EBUS-guided cryobiopsy in the diagnosis of thoracic disorders.

BACKGROUND: Endobronchial Ultrasound (EBUS) has emerged as a crucial tool for diagnosing intrathoracic disorders, particularly in the staging of lung cancer. However, its diagnostic capabilities in the context of benign and rare diseases remain a subject of debate. AIM: to investigate the diagnostic yield and safety of EBUS-transbronchial mediastinal cryobiopsy (EBUS-TMC) in comparison to EBUS-transbronchial needle aspiration (TBNA) for a broad spectrum of intrathoracic diseases. METHODS: a single-centre retrospective observational study conducted on 48 patients who underwent both EBUS-TBNA and endobronchial ultrasound-transbronchial mediastinal cryobiopsy (EBUS-TMC) in the same procedure between August 2021 and October 2023. RESULTS: The overall diagnostic yield of EBUS-TMC surpassed that of EBUS-TBNA (95.8% vs 54.1 %), notably excelling in the diagnosis of sarcoidosis (92.8% vs 78.5 %), rare mediastinal disorders (100% vs 0 %), hyperplastic lymphadenopathy (100% vs 0 %), and lymphoproliferative disease (100% vs 0 %). No significant differences were observed in the diagnosis of NSCLC and SCLC. Samples obtained through EBUS-TMC facilitated the acquisition of NGS and immunohistochemical analyses more readily. CONCLUSION: EBUS-TMC may contribute to the precise diagnosis and subtyping of mediastinal diseases, especially lymphomas and rare mediastinal tumors, thereby reducing the number of non-diagnostic procedures.

A rare case of thoracic brucellosis misdiagnosed as malignant tumor and literature review.

Brucellosis remains a major public health problem worldwide. It is commonly found in most developed and developing countries, such as the Mediterranean region, the Middle East, and Latin America. In China, brucellosis is mainly distributed in some of the northern provinces and is relatively rare in Shandong province. Brucellosis has a variety of clinical manifestations, with fever, sweating, fatigue, and migratory joint pain being the most common. Because of the non-specific clinical symptoms, brucellosis is often misdiagnosed as other diseases. Here, we report a rare case of brucellosis of thoracic vertebrae misdiagnosed as thoracic malignant tumor and present a review of related literature.

Fetal body MRI and its application to fetal and neonatal treatment: an illustrative review.

This Review depicts the evolving role of MRI in the diagnosis and prognostication of anomalies of the fetal body, here including head and neck, thorax, abdomen and spine. A review of the current literature on the latest developments in antenatal imaging for diagnosis and prognostication of congenital anomalies is coupled with illustrative cases in true radiological planes with viewable three-dimensional video models that show the potential of post-acquisition reconstruction protocols. We discuss the benefits and limitations of fetal MRI, from anomaly detection, to classification and prognostication, and defines the role of imaging in the decision to proceed to fetal intervention, across the breadth of included conditions. We also consider the current capabilities of ultrasound and explore how MRI and ultrasound can complement each other in the future of fetal imaging.

Ultrasound-guided percutaneous biopsy of thoracic lesions: high diagnostic yield and low complication rate.

AIM: To investigate the use of ultrasound (US)-guided biopsy of thoracic lesions aiming to determine diagnostic success and complication rates and to identify factors that may affect sample adequacy and safety. MATERIAL AND METHODS: This was a retrospective study of consecutive percutaneous US-guided biopsy over 10-year period, including 147 procedures in 146 patients (66 ± 7 years, 83 men, 63 women) with lesions located in the lung (67/147), chest wall (54/147), mediastinum (14/147) and pleura (12/147). Overall diagnostic success, yield for benign and malignant diagnoses and diagnostic success according to lesion location, biopsy type (fine-need aspiration [FNA] or core-needle biopsy [CNB]) and number of specimens were calculated. Presence of complications and effect of age, lesion location, biopsy type, and number of specimens were measured. RESULTS: The overall diagnostic success rate was 90.5% and was similar for malignant (90.6%) and benign (87.5%) diagnoses. Specimen adequacy was similar for FNA and CNB (91.2% and 88.9%, p=0.66); number of specimens did not affect yield. Diagnostic success was highest for mediastinal and chest wall lesions (92.9% and 94.4%) and lowest for pleural lesions (75%), albeit not statistically significant (p=0.45). Complications occurred in 4/147(2.7%) cases, exclusively in lung lesions, and were not associated with any covariates analysed. CONCLUSIONS: US-guided biopsy is an effective and safe technique for diagnosis of thoracic lesions, with high diagnostic yield and low complication rate. In the presence of an adequate acoustic window, US guidance can be valuable for diagnosis of peripheral lung and mediastinal lesions. Radiologists performing thoracic biopsy should be encouraged to implement or expand the use of US guidance in their practice.

