Novel method of attaching a suction tube externally to a tracheal tube as an insertion route for a Fogarty catheter in cryobiopsy: Retrospective comparative study.

BACKGROUND: Cryobiopsy use is anticipated to become more common in diagnosing lung diseases. In Japan, inserting a Fogarty catheter through a suction channel above the endotracheal tube's cuff for hemostasis is common practice. However, the rigid nature of the endotracheal tube poses challenges to tracheal intubation using a bronchoscope. The endotracheal tube cuff must be removed to prevent interference during Fogarty catheter insertion. To simplify the procedure and enhance safety, we devised and implemented a method of inserting a hemostatic Fogarty catheter with a suction tube externally attached to a softer endotracheal tube. This study aimed to evaluate the sustainability of this Fogarty catheter insertion method using suction tubes. METHODS: The hemostatic Fogarty catheter insertion method was retrospectively validated. We compared outcomes between 60 patients who underwent the conventional method with a suction channel above the cuff and 50 patients who underwent the novel approach with an externally attached suction tube. RESULTS: The physicians performing bronchoscopy and inserting the Fogarty catheter in the group in which the suction tube was externally attached for Fogarty catheter insertion had little experience. However, the overall bronchoscopy time was shorter; the two groups showed no significant differences in complications. CONCLUSION: Regarding cryobiopsy procedures, using an externally attached suction tube for Fogarty catheter insertion was practical and comparable to the conventional method of using a suction channel above the cuff. This method made the procedure more simple and safe.

Lung Involvement in Adult T-Cell Lymphoma Diagnosed Using Bronchoscopic Cryobiopsy: A Case Report and Review of the Literature.

The diagnosis of pulmonary lymphoma using small tissue samples is difficult and often requires surgical procedures; thus, a less invasive sampling method is desirable. Moreover, pulmonary involvement in adult T-cell lymphoma (ATL) is often difficult to diagnose, especially in cases without characteristic flower cells. Here, we present the case of a 78-year-old man, in whom pathological examination of the transbronchial lung biopsy (TBLB) specimen did not reveal malignant findings; therefore, transbronchial lung cryobiopsy (TBLC) in combination with endobronchial ultrasonography (EBUS) was used to diagnose ATL based on the pathological findings. A literature review identified 18 cases of pulmonary lymphomas diagnosed using TBLC. Among the 19 cases, including our own, 16 cases were of B-cell lymphoma (84.2%), and the present case is the first case of ATL diagnosed using TBLC. Eighty percent of the cases underwent a biopsy (more than two samples) of the middle or lower lobe and were diagnosed without major complications. EBUS was used with TBLC in three cases to identify the location of the pulmonary lesions. In the present case, EBUS was also useful for avoiding vascular biopsy. Although large-scale prospective studies are required to establish precise guidelines for diagnosing pulmonary lymphomas using TBLC, our case report and review contributes to a deeper understanding of the diagnosis of rare diseases.

Pulmonary Langerhans cell histiocytosis diagnosed using transbronchial lung cryobiopsy: A case report.

A 63-year-old Japanese woman with multiple cysts in both lungs on chest computed tomography (CT) was referred to our hospital after a thorough examination, including a transbronchial lung biopsy (TBLB), failed to provide a diagnosis. Based on the findings on chest CT and pathological examination of the bronchoalveolar lavage fluid and transbronchial lung cryobiopsy (TBLC) specimen, the patient was diagnosed with pulmonary Langerhans cell histiocytosis (PLCH). TBLC may replace TBLB as the main diagnostic technique for PLCH, although further studies are required to determine the usefulness of TBLC for the diagnosis of PLCH.

Disseminated Mycobacterium genavense Infection Mimicking Sarcoidosis: A Case Report and Review of Literature on Japanese Patients.

Sarcoidosis is a systemic inflammatory disease characterized by noncaseating epithelioid cell granulomas. However, certain infections can exhibit similar histological findings. We present a case of a 69-year-old man who was initially diagnosed with sarcoidosis and later was confirmed, through 16S rRNA sequencing, to have disseminated Mycobacterium genavense infection. Acid-fast bacteria were detected in the bone marrow biopsy using Ziehl-Neelsen staining, but routine clinical tests did not provide a definitive diagnosis. The patient tested negative for HIV, anti-interferon-gamma antibodies, and genetic immunodeficiency disorders. He was treated with multiple drugs, including aminoglycosides and macrolides, but showed no improvement in fever and pancytopenia. However, these clinical signs responded favorably to steroid therapy. We reviewed 17 Japanese cases of M. genavense infection. All cases were in males; 7/17 (41%) were HIV-negative; and 12/17 (71%) had a decreased CD4 count. Genetic analysis confirmed M. genavense isolation, and macrolides were used universally. Mycobacterium genavense infection is challenging to identify and mimics other systemic inflammatory diseases such as sarcoidosis. There are no standard treatment protocols. Our case report and Japanese case review contribute to understanding this rare disease.

