Pulmonary sclerosing pneumocytoma: clinical features and prognosis

Single-cell transcriptome analysis reveals two subtypes of tumor cells of sclerosing pneumocytoma with distinct molecular features and clinical implications

Pulmonary sclerosing pneumocytoma (PSP) is a rare, distinctive benign lung adenoma of pneumocyte origin. Despite its rarity, the tumor's unique cellular morphology has sparked ongoing debates regarding the origin of its constituent cells. This study aimed to elucidate the molecular features of PSP tumor cells and enhance our understanding of the cellular processes contributing to PSP formation and biological behavior. Tissue samples from PSP and corresponding normal lung tissues (n = 4) were collected. We employed single-cell RNA sequencing and microarray-based spatial transcriptomic analyses to identify cell types and investigate their transcriptomes, with a focus on transcription factors, enriched gene expression, and single-cell trajectory evaluations. Our analysis identified two types of tumor cells: mesenchymal epithelial dual phenotype cells (MEDPs) and a distinct subpopulation of type II alveolar epithelial cells exhibiting characteristics slightly reminiscent of type I alveolar epithelial cells (AT2Cs), corresponding to histological round stromal cells and surface cuboidal cells, respectively. MEDPs displayed weak alveolar epithelial differentiation but strong collagen production capabilities, as indicated by the expression of both TTF-1 and vimentin. These cells played a pivotal role in forming the solid and sclerotic areas of PSP. Moreover, MEDPs exhibited a pronounced propensity for epithelial-mesenchymal transition, suggesting a greater potential for metastasis compared to AT2Cs. The capillary endothelial cells of PSP displayed notable diversity. Overall, this study provides, for the first time, a comprehensive mapping of the single-cell transcriptome profile of PSP. Our findings delineate two distinct subtypes of tumor cells, MEDPs and AT2Cs, each with its own biological characteristics and spatial distribution. A deeper understanding of these cell types promises insights into the histology and biological behaviors of this rare tumor.

Navigating the diagnostic maze: the challenge of sclerosing pneumocytoma in frozen sections

Pulmonary Sclerosing Pneumocytoma (PSP) represents a rare benign tumor that exhibits a predisposition towards females. Often asymptomatic, its identification usually occurs incidentally through imaging modalities. Histologically, PSP demonstrates features consistent with pneumocytic differentiation and possesses a dual-cell population. However, in rare instances it may demonstrate pleural invasion or lymph node metastasis. Diagnosing PSP through small biopsy or frozen section presents considerable challenges attributed to its heterogeneous growth patterns and striking similarity to well-differentiated pulmonary adenocarcinoma. We report a case of PSP in a 57-year-old female smoker, presenting as a slow-growing 2.5 cm mass that recently exhibited enlargement, as noted on computed tomography (CT) scan. The recommendation for excising the mass prompted the patient to undergo a right robotic-assisted thoracoscopic procedure, which entailed wedge resection of the right lower lobe and an intraoperative consultation. A completion right lower lobectomy was performed, accompanied by lymph node dissection, following a frozen section diagnosis indicating at least adenocarcinoma in situ. The permanent section revealed bland cuboidal cells lining papillary and sclerotic areas, with occasional atypical features such as prominent nucleoli and scattered mitotic figures. Adjacent foci of atypical adenomatous hyperplasia (AAH) were noted. Immunohistochemical (IHC) staining revealed positive Napsin A, keratin AE1/3, and CK7 in surface cells but not in round cells. Both EMA and TTF1 immunostains highlighted surface cells and scattered round cells. Elastic stain highlighted visceral pleural involvement. The combined morphology and immunoprofile supported the diagnosis of PSP. This case underscores the critical importance of accurately diagnosing slow-growing pulmonary nodules, which are increasingly detected by the widespread use of imaging for various medical conditions.

Pulmonary sclerosing pneumocytoma - approaching a solitary pulmonary nodule and the limitations of risk prediction models

Our case is an asymptomatic, non-smoking, East Asian woman in her 40s presenting with a solitary pulmonary nodule (SPN). On imaging, the 1.7 cm solid SPN located in the left upper lobe, was rounded in morphology and moderately fluorodeoxyglucose avid. The clinical pretest probability of malignancy assessed by risk prediction models such as Brock (19.1%), Mayo Clinic (56.2%) and Herder (51.4%) was discordant. She underwent a percutaneous CT-guided needle biopsy, establishing a diagnosis of pulmonary sclerosing pneumocytoma (PSP). PSP is a rare benign lung neoplasm with indolent growth characteristics that has been described predominantly in non-smoking women. Our case illustrates the limitations of applying existing risk prediction models in Asia where the epidemiology and biology of lung cancer differ significantly from the Caucasian derivation cohorts. Additionally, the risk models do not account for tuberculosis, which is endemic in Asia and can mimic malignancy. Non-surgical lung biopsy remains useful in minimising unnecessary thoracotomy.

Giant pulmonary sclerosing pneumocytoma with potentially malignant biological behavior: a case report and literature review

Background

Pulmonary sclerosing pneumocytoma (PSP) is a rare benign lung tumor which generally presents as a solitary pulmonary nodule in middle-aged females. However, the PSP in some patients exhibits potentially malignant biological behavior, with recurrence and lymphatic or distant metastasis being observed.

