Genetic and immunohistochemical analyses of ciliated muconodular papillary tumors of the lung: A report of five cases

Bronchiolar adenoma/ciliated muconodular papillary tumor complicated by lymphoid interstitial pneumonia in a patient with Sjögren's disease: A case report and systematic review

Bronchiolar adenoma (BA)/ciliated muconodular papillary tumor (CMPT) is a rare pulmonary neoplasm, with less than 150 cases documented in the literature. We report a unique case of BA/CMPT complicated by lymphoid interstitial pneumonia (LIP) in a 55-year-old male with Sjögren's disease. This is the first documented instance of such a comorbidity. Through a systematic review of PubMed, we also summarize the demographic, clinical, radiological, histopathological, and treatment characteristics of CMPT.

Clinicopathological Analysis of Bronchiolar Adenoma Lined Purely by Mucinous Luminal Cells

Bronchiolar adenoma (BA) is a rare lung tumor that has recently been clearly named, including the previous ciliated muconodular papillary tumor (CMPT) and the so-called nonclassical CMPT. The most prominent histological feature of BA is a double-layer cell structure composed of a continuous basal cell layer and a luminal cell layer. BA lined purely by mucinous luminal cells is very rare, and only one case has been reported in the English literature. This type of BA can easily be misdiagnosed as early mucinous adenocarcinoma. This article analyzes the clinicopathological characteristics of a newly discovered case of BA lined purely by mucinous luminal cells and fully integrated with the literatures.

Multiple bronchiolar adenomas/ciliated muconodular papillary tumors of the bilateral lung with tumor budding and potential malignant transformation into squamous cell carcinoma: a case report and literature review

Background

Bronchiolar adenoma (BA)/ciliated muconodular papillary tumor (CMPT) is a rare lung tumor characterized by ciliated, mucous and basal cells. Recently, some cases of driver mutations or malignant transformations have been reported. However, the nature of BA/CMPT remains controversial. Here, we report a case of bilateral pulmonary multiple BAs with tumor budding and squamous metaplasia.

Case Description

A 55-year-old man presented with multiple small nodules in the lower lobes of the bilateral lungs on physical examination 7 years prior. During the past 3 years of regular follow-up, some nodules had slightly enlarged. Because the nodules were mostly solid, the patient underwent video-assisted thoracoscopic segmentectomy of the left lower lung. A postoperative pathological diagnosis of BA was made. In all lesions, the fusion and mutation of major driver genes were not detected by next-generation sequencing (NGS). No recurrence or metastasis was observed after 37 months of follow-up. Notably, all five resected lesions were BA/CMPT, and one lesion was accompanied by squamous metaplasia and tumor budding.

Conclusions

Our report found that BA/CMPT with squamous metaplasia and tumor budding has the potential to transform into lung squamous cell carcinoma, expanding its connection with malignant transformation. Smoking may be one of the risk factors. We also found that BA/CMPT can be multiple lesions rather than a solitary lesion.

Malignant transformation of pulmonary bronchiolar adenoma into mucinous adenocarcinoma: A case report

BACKGROUND

Bronchiolar adenoma (BA) and ciliated muconodular papillary tumor are rare tumors that have bilayered cell proliferation and continuous expression of p40 and CK5/6 in the basal cell layer. Diagnosis is difficult because of the limited knowledge of these tumors and their morphological similarities to malignant tumors, including invasive mucinous adenocarcinoma, especially based on the histopathology of intraoperative frozen sections. These tumors are now considered to be benign neoplasms, with malignant transformation reported in only a few cases.

CASE SUMMARY

A 57-year-old woman presented with a 17.0 mm × 7.0 mm nodule in the lower lobe of the left lung. Hematoxylin-eosin staining and immunohistochemistry of a surgical specimen were performed. The tumor consisted of a BA area and a mucinous adenocarcinoma (MA) area. In the BA area, the tumor had a bilayered structure of luminal cells and basal cells. The basal cells were positive for CK5/6 and p40, but the MA area was negative for these biomarkers. The Ki-67 proliferation index was low (1%-2%). The patient was diagnosed with BA accompanied by MA, and had a favorable outcome.

CONCLUSION

The present study indicated that BA may be carcinogenic, and suggests that clinicians should be aware of its potential for malignant transformation.

Comprehensive clinicopathological characteristics and mucin core protein expression profiles of bronchiolar adenoma

AIMS

Bronchiolar adenoma (BA) is a novel entity in the 2021 WHO classification of lung tumours. The expression profile of mucin core proteins in BAs is not clear. The aim of this study was to clarify the expression profiles of mucins and to validate the clinicopathologic and molecular features of BAs.