Standardized Classification of Lung Adenocarcinoma Subtypes and Improvement of Grading Assessment Through Deep Learning.

The histopathologic distinction of lung adenocarcinoma (LADC) subtypes is subject to high interobserver variability, which can compromise the optimal assessment of patient prognosis. Therefore, this study developed convolutional neural networks capable of distinguishing LADC subtypes and predicting disease-specific survival, according to the recently established LADC tumor grades. Consensus LADC histopathologic images were obtained from 17 expert pulmonary pathologists and one pathologist in training. Two deep learning models (AI-1 and AI-2) were trained to predict eight different LADC classes. Furthermore, the trained models were tested on an independent cohort of 133 patients. The models achieved high precision, recall, and F1 scores exceeding 0.90 for most of the LADC classes. Clear stratification of the three LADC grades was reached in predicting the disease-specific survival by the two models, with both Kaplan-Meier curves showing significance (P = 0.0017 and 0.0003). Moreover, both trained models showed high stability in the segmentation of each pair of predicted grades with low variation in the hazard ratio across 200 bootstrapped samples. These findings indicate that the trained convolutional neural networks improve the diagnostic accuracy of the pathologist and refine LADC grade assessment. Thus, the trained models are promising tools that may assist in the routine evaluation of LADC subtypes and grades in clinical practice.

Drug-induced interstitial lung disease caused by olaparib: three case reports and review of the Japanese Adverse Drug Event Report database and literature.

BACKGROUND: Olaparib, a poly (ADP-ribose) polymerase (PARP) inhibitor, has demonstrated effectiveness in treating ovarian, breast, and other cancers, particularly those with specific molecular subtypes including, but not limited to, BRCA1/2 mutations. Consequently, its utilization is expected to increase in the future. For this reason, it is important to acknowledge the potential for adverse events associated with olaparib, including the relatively rare but significant risk of drug-induced interstitial lung disease (DIILD). Since DIILD can lead to fatal outcomes, its early detection is crucial. The dissemination of knowledge regarding DIILD can be facilitated through case reports; however, specific reports of DIILD caused by olaparib have only been published in Japanese. To the best of our knowledge, this is the first report in English of our experience with three cases of DIILD caused by olaparib. CASE PRESENTATION: Cases 1, 2, and 3 involved Japanese women with ovarian cancer who had been receiving olaparib at a dose of 600 mg/day. Case 1, a 72-year-old woman who had been on olaparib for 4 months, and case 2, a 51-year-old woman who had been on olaparib for 8 months, reported fever and general malaise. Chest computed tomography (CT) revealed pale ground glass opacity (GGO) similar to hypersensitivity pneumonitis. The severity grade was 2 in both cases. Case 3, a 78-year-old woman who had been on olaparib for 3 weeks, presented with cough and reported dyspnea on exertion. Chest CT revealed non-specific interstitial pneumonia and organizing pneumonia-like shadows. The severity grade was 4. Olaparib was discontinued in all cases. Case 1 received 0.6 mg/kg of prednisolone due to mild hypoxia, while prednisolone was not administered in case 2 due to the absence of hypoxia. Case 3 received steroid pulse therapy due to severe hypoxia. Olaparib administration was not resumed in any patient. CONCLUSION: DIILD caused by olaparib in Japan, including the present three cases, commonly presents with GGO, similar to hypersensitivity pneumonitis on chest CT. The prognosis for the majority of patients is favorable; however, there have been instances of severe cases. Early recognition of drug-induced lung injury and further accumulation of cases is important.

Effect of the 2020 hypersensitivity pneumonitis guideline on the pathologic diagnosis of interstitial pneumonia.