Complete resections of giant thorax masses and experienced difficulties.

INTRODUCTION: Thoracic giant masses do not have a clear definition. In some publications, giant thoracic mass definition is used in tumors whose long axis is> 10 cm and in other publications covering more than 50% of the hemithorax. In this study, demographic data of patients with a massive resectable giant thoracic mass and the difficulties and experiences experienced in the peroperative process were reviewed with a general perspective. MATERIALS AND METHODS: 14 giant intrathoracic masses operated at the department of Thoracic Surgery, School of Medicine, Ankara University were included in the study. The masses occupying more than half of the hemithorax and mediastinal lesions with a long axis of 15 cm or larger radiologically were included and evaluated. RESULT: 9 (64.3%) of our patients were male and 9 (35.7%) were female. The average age was 49.2 ± 17.1(between18-68). The tumor localizations of our patients were determined as 9 (64.2%) hemithorax and 5 (35.8%) mediastinal. When the radiological and intraoperative dimensions were examined separately, it was observed that the mean of long axis of CT image is average 18 ± 3.8 cm (between 12 cm and 26 cm), and the mean of long axis of specimen is average 18.14 ± 3.6 cm (between 15 cm and 23 cm). The heaviest mass was average 844 ± 473 g (350 g-2204 g). CONCLUSIONS: The surgical maneuvers and hence the excision of giant masses become difficult to operate due to the narrow localization of the masses and the frequent invasions of adjacent vascular structures and nerve tissues. However, complete resection of these slowly growing and generally encapsulated masses can provide the cure.

Thoracic splenosis: Case report of a symptomatic case.

Thoracic splenosis is the autotransplantation of splenic tissue in the left thoracic cavity as a result of a splenic injury. This rare pathology is usually asymptomatic and may be discovered on incidental imaging, but the diagnosis often requires invasive procedures such as surgery in order to eliminate a neoplasic origin. We report a rare symptomatic case of a 39-year-old man presenting with chest pain and multiple nodules revealed on a computed tomography scan. The patient underwent a surgical exploration and the pathological studies concluded to a thoracic splenosis. Indeed, the previous medical history of the patient revealed a left thoraco-abdominal traumatism during childhood. The aim of this paper is to emphasize that the diagnosis can now be performed using only imaging techniques such as technetium-99 sulfur colloid or labelled heat-denatured red blood cell scintigraphy to avoid unnecessary invasive procedures including thoracotomy.

Chondromesenchymal hamartomas in a 24-year-old male mimicking a posterior mediastinal tumor and a 5-month-old boy with postoperative disseminated intravascular coagulation: two case reports.

BACKGROUND: Chondromesenchymal hamartoma of the chest wall is a rare, benign disease that usually presents at birth or in early infancy. It typically involves one or more ribs, forming a unilateral or bilateral extrapleural mass. Patients may be asymptomatic or complain of mild respiratory distress depending on tumor size and location. To the best of our knowledge, only two of the approximately 100 cases reported so far are adults. CASE PRESENTATION: We present two cases of chondromesenchymal hamartoma. The first case involved the left fifth rib in a 24-year-old male, in close proximity to the fifth vertebral body in the left posterior mediastinum, mimicking a posterior mediastinal tumor on imaging. The tumor was excised via thoracoscopy and the patient had an uneventful postoperative course. The second case was that of a 5-month-old boy, who had a tumor involving the left fifth and sixth ribs which caused thoracic cage collapse. Following en bloc resection of the tumor and the involved rib segments, the patient was transferred to the intensive care unit for treatment of pulmonary infection and disseminated intravascular coagulation (DIC). He was discharged from the hospital in stable condition 11 days later. On histopathology, the tumor was found to be a chondromesenchymal hamartoma with immature spindle-shaped mesenchymal cells, plate-like hyaline cartilage, areas of woven bone formation, endochondral ossification and calcification, osteoclastic giant cells, and secondary aneurysmal bone cysts. CONCLUSIONS: Although the presently reported cases have morphological characteristics similar to previously reported ones, they had distinct radiological and clinical characteristics. Patient 1 is only the third report of an adult with chondromesenchymal hamartoma. His case was characterized by its radiological appearance mimicking a posterior mediastinal tumor. Patient 2 represents the first documentation of DIC as a postoperative complication following excision of a chondromesenchymal hamartoma. We present these two cases to provide clinicopathological insights regarding this extremely rare tumor that are relevant to both pathologists and clinicians.