METHODS AND RESULTS

We examined the clinicopathological, immunohistochemical, and molecular features of 20 BAs. Our cohort comprised 10 proximal and 10 distal BAs. Only seven of 18 patients (39%) were accurately diagnosed with BA at the time of intraoperative consultation. The frequent genetic alterations were BRAF V600E (35%) and KRAS (30%) mutations, which were mutually exclusive. The expression of MUC1, MUC4, and MUC5B was observed in all cases and that of MUC5AC and MUC6 was observed in nine (45%) and five (25%) cases, respectively. MUC4 was diffusely expressed in 18 cases. In contrast, MUC1, MUC5AC, MUC5B, and MUC6 displayed a patchy expression pattern. These expression patterns were similar to that of bronchiolar epithelium in normal lung tissue. In addition, overexpression of MUC1 and MUC4 on the entire cell surface was not observed in any of the BAs, suggesting their benign nature.

CONCLUSION

BA commonly exhibits diffuse MUC4 and patchy MUC1 and MUC5B expression. Its unique expression pattern is probably attributed to mucin expression specific to the bronchiolar epithelium. These results confirm the clinicopathologic and molecular characteristics of BA, including the difficulty in intraoperative frozen section diagnosis and the broad morphologic spectrum of BA derived from the bronchiolar epithelium.

Pulmonary Sialadenoma Papilliferum and Its Mimics: What You Need to Know

Pulmonary salivary gland-type tumors (SGT) represent a small but distinct group of primary lung neoplasms. These types of tumors originate from the submucosal bronchial glands of the tracheobronchial tree. Pulmonary SGTs differ greatly in the incidence of individual tumors from salivary gland tumors of the head and neck. Additionally, the vast majority of pulmonary SGT are malignant. Recently, pathologic diagnosis has significantly improved with the application of molecular diagnostic technologies. However, the current knowledge of benign SGTs is limited; moreover, tumor diversity and overlapping morphological features of SGT represent diagnostic challenges such as correct tumor categorization and their accurate differentiation from malignant lesions. Compounding this inherent difficulty has been the recent introduction of new variants, including sialadenoma papilliferum (SP). Pulmonary SP is very rare, with limited reports available, and most of the initial diagnoses rendered so far were incorrect, resulting in inappropriate treatment. Several cases of SP have recently been reported. This review will serve to update practicing pathologists on the morphology, immunophenotype, and molecular characteristics of SP and its mimics.

Mucin distribution in bronchiolar adenoma/ciliated muconodular papillary tumor reveals organoid differentiation simulating the normal lung

Bronchiolar adenoma/ciliated muconodular papillary tumor is a lung neoplasm exhibiting various degrees of proximal and distal bronchiolar differentiation. Here, we evaluated distribution of MUC5AC and MUC5B in bronchiolar adenoma/ciliated muconodular papillary tumor for comparison with that seen in normal respiratory tract. In normal respiratory tract, MUC5AC was mainly distributed in large bronchi, while MUC5B was distributed in bronchi, bronchioles, and submucosal glands. In bronchiolar adenoma/ciliated muconodular papillary tumor, MUC5AC was primarily distributed in luminal cells of large airspaces, and MUC5B was distributed in luminal cells of small airspaces and mucinous glands, in addition to large airspaces, regardless of distal or proximal differentiation. In particular, MUC5B was distributed in non-mucinous club and ciliated cells in both the normal respiratory tract and bronchiolar adenoma/ciliated muconodular papillary tumor. These results indicate that MUC5AC and MUC5B distribution in bronchiolar adenoma/ciliated muconodular papillary tumor is similar to that seen in normal respiratory tract, suggestive of organoid differentiation simulating the normal lung.

[Diagnosis and treatment of benign lung tumors]

Benign lung tumors account 2-12% of all lung neoplasms. The classification of lung tumors, adopted by the World Health Organization in 2015, is reported with a detailed indication of all changes based on immunohistochemical and genetic studies. Diagnosis with computed tomography, dynamic and perfusion computed tomography, virtual bronchoscopy and positron emission tomography is described. These methods ensure 94-98% sensitivity for differentiation with malignancies. CT and ultrasound signs of benign tumors are presented. Surgical strategy for newly diagnosed nodes in the lungs is analyzed depending on their dimensions and risk factors. It was shown that comprehensive examination with possible surgical verification of the diagnosis is necessary for nodes over 6 mm and moderate-to-high risk factors. The authors describe argon plasma and laser destruction, bronchoplastic procedures for central benign tumors, thoracoscopy for peripheral neoplasms. One can conclude that high-tech methods of radiological and nuclear diagnosis are valuable to determine benign neoplasms and their dimensions with a high degree of reliability. Endoscopic and thoracoscopic procedures are successfully used for benign tumors.

Primary ciliated muconodular papillary tumor: A rare pulmonary disease and literature review of 65 cases

A ciliated muconodular papillary tumor (CMPT) or bronchiolar adenoma (BA) is a rather rare and unique type of lung tumor characterized by tripartite cellular components with a papillary-predominant structure including ciliated columnar cells, mucinous cells, and basal cells. Here, we present the case of a 64-year-old woman who was diagnosed with CMPT in our center. In addition to reporting the clinicopathological characteristics of this case, we also conducted whole exome sequencing (WES) to explore the underlying mechanism. According to current evidence, CMPTs tends to be benign or of low grade malignancy. However, this requires further validation.