It was reported that the 2020 guideline for hypersensitivity pneumonitis (HP) might result in the overdiagnosis of fibrotic HP (fHP). fHP and other types of interstitial pneumonias have several overlapping characteristics, and a high diagnostic concordance rate of fHP is rarely obtained. Therefore, we investigated the impact of the 2020 HP guideline on the pathological diagnosis of cases previously diagnosed as interstitial pneumonia. We identified 289 fibrotic interstitial pneumonia cases from 2014 to 2019 and classified them into four categories according to the 2020 HP guideline: typical, probable, and indeterminate for fHP and alternative diagnosis. The original pathological diagnosis of 217 cases were compared to their classification as either typical, probable, or indeterminate for fHP according to the 2020 guideline. The clinical data, including serum data and pulmonary function tests, were compared among the groups. Diagnoses changed from non-fHP to fHP for 54 (25%) of the 217 cases, of which, 8 were typical fHP and 46 were probable fHP. The ratio of typical and probable fHP cases to the total number of VATS cases was significantly lower when using transbronchial lung cryobiopsy (p < 0.001). The clinical data of these cases bore a more remarkable resemblance to those diagnosed as indeterminate for fHP than to those diagnosed as typical or probable. The pathological criteria in the new HP guidelines increase the diagnosis of fHP. However, it is unclear whether this increase leads to overdiagnosis, and requires further investigation. Transbronchial lung cryobiopsy may not be helpful when using the new criteria to impart findings for fHP diagnosis.

Pulmonary Langerhans Cell Histiocytosis That Progressed from a Single-system to a Multisystem Form despite Smoking Cessation.

A 36-year-old Japanese man presented with cavities and nodular shadows in the lower lobes of his lungs and osteolytic lesions in the thoracic spine. He was diagnosed with multisystem Langerhans cell histiocytosis (LCH). Three years earlier, he had been noted to have small cavities and granular lesions noted in the upper lobes of his lungs, which later improved with smoking cessation. It was likely that his single-system pulmonary LCH (PLCH) progressed to multisystem LCH despite smoking cessation. Relapse or progression may occur in cases where PLCH lesions improve after smoking cessation. Thus, close follow-up is vital.

Sensitivity of transbronchial lung cryobiopsy in the diagnosis of different interstitial lung diseases.

The accuracy of transbronchial lung cryobiopsy (TBLC) in each disease for pathological and multidisciplinary discussion (MDD) diagnosis is not yet established. METHOD: We investigated 431 patients who were classified by MDD diagnosis and were grouped into the disease categories. For each category or disease, we used TBLC samples to calculate the sensitivities of the pathological diagnosis compared with MDD diagnoses. Further, we compared these sensitivities to pathological diagnoses with all clinical/radiological information. RESULT: The sensitivity for diagnosing idiopathic interstitial pneumonia (IIPs) with TBLC was higher than connective tissue disease associated ILD (CTD-ILD). Idiopathic nonspecific interstitial pneumonia (iNSIP), fibrotic hypersensitivity pneumonitis, and some CTD-ILDs were diagnosed with lower sensitivities compared to IPF. The sensitivity of pathological diagnosis with all clinical/radiological information in IPF was higher than in iNSIP, but not significantly different from other diseases. The overall sensitivity of the pathological diagnosis with clinical/radiological information was 69.0%, significantly higher than without clinical/radiological information. CONCLUSION: The sensitivity of pathological diagnosis with TBLC was low for some diseases except IPF. The addition of all clinical/radiological information increased the sensitivity of pathology diagnosis by TBLC, which was no less sensitive than IPF for all diseases except iNSIP.

Deep-Learning-Aided Detection of Mycobacteria in Pathology Specimens Increases the Sensitivity in Early Diagnosis of Pulmonary Tuberculosis Compared with Bacteriology Tests.

The histopathological diagnosis of mycobacterial infection may be improved by a comprehensive analysis using artificial intelligence. Two autopsy cases of pulmonary tuberculosis, and forty biopsy cases of undetected acid-fast bacilli (AFB) were used to train AI (convolutional neural network), and construct an AI to support AFB detection. Forty-two patients underwent bronchoscopy, and were evaluated using AI-supported pathology to detect AFB. The AI-supported pathology diagnosis was compared with bacteriology diagnosis from bronchial lavage fluid and the final definitive diagnosis of mycobacteriosis. Among the 16 patients with mycobacteriosis, bacteriology was positive in 9 patients (56%). Two patients (13%) were positive for AFB without AI assistance, whereas AI-supported pathology identified eleven positive patients (69%). When limited to tuberculosis, AI-supported pathology had significantly higher sensitivity compared with bacteriology (86% vs. 29%, p = 0.046). Seven patients diagnosed with mycobacteriosis had no consolidation or cavitary shadows in computed tomography; the sensitivity of bacteriology and AI-supported pathology was 29% and 86%, respectively (p = 0.046). The specificity of AI-supported pathology was 100% in this study. AI-supported pathology may be more sensitive than bacteriological tests for detecting AFB in samples collected via bronchoscopy.