Establishment and Characterization of a Stromal Cell Line Derived From a Patient With Thoracic Endometriosis.

Thoracic endometriosis (TE) syndrome is a clinical condition known as an extrapelvic form of endometriosis with the presence of functioning endometrial tissue involving lung parenchyma, pleura, chest wall, or diaphragm. In an effort to obtain an endometriosis ex vivo model, we established the spontaneously growing TH-EM1 cell line from endometriotic implants in lung parenchyma from a woman with TE. Maintained in long-term culture, the cells grew as large mesenchymal-like cells with a doubling time between 5 and 6 days. Treatment with medroxyprogesterone acetate (10-7 mol/L) inhibited the TH-EM1 cells growth and induced morphological changes to an epithelial-like cells. Strong expression of the nuclear estrogen receptors, progesterone receptors, and erytropoietin receptors were found in both the pulmonary implant and the TH-EM1 cells by immunohistochemical analysis. Consistent immunoreactivity of TH-EM1 cells for CD9, CD13, CD73, CD90, CD105, and CD157 was revealed by flow cytometry. Likewise, the embryonic markers, SRY-box 2 (SOX-2) and the Nanog molecules, were detected in 76% and 52% of the cells, while fetal hemoglobin and a-globin were detected in 76% and 65% of TH-EM1 cells, respectively. By RHG banding, normal metaphases were observed, while the microarray chromosomal analysis showed gains of DNA sequences located on the segments 8p23.1, 11p15.5, and 12p11.23. The described in vitro cellular model can serve as a useful tool to study the pathogenesis of endometriosis and to improve the knowledge of molecular mechanisms controlling the endometriotic cell dissemination potential.

Diagnostic yield of rapid on-site evaluation transbronchial needle aspiration versus conventional transbronchial needle aspiration: a single center experience.

Trans-bronchial needle aspiration allows lymph node sampling in several thoracic conditions; the ability of Rapid On-Site Evaluation (ROSE) to predict the final diagnosis in this setting has not been well characterized. We performed a retrospective study to establish the utility of ROSE in the diagnosis of thoracic diseases with mediastinal lymph node involvement. We retrospectively reviewed 297 patients with hilar-mediastinal lymph node enlargement detected at CT scan from January 2013 to April 2016. 201 patients underwent conventional TBNA; in 96 patients, TBNA procedure was performed by on-site presence of a team of pathologists and research morphologists. Lung neoplasms, sarcoidosis, infections and lymphoma were the most common diseases diagnosed with TBNA samples. TBNA simultaneously performed in combination with ROSE produced an increase in percentage of appropriate samples compared to single cTBNA (adequate samples cTBNA vs ROSE-TBNA: 73% vs 81%; p<0.05). Our observations indicate an increase in adequacy of fine needle aspirations and increased diagnostic yield in the ROSE group. In conclusions, ROSE may serve to reduce procedure time and enhance sample triaging therefore limiting the need for further invasive diagnostic testing.

[Pyogenic granuloma with satellitosis]. / Satellitenrezidiv bei Granuloma pyogenicum.

A 16-year-old female developed a satellite-like recurrence of a pyogenic granuloma on her thorax 2 weeks after complete excision. Treatment with a pulsed dye laser led to a complete resolution. BRAF and RAS mutations detected in the pyogenic granuloma are considered major driver mutations. Whether these findings are also of importance for the etiopathogenesis of satellitosis is unknown. In our patient, no BRAF or NRAS mutation could be detected.

Extrapelvic Endometriosis: A Systematic Review.