Case Description

We encountered a case of a 46-year-old female with an inordinately massive tumor 9.5 cm in diameter and a relatively high Ki-67 proliferation rate. Fine needle aspiration (FNA) played a significant but limited role in the preoperative diagnosis: the computed tomography (CT)-guided lung puncture biopsy was consistent with the typical pathology of PSP; however, endobronchial ultrasound-guided transbronchial lung biopsy (EBUS-TBLB) could not provide a definitive diagnosis. The patient ultimately underwent thoracoscopic resection and mediastinal lymph node dissection. Here, we provide a review of the literature on patients with PSP with malignant biological behavior to raise awareness of the malignant potential of PSP and describe our experience to inform future management.

Conclusions

PSP lacks specificity in its clinical and radiological characteristics and has complex pathological manifestations. FNA is valuable in the diagnosis and differential diagnosis of PSP but involves the risk of misdiagnosis or missed diagnosis. Additionally, we believe that the accepted benign features of PSP need to be updated and that the potential malignant features of PSP should be carefully monitored. Surgical resection is curative but strict follow-up is crucial.

[Recent Advances and Controversies in Minute Pulmonary Meningothelial-like Nodules]

Minute pulmonary meningothelial-like nodules (MPMNs) are benign small lesions in the lungs, with similar pathological characteristics to the meningeal epithelium. MPMNs have similar imaging manifestations to malignant tumors, which can lead to misdiagnosis in clinical practice. There is no consensus on the pathogenesis of MPMNs, with some suggest that MPMNs derive from reactive proliferation, while others suggest that MPMNs share a common origin and molecular mechanism with meningiomas in the central nervous system. Understanding the characteristics of MPMNs and studying their pathogenesis will help improve the understanding and diagnosis of MPMNs. In this article, we reviewed the clinical, pathological, imaging characteristics, differential diagnosis and pathogenesis of MPMNs. We also analyze the existing research advances regarding the pathogenesis and propose prospects for further research.
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An advanced molecular medicine case report of a rare human tumor using genomics, pathomics, and radiomics

Background: Pulmonary Sclerosing Pneumocytoma (PSP) is a rare tumor of the lung with a low malignant potential that primarily affects females. Initial studies of PSP focused primarily on analyzing features uncovered using conventional X-ray or CT imaging. In recent years, because of the widespread use of next-generation sequencing (NGS), the study of PSP at the molecular-level has emerged. Methods: Analytical approaches involving genomics, radiomics, and pathomics were performed. Genomics studies involved both DNA and RNA analyses. DNA analyses included the patient's tumor and germline tissues and involved targeted panel sequencing and copy number analyses. RNA analyses included tumor and adjacent normal tissues and involved studies covering expressed mutations, differential gene expression, gene fusions and molecular pathways. Radiomics approaches were utilized on clinical imaging studies and pathomics techniques were applied to tumor whole slide images. Results: A comprehensive molecular profiling endeavor involving over 50 genomic analyses corresponding to 16 sequencing datasets of this rare neoplasm of the lung were generated along with detailed radiomic and pathomic analyses to reveal insights into the etiology and molecular behavior of the patient's tumor. Driving mutations (AKT1) and compromised tumor suppression pathways (TP53) were revealed. To ensure the accuracy and reproducibility of this study, a software infrastructure and methodology known as NPARS, which encapsulates NGS and associated data, open-source software libraries and tools including versions, and reporting features for large and complex genomic studies was used. Conclusion: Moving beyond descriptive analyses towards more functional understandings of tumor etiology, behavior, and improved therapeutic predictability requires a spectrum of quantitative molecular medicine approaches and integrations. To-date this is the most comprehensive study of a patient with PSP, which is a rare tumor of the lung. Detailed radiomic, pathomic and genomic molecular profiling approaches were performed to reveal insights regarding the etiology and molecular behavior. In the event of recurrence, a rational therapy plan is proposed based on the uncovered molecular findings.

Treatment and post-operative follow-up of pulmonary sclerosing pneumocytoma: A case report

Introduction and importance

Pulmonary sclerosing pneumocytoma (PSP) is a rare tumor thought to originate from respiratory epithelial cells. It is usually benign, but may rarely metastasize to lymph nodes. Surgeons face unique challenges in diagnosis and management of this condition, and ideal surgical management is yet to be established.

Case presentation

48-year-old woman with a 7 × 7 mm pulmonary lesion discovered incidentally on computerized tomography (CT) imaging, which grew to 9 mm over the following year. Seven years later, follow-up imaging revealed that the mass had grown to 1.3 cm in largest dimension. Surgery was recommended and the mass was resected via a right video-assisted thoracic surgery (VATS) middle lobectomy with mediastinal lymph node dissection. All lymph nodes were negative and the patient's postoperative course was unremarkable.

Clinical discussion

There are few evidence-based guidelines available on the treatment and postoperative surveillance of PSP. Research has shown comparable recurrence-free survival rates for sublobar resection and lobectomy, though recurrence can occur, especially following sublobar resection in larger or more centrally-located tumors. In absence of established guidelines, it was decided to follow this patient according to NCCN guidelines for surveillance of early-stage non-small cell lung cancer due to potential risk of recurrence.

Conclusion

This case report adds to the limited literature on PSP and depicts a possible treatment and postoperative follow-up plan. Right VATS middle lobectomy can effectively treat some cases of central PSP. In absence of established guidelines for postoperative follow-up of PSP, NCCN guidelines may outline one possible strategy for postoperative management.