MIXTURE of human expertise and deep learning-developing an explainable model for predicting pathological diagnosis and survival in patients with interstitial lung disease.

Interstitial pneumonia is a heterogeneous disease with a progressive course and poor prognosis, at times even worse than those in the main cancer types. Histopathological examination is crucial for its diagnosis and estimation of prognosis. However, the evaluation strongly depends on the experience of pathologists, and the reproducibility of diagnosis is low. Herein, we propose MIXTURE (huMan-In-the-loop eXplainable artificial intelligence Through the Use of REcurrent training), an original method to develop deep learning models for extracting pathologically significant findings based on an expert pathologist's perspective with a small annotation effort. The procedure of MIXTURE consists of three steps as follows. First, we created feature extractors for tiles from whole slide images using self-supervised learning. The similar looking tiles were clustered based on the output features and then pathologists integrated the pathologically synonymous clusters. Using the integrated clusters as labeled data, deep learning models to classify the tiles into pathological findings were created by transfer-learning the feature extractors. We developed three models for different magnifications. Using these extracted findings, our model was able to predict the diagnosis of usual interstitial pneumonia, a finding suggestive of progressive disease, with high accuracy (AUC 0.90 in validation set and AUC 0.86 in test set). This high accuracy could not be achieved without the integration of findings by pathologists. The patients predicted as UIP had poorer prognosis (5-year overall survival [OS]: 55.4%) than those predicted as non-UIP (OS: 95.2%). The Cox proportional hazards model for each microscopic finding and prognosis pointed out dense fibrosis, fibroblastic foci, elastosis, and lymphocyte aggregation as independent risk factors. We suggest that MIXTURE may serve as a model approach to different diseases evaluated by medical imaging, including pathology and radiology, and be the prototype for explainable artificial intelligence that can collaborate with humans.

Proportion of biopsy specimens containing a tumor when compared to all biopsy specimens by transbronchial biopsy.

Background: The lung cancer biopsy specimens obtained by endobronchial ultrasound-guide sheath (EBUS-GS) trans lung biopsy occasionally do not contain cancer cells. It is a problem that there is a possibility that they may not contain cancer cells. Aim of the study: To investigate the proportion of biopsy specimens containing cancer cells in total biopsy specimens. Materials & methods: Patients with lung cancer diagnosed by EBUS-GS were selected. The primary end point was the proportion of specimens containing tumors in the total specimens obtained by EBUS-GS. Results: Twenty-six patients were investigated. The percentage of specimens containing cancer cells in the total specimens was 79.0%. Conclusion: The proportion of biopsy specimens containing cancer cell to all biopsy specimens by EBUS-GS was high, but not 100%.

The lung cancer biopsy specimens obtained by trans lung biopsy occasionally do not contain cancer cells. It is a problem that there is a possibility that they may not contain cancer cells. If the biopsy specimens contained no malignant cells, there was a possibility that accurate genetic test would not be performed and as a result, the correct molecular targeted drug would not be used. It is important to investigate the proportion of biopsy specimens containing cancer cells in total biopsy specimens. In this study, we showed the percentage of specimens containing cancer cells in the total specimens was 79.0%. This result should be considered to perform genetic test from biopsy specimens.

Combined detection of lymphocyte clonality and MALT1 translocations in bronchoalveolar lavage fluid for diagnosing pulmonary lymphomas.