OBJECTIVE: To conduct a systematic review of the literature on patients with extrapelvic deep endometriosis. DATA SOURCES: A thorough search of the PubMed/Medline, Embase, and Cochrane databases was performed. METHODS OF STUDY SELECTION: Studies in the last 20 years that reported on primary extrapelvic endometriosis were included (PROSPERO registration number CRD42019125370). TABULATION, INTEGRATION, AND RESULTS: The initial search identified 5465 articles, and 179 articles, mostly case reports and series, were included. A total of 230 parietal (PE), 43 visceral (VE), 628 thoracic (TE), 6 central nerve system, 12 extrapelvic muscle or nerve, and 1 nasal endometriosis articles were identified. Abdominal endometriosis was divided into PE and VE. PE lesions involved primary lesions of the abdominal wall, groin, and perineum. When present, symptoms included a palpable mass (99%), cyclic pain (71%) and cyclic bleeding (48%). Preoperative clinical suspicion was low, the use of tissue diagnosis was indeterminate (25%), and a few (8%) malignancies were suspected. Surgical treatment for PE included wide local excision (97%), with 5% recurrence and no complications. Patients with VE involving abdominal organs - kidneys, liver, pancreas, and biliary tract - were treated surgically (86%) with both conservative (51%) and radical resection (49%), with 15% recurrence and 2 major complications reported. In patients with TE involving the diaphragm, pleura, and lung, isolated and concomitant lesions occurred and favored the right side (80%). Patients with TE presented with the triad of catamenial pain, pneumothorax, and hemoptysis. Thoracoscopy with resection followed by pleurodesis was the most common procedure performed, with 29% recurrence. Adjuvant medical therapy with gonadotropin-releasing hormone was administered in 15% of cases. Preoperative magnetic resonance imaging was performed in all cases of nonthoracic and nonabdominal endometriosis. Common symptoms were paresthesia and cyclic pain with radiation. Surgical resection was reported in 84%, with improvement of symptoms. CONCLUSION: Extrapelvic endometriosis, traditionally thought to be rare, has been reported in a considerable number of cases. Heightened awareness and clinical suspicion of the disease and a multidisciplinary approach are recommended to achieve a prompt diagnosis and optimize patient outcomes. Currently, there are no comparative studies to provide recommendations regarding optimal diagnostic methods, treatment options, and outcomes for endometriosis involving extrapelvic sites.

Thoracic calcifications on magnetic resonance imaging: correlations with computed tomography.

OBJECTIVE: To identify the characteristics of thoracic calcifications on magnetic resonance (MR) imaging, as well as correlations between MR imaging and CT findings. METHODS: This was a retrospective study including data on 62 patients undergoing CT scans and MR imaging of the chest at any of seven hospitals in the Brazilian states of Rio Grande do Sul, São Paulo, and Rio de Janeiro between March of 2014 and June of 2016 and presenting with calcifications on CT scans. T1- and T2-weighted MR images (T1- and T2-WIs) were semiquantitatively analyzed, and the lesion-to-muscle signal intensity ratio (LMSIR) was estimated. Differences between neoplastic and non-neoplastic lesions were analyzed. RESULTS: Eighty-four calcified lesions were analyzed. Mean lesion density on CT was 367 ± 435 HU. Median LMSIRs on T1- and T2-WIs were 0.4 (interquartile range [IQR], 0.1-0.7) and 0.2 (IQR, 0.0-0.7), respectively. Most of the lesions were hypointense on T1- and T2-WIs (n = 52 [61.9%] and n = 39 [46.4%], respectively). In addition, 19 (22.6%) were undetectable on T1-WIs (LMSIR = 0) and 36 (42.9%) were undetectable on T2-WIs (LMSIR = 0). Finally, 15.5% were hyperintense on T1-WIs and 9.5% were hyperintense on T2-WIs. Median LMSIR was significantly higher for neoplastic lesions than for non-neoplastic lesions. There was a very weak and statistically insignificant negative correlation between lesion density on CT and the following variables: signal intensity on T1-WIs, LMSIR on T1-WIs, and signal intensity on T2-WIs (r = -0.13, p = 0.24; r = -0.18, p = 0.10; and r = -0.16, p = 0.16, respectively). Lesion density on CT was weakly but significantly correlated with LMSIR on T2-WIs (r = -0.29, p < 0.05). CONCLUSIONS: Thoracic calcifications have variable signal intensity on T1- and T2-weighted MR images, sometimes appearing hyperintense. Lesion density on CT appears to correlate negatively with lesion signal intensity on MR images.

A Case of Mesenchymal Hamartoma of the Chest Wall in a 4-Month-Old Infant.

