Lung adenocarcinoma associated with cystic airspaces

To the Editor, Lung cancer associated with cystic airspaces is a group of uncommon lung malignant lesions that are easy to misdiagnose even though the use of computed tomography (CT) has been more common for lung cancer screening in the clinic. The incidence of this lesion has been reported at 0.5%–3.7% in different studies. Up to 80% of patients was of pulmonary adenocarcinomas and most patients had a history of smoking. Here, we reported a case of lung adenocarcinoma associated with cystic airspace developed at least 7 years progression from one purely thin‐walled lung cavity closing to the pleura on CT images in a 53‐year‐old man without a smoking history. Histopathology revealed the thickened wall of the cystic airspace was lung adenocarcinoma with extensive papillary and micropapillary patterns and psammoma bodies. A 53‐year‐old asymptomatic male without a smoking history has had a physical examination every 1–2 years since 2013. The patient has no history of asbestos and dust exposure. In December 2013, a local thin‐wall air cavity in the right lower lobe close to the pleura (Figure 1A) and nodular thickening of the bilateral pleura with partial calcification (data not shown) were found for the first time on his CT scan. Five months later, this patient underwent a chest CT examination again and there was no obvious change compared to the CT scan in 2013 (Figure 1B). After that, he did a chest CT examination every 1–2 years. No obvious radiological change was found (Figure 1C,D). However, in Oct 2018, a nonsolid nodule was found extruding from the local wall of the cystic airspace (Figure 1E), but these changes did not attract the attention of radiologists and physicians. Two years later, this nodule increased in size, and the wall of the cystic airspace thickened, which was considered the manifestation of lung cancer (Figure 1F). From 2013 to 2020, this patient had no discomfort. In December 2020, he was administrated to our hospital for further diagnosis and treatment. A physical examination of this case showed no obvious abnormality. Axial CT images in a lung window setting showed a thicken‐walled cystic space with exophytic solid nodules along the cyst wall (Figure 1G). A soft tissue nodule was seen in the mediastinal window (Figure 1H). An irregular thick‐walled cavity with local solid nodule formation after three‐dimensional reconstruction can be easily detected (Figure 1I). Bilateral pleurae showed irregular thickening and multiple small nodules and calcifications (Figure 1J). After exclusion of extrathoracic malignancies by examination of brain CT scan and single‐photon emission computed tomography (SPECT) whole bone scan, resection of the cyst with nodules was performed and the malignant tumor was reported via intraoperative frozen tissue pathology. So, a right lower lobectomy with lymph node dissection was subsequently performed. Postoperative pathology confirmed that there were no metastases in the margins, broken ends of the bronchus, pleural, and peripheral lymph nodes (2–4 group [0/1], 7 group [0/8], 8 group [0/1], 11 group [0/4]). The resection specimen showed that the size of the cyst is about 2.0 × 1.5 × 1.0 cm. Histopathology examination revealed the nodule extruding from the local wall of the cystic airspace was pulmonary adenocarcinoma with extensive papillary and micropapillary patterns and psammoma bodies (Figure 2A). Hematoxylin and eosin (HE) staining of tumor specimen suggested that there was no defined lining between the tumor tissue and the cavity (Figure 2A). Immunohistochemical staining showed the tumor cells were strongly positive for thyroid transcription factor 1 (TTF‐1) (Figure 2B) and NapsinA (Figure 2C), positive for cytokeratin (CK) 19, Galectin 3, Cyclin D1, carcino‐ embryonic antigen (CEA) and CK7 (data not shown), while negative for Tg (Figure 2D), CDX2, P40, CK5/6 and CK20 (data not shown). The ki‐67 index was about 20% revealing slower cell proliferation (data not shown). The tumor cells were also negative for programmed cell death ligand 1 (PD‐L1) expression with tumor cell proportion score (TPS) < 1% and combined positive score (CPS) = 10 (Figure 2E). The size of one resected grayish‐yellow pleural nodule was about 0.6 cm× 0.4 cm in size and was a pure calcific nodule without metastasis of pulmonary adenocarcinoma by HE staining (Figure 2F). A lung adenocarcinoma staged at pT1cN0M0 (Stage IA3) was diagnosed for this case. Epidermal growth factor receptor (EGFR) mutations and anaplastic lymphoma kinase (ALK) rearrangements were not found