Diagnosis of pulmonary lymphoma using small tissue samples is difficult and often requires surgical procedures; thus, a less invasive sampling method is desirable. We previously showed that pulmonary mucosa-associated lymphoid tissue (MALT) lymphoma can be diagnosed by detecting MALT lymphoma translocation gene 1 (MALT1) translocations in bronchoalveolar lavage fluid (BALF) cells. Analysis of B-cell clonality based on immunoglobulin heavy chain (IGH) gene rearrangements was also reportedly useful for diagnosing pulmonary lymphoma. The aim of this prospective multicenter study was to evaluate the yet unknown diagnostic potential of combined detection of MALT1 translocations and clonality using BALF. We analyzed B- and T-cell clonality based on IGH and T-cell receptor (TCR) rearrangements together with MALT1 translocations using BALF of patients with clinically suspected pulmonary lymphomas. In total, 39 patients were evaluated and categorized into three groups: B-cell lymphoma, lymphoproliferative disorders, and other diseases. IGH rearrangement detection for B-cell lymphoma diagnosis exhibited sensitivity and specificity of 88.9% and 90.0%, respectively. TCR rearrangements were not observed in patients with B-cell lymphomas. The presence of IGH rearrangements together with the absence of TCR rearrangements indicated 96.0% specificity for the diagnosis of B-cell lymphoma. The sensitivity and specificity of MALT1 translocations for diagnosing MALT lymphoma were 28.6% and 100%, respectively. The combined detection of lymphocyte clonality and MALT1 translocations using BALF is suitable for screening and diagnosis of B-cell lymphomas. Analysis of specific genes such as MALT1 should improve the precision of B-cell lymphoma diagnosis.

Determining Response to Treatment for Drug-Induced Bronchocentric Granulomatosis by the Forced Oscillation Technique.

Anti-tumor necrosis factor alpha (TNFα) therapy is widely used to treat various inflammatory conditions. Paradoxically, there are several case reports describing the development of bronchocentric granulomatosis treated with TNFα inhibitors, and it is difficult to determine the effect of treatment using conventional spirometry because the lesions are located in small airways. However, it has been reported that the forced oscillation technique (FOT) is useful in the evaluation of small airway disease in bronchial asthma or chronic obstructive pulmonary disease. We performed the FOT to determine the effect of treatment on bronchocentric granulomatosis and found it to be useful. We report the case of a 55-year-old female with ulcerative colitis who was treated with golimumab and who developed bronchocentric granulomatosis as a sarcoid-like reaction to golimumab. She was successfully treated with prednisone, and the treatment efficacy was confirmed by the FOT. The FOT may be useful in the evaluation of small airway disease in bronchocentric granulomatosis. This case may help inform clinicians of the usefulness of the FOT to assess small airway disease in various diseases.

Idiopathic desquamative interstitial pneumonia diagnosed using transbronchial lung cryobiopsy: A case report.

A 60-year-old Japanese man with a history of heavy smoking came to our hospital for a detailed examination, suspecting interstitial pneumonia because of gradually increasing dyspnea on exertion over a period of one year. Chest high-resolution computed tomography revealed ground-glass shadows with emphysematous changes. Pathological analysis of samples obtained using transbronchial lung cryobiopsy revealed an accumulation of alveolar macrophages with abundant eosinophilic cytoplasm in the alveolar space. Following a multidisciplinary discussion, the patient was diagnosed with desquamative interstitial pneumonia. To our knowledge, this is the first detailed report of desquamative interstitial pneumonia diagnosed using transbronchial lung cryobiopsy.

Recognition of Connective Tissue Disease-Related Interstitial Pneumonia Based on Histological Score-A Validation Study of an Online Diagnostic Decision Support Tool.

OBJECTIVES: to evaluate the number of cases of idiopathic pulmonary fibrosis (IPF) that included histological features of connective tissue disease (CTD) and to check whether they demonstrated the clinical features of CTD, using a previously reported CTD-interstitial pneumonia (IP) index that histologically differentiates CTD-associated and idiopathic IP. METHODS: patients diagnosed with IPF following video-assisted thoracoscopic biopsy through multidisciplinary team diagnosis between 2014 and 2017 were selected. Pathological observation was made by four pathologists who scored eight observational items needed for the CTD-IP index. Cases determined as CTD, by the CTD-IP index, were extracted, and their clinical features were compared. RESULTS: a total of 94 cases of IPF were identified, of which 20 were classified into the CTD group using the CTD-IP index with reasonable interobserver agreement (k = 0.76). Cases pathologically classified into the CTD group were significantly associated with female sex, non-smoking history, autoantibody positivity, and CTD symptoms (p = 0.01, 0.03, 0.01, and 0.04, respectively). CONCLUSIONS: patients with IPF with pathological findings of CTD showed clinical characteristics similar to those of patients with CTD.

Remarkable response to pembrolizumab with platinum-doublet in PD-L1-low pulmonary sarcomatoid carcinoma: A case report.

