Cyst-related primary lung malignancies: an important and relatively unknown imaging appearance of (early) lung cancer

Abstract

@ERSpublications Primary lung cancer can present as cystic airspace with an associated solid component, and seems to be a relatively common imaging phenotype of (early) lung cancer. This morphology is often not recognised and misinterpreted, leading to diagnostic delay.ABSTRACT It is well known that lung cancer can manifest itself in imaging as solid and subsolid nodules or masses. However, in this era of increased computed tomography use another morphological computed tomography appearance of lung cancer is increasingly being recognised, presenting as a malignancy in relation to cystic airspaces. Despite the fact that it seems to be a relatively common finding in daily practice, literature on this entity is scarce and presumably the overall awareness is limited. This can lead to misinterpretation and delay in diagnosis and, therefore, increased awareness is urgently needed. This review aims to illustrate the imaging appearances of cyst-related primary lung malignancies, demonstrate its mimickers and potential pitfalls, and discuss the clinical implications based on the available literature and our own experience in four different hospitals. Cyst-related primary lung malignanciesManagement guidelines for indeterminate small solid pulmonary lesions are available for both clinical use and in the screening setting [1,2]. This has led to more (serial) computed tomography (CT) imaging and more structured and uniform interpretation and surveillance of pulmonary nodules. Over a decade ago it emerged that beside solid nodules and masses a second group of morphologically distinct lung cancers existed; subsolid pulmonary malignancies. Instead of a solid nodular lung lesion, these present as persistent pure ground-glass or part-solid pulmonary nodules. This distinction is highly relevant in daily practice as the behaviour of subsolid lesions differs significantly from that of solid lesions, being more commonly adenocarcinomas and showing slower growth but higher malignancy rates than solid nodules [3,4]. However, it is now increasingly recognised that primary lung cancer does not always appear as either a solid or subsolid nodule on imaging. An important and presumably under recognised morphology of (early) lung cancer is the cyst-related primary lung malignancy. Terminology used in prior literature includes "( peri)cystic adenocarcinoma" and "cancers in association with cystic airspaces". The entity has been reported on in a few smaller original studies [5][6][7][8][9], which were recently summarised in an imaging review paper [10]. In total, less than 100 cases have been reported, originating from both a screening and a

Lung cancer associated with cystic airspaces: a new radiological presentation of lung cancer

“…A type IV lesion is a multilocular cystic lesion with interposed solid tissue or a ground-glass component ( Figure 1 ). 3 - 5 Differences among these types, as well as their growth rate, biological behavior, and prognosis, have yet to be determined.…”

“…These lesions were previously thought to arise from congenital cysts; however, recent studies have failed to find histopathological evidence to support that theory. 5 Currently, the two most accepted evidence-based theories are that there is a pre-existing cystic airspace in which malignancy develops or that there is formation of a cyst by a “check-valve mechanism” due to a small malignant lesion that only becomes visible after growth. 2 , 5 …”

“…Cavitation is usually due to post-treatment necrosis, internal cyst formation, or internal desquamation of tumor cells with subsequent liquefaction. 5 The most common histological type of cavitary lung cancer is non-small cell lung carcinoma, especially squamous cell carcinoma, whereas the most common histological type of cystic/pericystic lung cancer is adenocarcinoma. 2 , 5 …”

“…Cystic/pericystic cancer can be misdiagnosed as a severe form of emphysematous disease, distal airway enlargement, or fibrosis. 5 …”

Giant Secondary Overgrowth of Type-1 Pulmonary Cystic Airway Malformation Upon Development of Anaplastic Lymphoma Kinase–Rearranged Adenocarcinoma

“…15,16 The presence of disarrayed elements of bronchial origin in the cyst wall, along with clinical and laboratory findings and the lack of additional imaging alterations were all in keeping with an ALK-positive ADC-arising in type 1 PCAM and allowed other congenital or acquired cystic changes of the lung, either neoplastic or nonneoplastic, to be consistently ruled out (e.g., bronchiectasis, intra-lobar sequestration, mesenchymal cystic hamartoma, bronchogenic cyst, thin-walled emphysematous cyst, parenchymal cystic remodeling by perivascular epithelioid cells in lymphangioleiomyomatosis, tuberculosis and other fibro-inflammatory cysts, interstitial lung disease, vasculitis, and common lung cancer cavitation). 1,[15][16][17][18] Re-evaluation of two unrelated chest radiographs dating back to 9 and 5 years before failed to show any recognizable cyst in the same anatomical region of the right lung, confirming a giant secondary overgrowth of a small-sized type 1 PCAM. To this regard, the issue of lung cancer arising within pre-existing cysts or developing along with cyst-forming parenchymal structural changes is clinically emerging especially when dealing with early lung cancer screening action projects.…”