Clinical and radiological features of NSNs
We identified 62 patients who were diagnosed at our Institutions with lung malignant NSNs. Of them, 26 were females (41.9%) and 36 (58.1%) males; the mean age at diagnosis was 69, 35 years. Thirty-four patients were never smokers, while 14 were past smokers and only 4 was a current smoker. Smoking history was unknown in 9 cases. Twenty-five (40.3%) out of the 62 evaluated patients referred a previous diagnosis of cancer and were in remission at time of enrolment; one patient was assuming immunosuppressive drugs due to previous heart transplantation. Forty out of the 62 lesions were in the right lung, 30 in the upper lobe, 8 in the lower and 2 in the middle one, respectively. Seventeen were in the left lung, 10 in the upper lobe, 6 in the lower and 1 in the lingula, respectively. Overall, in 26 cases consisted of basal parenchymal lesion lesions, more difficult to be approached. Based on nodule localization, the procedural approach was posterior or anterior. Most lesions occurred peripherally within the lung parenchyma (48 patients, 77.4%); while 13 cases featured peri-mediastinal nodules. Twenty-nine (46.77%) of the analysed nodules displayed a contact with the pleural layer. Of them, 4 nodules grew in contact with the fissure, in 16 a small peduncle was detected whereas the remaining 9 featured a wide interface with the visceral pleura. The vast majority of nodules displayed a round/ovalar shape with irregular margins. The aerated lung run of the needle was between 1 mm and 60 mm respectively, the minimal distance from middle-large veins and arteries (segmental, lobar and main pulmonary) was of 3 mm. In 37 (59.6%) cases, nodules had mixed or semi-solid appearance, the remaining were pure non-solid. All but seven lesions were small, displaying a diameter ≤ 3 cm; in only two case the diameter was of 5 cm and 6 cm, respectively.
Thirty-seven out of all the patients underwent transthoracic FNA TC-guided biopsy (needle: 24 gauge) leading to a diagnosis of NSCLC (ADC) in 31; in six cases, the diagnosis was inconclusive (suspicious for neoplastic cells); in 3 cases out of the latter a second FNA was performed, leading to a conclusive ADC diagnosis. In 25 patients transthoracic TC-guided CNB (needle: 18 gauge) was performed and allowed the diagnosis of NSCLC (ADC) in all cases.
The diagnosis of lung ADC was reached in all cases on the sole basis of cell morphology and architecture on H&E stained slides derived from both FNA and CNB tissue samples; immunohistochemical staining was required in 3 cases to exclude metastasis form a previous extrapulmonary ADC.
Overall fourteen out of the 62 cases early minor complications (22.5%). In detail, among the 37 nodules biopsied through FNA, minor complications aroused in 6 cases (9.6%), one patient presented mild haemoptysis rapidly solved after tranexamic acid infusion; whereas in the remaining five a small pneumothorax could be demonstrated after the procedure. In the cohort of the 25 nodules reached through by CNB, 8 (12.8%) cases presented early small pneumothorax demonstrated after the procedure. Major complications regarded the occurrence of complete pneumothorax which was managed by chest tube insertion and drainage in one case and in two case in the cohort of FNA and CNB, respectively. No late complications or pleural or bleeding/haemothorax occurred in the cohort of FNA procedures whereas in two cases who underwent CNB a minimum haemothorax occurred, without any further therapeutic management required. No late complications occurred. All the 62 patients did not refer significant pain during and after procedure (Numerical Rating Scale NRS ≤ 3).
Morphologic and molecular profiling of NSNs
Based on early disease stage, all the enrolled patients were addressed to surgical resection of lung cancer nodules to exclusive radiotherapy or to exclusive radiotherapy.
In 20 out of the 37 cases diagnosed through FNA, surgical resection was conducted at our Institution. The latter allowed the unique opportunity to perform a complete morphological and molecular match between the FNA-derived samples and their corresponding removed tissue. Surgical resection confirmed the cytological diagnosis of invasive or minimally invasive ADC in all the 20 cases. One case was in situ, 4 were minimally invasive and 15 invasive. The predominant histopathological pattern was lepidic in 7 (35%) cases, papillary in 6 (30%), acinar in 3 (15%), and solid in 1 (5%); 3 cases (15%) had an equivalent proportion of acinar and papillary, acinar and lepidic, and papillary and lepidic components. Seventeen cases showed the coexistence of more patterns: 4 acinar and lepidic, 1 each lepidic and papillary, papillary and acinar, solid and micropapillary, 3 lepidic acinar and papillary, 2 acinar papillary and micropapillary, two lepidic papillary and micropapillary, 2 lepidic, acinar, papillary and micropapillary. Three cases showed a homogeneous pattern, 1 acinar, 1 papillary and 1 lepidic. Overall, a lepidic component was present in 13 cases, acinar in 14, papillary in 12, micropapillary in 8, and solid in 1. No specific pattern could be recognized in FNA cytological samples but unequivocal papillae in the case with exclusive papillary architecture. The occurrence of unsatisfactory FNA samples was not associated with any specific histological pattern. No acinar components in non-solid nodules as acinar components could account for solid portion of the mixed subsolid-nodules.
PD-L1 immunostains could be evaluated in 30 cytological samples, while the remaining 7 did not reach the cellularity threshold for evaluation. TPS was < 1% in 26 cases, > 1%/< 50% in 3, and > 50% in 1. All surgical samples showed TPS < 1%. Of the 20 cases that could be evaluated on both cytologic and surgical samples, 18 were concordantly TPS 0, and 2 showed TPS > 1% < 50 on the biopsy samples.
EGFR mutations were identified in 2 of the 28 cases (7%) with adequate material (one exon 19 deletion and L858R); no case showed ALK/EML4 or ROS1 translocations.
Eight of the 25 cases diagnosed through CNB were patients that after the biopsy decided to continue the diagnostic-therapeutic path in other structures. In eleven of the 25 cases, surgical resection was performed. Surgical resection confirmed the cytological diagnosis of invasive or minimally invasive ADC in all 11 cases. The predominant histopathological pattern was acinar in 8 cases, papillary in 2 and acinar in 1.
PD-L1 expression could be evaluated in 22 samples, while the remaining three samples did not reach the cellularity threshold for evaluation. TPS was < 1% in 15 cases, > 1%/< 5% in 4 cases, > 5%/< 50% in 2 cases, > 50% in 1 case.
EGFR mutations were identified in 4 of the 25 cases (16%) with adequate material (one exon 19 deletion, L858R, L861Q, G719A); no case showed ALK/EML4 or ROS1 translocations.
Overall, being the population evaluated in the study homogenous, the Chi squared analysis (with degree of statistical freedom k = 1) of two distribution regarding the EGFR mutational profiling, allows us to reject the null hypothesis that the two groups FNA biopsy and CNB biopsy) are the same, whereas regarding the PD-L1 expression the two frequencies are coherent with the expected one. In other words, by comparing the two bioptic techniques, FNA and cell block cytology result in an EGFR mutational frequency lower than the expected one. In conclusion, cell-block cytology appears to be adequate for IHC stain but not in case of DNA direct sequencing.