was to summarize these features using a tabulated approach similar to chest HRCT and histopathologic patterns reported in the international guidelines for the diagnosis of IPF, and to help formally incorporate these clinical likelihoods into diagnostic reasoning to facilitate the diagnosis of IPF. Methods: The committee group identified factors that influence the clinical likelihood of a diagnosis of IPF, which was categorized as a pre-test clinical probability of IPF into “high” (70–100%), “intermediate” (30–70%), or “low” (0–30%). After integration of radiological and histopathological features, the post-test probability of diagnosis was categorized into “definite” (90–100%), “high confidence” (70–89%), “low confidence” (51–69%), or “low” (0–50%) probability of IPF. Findings: A conceptual Bayesian framework was created, integrating the clinical likelihood of IPF (“pre-test probability of IPF”) with the HRCT pattern, the histopathology pattern when available, and/or the pattern of observed disease behavior, into a “post-test probability of IPF.” The diagnostic probability of IPF was expressed using an adapted diagnostic ontology for fibrotic interstitial lung diseases. Interpretation: The present approach will help incorporate the clinical judgment into the diagnosis of IPF, thus facilitating the application of IPF diagnostic guidelines and, ultimately improving diagnostic confidence and reducing the need for invasive diagnostic techniques.

Despite intense investigation, the pathogenesis of COVID-19 and the newly defined long COVID-19 syndrome are not fully understood. Increasing evidence has been provided of metabolic alterations characterizing this group of disorders, with particular relevance of an activated tryptophan/kynurenine pathway as described in this review. Recent histological studies have documented that, in COVID-19 patients, indoleamine 2,3-dioxygenase (IDO) enzymes are differentially expressed in the pulmonary blood vessels, i.e., IDO1 prevails in early/mild pneumonia and in lung tissues from patients suffering from long COVID-19, whereas IDO2 is predominant in severe/fatal cases. We hypothesize that IDO1 is necessary for a correct control of the vascular tone of pulmonary vessels, and its deficiency in COVID-19 might be related to the syndrome’s evolution toward vascular dysfunction. The complexity of this scenario is discussed in light of possible therapeutic manipulations of the tryptophan/kynurenine pathway in COVID-19 and post-acute COVID-19 syndromes.