BACKGROUND Mesenchymal hamartoma of the chest wall is a rare benign lesion that typically presents in early infancy. However, the clinical presentation can be atypical, with imaging features that mimic infection or malignancy. Imaging combined with histopathology is essential in the diagnosis. A case of mesenchymal hamartoma of the chest wall in a 4-month-old infant is presented. CASE REPORT A 4-month-old infant had an incidental finding of a large right-sided chest wall mass. Initial imaging included thoracoabdominal ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI). Histology of an initial open biopsy was inconclusive. The diagnosis of mesenchymal hamartoma was confirmed by histology of the resection specimen, which showed a benign, mixed, chondroid, mesenchymal, and cystic hamartoma with areas of calcification and ossification. CONCLUSIONS This case showed that the diagnosis of mesenchymal hamartoma of the chest wall, which is characterized by heterogeneous components, may require a combined approach for the diagnosis that includes imaging and histology. Increased clinical awareness of mesenchymal hamartoma in infants may help to guide the approach to the correct diagnosis and prevent unnecessarily radical treatment for this benign condition.

Sudden Death Due to Recent Hemorrhage From an Intrathoracic Chronic Expanding Hematoma.

Chronic expanding hematoma (CEH) is a rare disease that can develop in any region of the body, but it most frequently develops in the thorax. When intrathoracic CEH is left untreated, gradually expanding hematoma can be life-threatening, leading to respiratory failure or hemoptysis. We encountered an 89-year-old man with cardiopulmonary arrest on arrival. He had been healthy, and it was unclear whether CEH had previously been detected. A very large mass was observed on chest computed tomography (CT), but the cause of death could not be determined. In the autopsy, this mass was identified as CEH and no malignant findings were noted. A fresh hemorrhage had occurred in the hematoma and perforated the bronchial lumen, which caused airway obstruction/asphyxia and resulted in sudden death. CEH should be suspected when a very large tumorous lesion occupying the entire hemithorax is observed on chest imaging, and it is important to recognize that sudden death can occur in the natural course of CEH.

Management of primary spontaneous pneumothorax: a review.

Primary spontaneous pneumothorax is a common problem faced by doctors in medical practice. It is a significant global health problem affecting adolescent and young adults. This article will review the etiopathology, diagnosis and current management guidelines. It aims to improve clinical practice and compliance to the complexities of procedures involved in management.

Thoracic calcifications on magnetic resonance imaging: correlations with computed tomography / Calcificações torácicas na ressonância magnética: correlações com a tomografia computadorizada

ABSTRACT Objective: To identify the characteristics of thoracic calcifications on magnetic resonance (MR) imaging, as well as correlations between MR imaging and CT findings. Methods: This was a retrospective study including data on 62 patients undergoing CT scans and MR imaging of the chest at any of seven hospitals in the Brazilian states of Rio Grande do Sul, São Paulo, and Rio de Janeiro between March of 2014 and June of 2016 and presenting with calcifications on CT scans. T1- and T2-weighted MR images (T1- and T2-WIs) were semiquantitatively analyzed, and the lesion-to-muscle signal intensity ratio (LMSIR) was estimated. Differences between neoplastic and non-neoplastic lesions were analyzed. Results: Eighty-four calcified lesions were analyzed. Mean lesion density on CT was 367 ± 435 HU. Median LMSIRs on T1- and T2-WIs were 0.4 (interquartile range [IQR], 0.1-0.7) and 0.2 (IQR, 0.0-0.7), respectively. Most of the lesions were hypointense on T1- and T2-WIs (n = 52 [61.9%] and n = 39 [46.4%], respectively). In addition, 19 (22.6%) were undetectable on T1-WIs (LMSIR = 0) and 36 (42.9%) were undetectable on T2-WIs (LMSIR = 0). Finally, 15.5% were hyperintense on T1-WIs and 9.5% were hyperintense on T2-WIs. Median LMSIR was significantly higher for neoplastic lesions than for non-neoplastic lesions. There was a very weak and statistically insignificant negative correlation between lesion density on CT and the following variables: signal intensity on T1-WIs, LMSIR on T1-WIs, and signal intensity on T2-WIs (r = −0.13, p = 0.24; r = −0.18, p = 0.10; and r = −0.16, p = 0.16, respectively). Lesion density on CT was weakly but significantly correlated with LMSIR on T2-WIs (r = −0.29, p < 0.05). Conclusions: Thoracic calcifications have variable signal intensity on T1- and T2-weighted MR images, sometimes appearing hyperintense. Lesion density on CT appears to correlate negatively with lesion signal intensity on MR images.