Pulmonary sarcomatoid carcinoma (SC) is an aggressive subtype of lung cancer that exhibits resistance to cytotoxic chemotherapy. Although programmed cell death 1 (PD-1) inhibitors have been reported to show antitumor effects in patients with high programmed death-ligand 1 (PD-L1) expressing SC, the efficacy of combined therapy with PD-1 inhibitor plus cytotoxic chemotherapy has not previously been clarified. We herein report a case of SC with low expression of PD-L1 and few pre-existing tumor-infiltrating lymphocytes which showed a remarkable response to pembrolizumab plus cytotoxic chemotherapy as first-line treatment. Our findings suggest that combined treatment might enhance the immunogenic response, even in immunologically ignored SCs.

Pneumoconiosis with a Sarcoid-Like Reaction Other than Beryllium Exposure: A Case Report and Literature Review.

Background: Chronic beryllium disease (CBD) is a granulomatous disease that resembles sarcoidosis but is caused by beryllium. Clinical manifestations similar to those observed in CBD have occasionally been reported in exposure to dusts of other metals. However, reports describing the clinical, radiographic, and pathological findings in conditions other than beryllium-induced granulomatous lung diseases, and detailed information on mineralogical analyses of metal dusts, are limited. Case presentation: A 51-year-old Japanese man with rapidly progressing nodular shadows on chest radiography, and a 10-year occupation history of underground construction without beryllium exposure, was referred to our hospital. High-resolution computed tomography showed well-defined multiple centrilobular and perilobular nodules, and thickening of the intralobular septa in the middle and lower zones of both lungs. No extrathoracic manifestations were observed. Pathologically, the lung specimens showed 5-12 mm nodules with dust deposition and several non-necrotizing granulomas along the lymphatic routes. X-ray analytical electron microscopy of the same specimens revealed aluminum, iron, titanium, and silica deposition in the lung tissues. The patient stopped smoking and changed his occupation to avoid further dust exposure; the chest radiography shadows decreased 5 years later. Conclusion: The radiological appearances of CBD and sarcoidosis are similar, although mediastinal or hilar lymphadenopathy is less common in CBD and is usually seen in the presence of parenchymal opacities. Extrathoracic manifestations are also rare. Despite limited evidence, these findings are similar to those observed in pneumoconiosis with a sarcoid-like reaction due to exposure to dust other than of beryllium. Aluminum is frequently detected in patients with pneumoconiosis with a sarcoid-like reaction and is listed as an inorganic agent in the etiology of sarcoidosis. It was also detected in our patient and may have contributed to the etiology. Additionally, our case suggests that cessation of dust exposure may contribute to improvement under the aforementioned conditions.

Proposed method of histological separation between connective tissue disease-associated interstitial pneumonia and idiopathic interstitial pneumonias.

OBJECTIVES: Idiopathic interstitial pneumonia (IIP) and connective tissue disease -associated interstitial pneumonia (CTD-IP) are the two most common types of interstitial pneumonia. IIP and CTD-IP share common histological features, yet their clinical management is different. Separation of the two conditions based solely on histology can be challenging, and there are no established criteria. MATERIALS AND METHODS: We selected 105 consecutive cases of IIP (79 usual interstitial pneumonia and 26 non-specific interstitial pneumonia) and 49 cases of CTD-IP for derivation and 32 cases of IIP and 10 cases of CTD-IP for validation. Fourteen histological parameters were evaluated independently by two pathologists for derivation group and graded into 0 to 3. The association between the score for each marker and a diagnosis of CTD was investigated using Fisher's exact test and stepwise logistic regression analysis. A formula for calculating the probability of IIP and CTD-IP was constructed by the markers identified in the regression test with coefficients for each finding. The formula was confirmed using validation case group. RESULTS: Stepwise logistic regression analysis showed that plasmacytosis, lymphoid follicle with germinal center, and airspace fibrin were suggestive of CTD-IP and that fibroblastic foci, smooth muscle hyperplasia, cellular IP, dense perivascular collagen, and fat metaplasia were suggestive of IIP. The formula used to calculate the probabilities based on estimated values for each finding was created, and user-friendly web based app was composed at www.ctdip.com. On the validation study, 30 out of 32 IIP and eight out of 10 CTD-IPs were distinguished correctly by the app (Specificity: 93%, Sensitivity: 80%). CONCLUSIONS: We identified histological markers and derived a practical formula and user-friendly app to distinguish CTD-IPs from IIP.