RESUMO Objetivo: Identificar as características das calcificações torácicas na ressonância magnética (RM) e as correlações entre os achados de RM e TC. Métodos: Estudo retrospectivo no qual foram analisados dados referentes a 62 pacientes que foram submetidos a TC e RM de tórax em sete hospitais nos estados do Rio Grande do Sul, São Paulo e Rio de Janeiro entre março de 2014 e junho de 2016 e que apresentaram calcificações na TC. As imagens de RM ponderadas em T1 e T2 (doravante denominadas T1 e T2) foram analisadas semiquantitativamente, e a razão entre a intensidade do sinal da lesão e do músculo (LMSIR, do inglês lesion-to-muscle signal intensity ratio) foi estimada. Diferenças entre lesões neoplásicas e não neoplásicas foram analisadas. Resultados: Foram analisadas 84 lesões calcificadas. A média de densidade das lesões na TC foi de 367 ± 435 UH. A mediana da LMSIR foi de 0,4 [intervalo interquartil (II): 0,1-0,7] em T1 e 0,2 (II: 0,0-0,7) em T2. A maioria das lesões mostrou-se hipointensa em T1 e T2 [n = 52 (61,9%) e n = 39 (46,4%), respectivamente]. Além disso, 19 (22,6%) foram indetectáveis em T1 (LMSIR = 0) e 36 (42,9%) foram indetectáveis em T2 (LMSIR = 0). Finalmente, 15,5% mostraram-se hiperintensas em T1 e 9,5% mostraram-se hiperintensas em T2. A mediana da LMSIR foi significativamente maior nas lesões neoplásicas do que nas não neoplásicas. Houve uma correlação negativa muito fraca e estatisticamente insignificante entre a densidade das lesões na TC e as seguintes variáveis: intensidade do sinal em T1, LMSIR em T1 e intensidade do sinal em T2 (r = −0,13, p = 0,24; r = −0,18, p = 0,10 e r = −0,16, p = 0,16, respectivamente). A densidade das lesões na TC apresentou correlação fraca, porém significativa com a LMSIR em T2 (r = −0,29, p < 0,05). Conclusões: As calcificações torácicas apresentam intensidade de sinal variável em T1 e T2; em alguns casos, mostram-se hiperintensas. A densidade da lesão na TC aparentemente correlaciona-se negativamente com a intensidade do sinal da lesão na RM.

Human pericardial proteoglycan 4 (lubricin): Implications for postcardiotomy intrathoracic adhesion formation.

OBJECTIVE: Intrapericardial fibrous adhesions increase the risk of sternal reentry. Proteoglycan 4/lubricin (PRG4) is a mucin-like glycoprotein that lubricates tissue compartments and prevents inflammation. We characterized PRG4 expression in human pericardium and examined its effects in vitro on human cardiac myofibroblast fibrotic activity and in vivo as a measure of its therapeutic potential to prevent adhesions. METHODS: Full-length PRG4 expression was determined using Western blot analysis and amplified luminescent proximity homogeneous assay in human pericardial tissues obtained at cardiotomy. The in vitro effects of PRG4 were investigated on human cardiac myofibroblasts for cell adhesion, collagen gel contraction, and cell-mediated extracellular matrix remodeling. The influence of PRG4 on pericardial homeostasis was determined in a chronic porcine animal model. RESULTS: PRG4 is expressed in human pericardial fluid and colocalized with pericardial mesothelial cells. Recombinant human PRG4 prevented human cardiac myofibroblast attachment and reduced myofibroblast activity assessed using collagen gel contraction assay (64.6% ± 8.1% vs 47.1% ± 6.8%; P = .02). Using a microgel assay, human cardiac myofibroblast mediated collagen fiber remodeling was attenuated by PRG4 (1.17 ± 0.03 vs 0.90 ± 0.05; P = .002). In vivo, removal of pericardial fluid alone induced severe intrapericardial adhesion formation, tissue thickening, and inflammatory fluid collections. Restoration of intrapericardial PRG4 was protective against fibrous adhesions and preserved the pericardial space. CONCLUSIONS: For the first time, we show that PRG4 is expressed in human pericardial fluid and regulates local fibrotic myofibroblast activity. Loss of PRG4-enriched pericardial fluid after cardiotomy might induce adhesion formation. Therapeutic restoration of intrapericardial PRG4 might prevent fibrous/inflammatory adhesions and reduce the risk of sternal reentry.