MCO Molecular and Clinical Oncology 2049-9450 2049-9469 D.A. Spandidos 10.3892/mco.2019.1951 MCO-0-0-1951 Articles Clinicopathological features of small-sized peripheral squamous cell lung cancer KosakaTakayuki ShimizuKimihiro NakazawaSeshiru IijimaMisaki OhtakiYoichi AzumaYoko ObayashiKai NagashimaToshiteru YajimaToshiki MogiAkira KuwanoHiroyuki ShirabeKen Department of General Surgical Science, Gunma University Graduate School of Medicine, Maebashi, Gunma 371-8511, Japan Correspondence to: Dr Kimihiro Shimizu, Department of General Surgical Science, Gunma University Graduate School of Medicine, 3-39-22 Showa-machi, Maebashi, Gunma 371-8511, Japan, E-mail: kmshimizu@gmail.com 01 2020 18 11 2019 12 1 69 74 22032019 20082019 Copyright © 2019, Spandidos Publications 2019

Recent advances in imaging technology have enhanced the detection rate of small-sized peripheral lung cancers. The present study aimed to identify the clinicopathological differences between patients with small-sized peripheral squamous cell carcinoma (SCC) and adenocarcinoma (ADC). Patients with lung cancer who underwent radical surgical resection at Gunma University Hospital between July 2007 and October 2012 were retrospectively analyzed. Patients who exhibited small-sized peripheral tumors (pathological size, ≤2 cm) located within the outer-third of the lung field on preoperative computed tomography were enrolled in the present study. A total of 26 patients were diagnosed with SCC and 214 with ADC. The results revealed that patients with SCC exhibited higher rates of pleural invasion, vascular invasion and lymphatic invasion compared with ADC patients. Additionally, the rate of postoperative recurrence was higher in patients with SCC compared with ADC patients. Patients with ADC were subsequently into two groups: Solid ADCs (sADC) and non-solid ADCs (nsADC), which included pure ground glass nodules and part-solid ADCs. The results revealed that the incidence of pleural invasion, vascular invasion and lymphatic invasion, and the rate of postoperative recurrence in patients with sADCs were similar to those with SCC, but were also significantly higher when compared with nsADC patients. The present study concluded that patients with SCC and sADC may not be suitable candidates for sublobar resection, despite exhibiting small tumors that are located in the peripheral lung.

 lung cancer small peripheral lung cancer squamous cell carcinoma sublobar resection Introduction

Recent advances in imaging technology have enhanced the detection rate of small-sized peripheral lung cancers. Prior studies that analyzed the relationship between tumor size and prognosis revealed a favorable prognosis for small-sized tumors, especially those ≤2 cm in diameter (1,2). Both randomized and non-randomized studies have revealed good outcomes for patients who underwent sublobar resection of these small-sized tumors (3,4).

Squamous cell carcinoma (SCC) used to be a representative histological type of centrally-located lung cancer, but recent studies have reported an increase in peripherally-located SCCs. The incidence of peripherally-located SCCs, which was 15–30% around 25 years ago (5,6), increased to nearly 50% of diagnosed or resected SCC cases (7). Previous reports have revealed a difference in clinicopathological features between central-type and peripheral-type SCCs (8,9). A retrospective study showed that peripheral-type SCC had lower pathological stage, less lymphatic and vessel involvement, and less lymph node metastasis, but no significant difference in overall survival compared with central-type SCC (8). However, the frequency of lymph node metastasis in peripheral-type SCC differs between reports (10–12), and current information is insufficient to define the malignant potential or prognosis of such small-sized peripheral SCCs.

Most previous studies defined peripheral tumors as tumors located in or more peripheral to the fourth branching bronchus (12,13). However, this definition is difficult to use in clinical practice, and several studies of sublobar resection have thus defined peripheral tumors as tumors located within the outer third of the lung field on preoperative computed tomography (3,4), which is an easier clinical definition. However, no study has reported on the use of this definition to compare the clinicopathological and prognostic features of peripheral SCC and peripheral adenocarcinoma (ADC).

We therefore investigated the malignant potential of small-sized peripheral SCC by retrospectively comparing its clinicopathological features with those of ADC in surgically resected cases, based on the definition of ‘peripheral’ as the outer third of the lung field on preoperative computed tomography.

 Patients and methods <sec> <title>Patients

We retrospectively analyzed lung cancer patients who underwent radical surgical resection at Gunma University Hospital (Maebashi, China) between July 2007 and October 2012. We included all patients with tumors located within the outer third of the lung field on preoperative computed tomography, which were ≤2 cm in pathological size. Because our study mainly focuses on pathological characteristics, we used more accurate pathological size in this study rather than clinical size like other reports (12,14). Because the aim of this study is to investigate the malignant potential of tumor itself, and not the prognostic value, we included all surgical procedures; i.e., lobectomy, segmentectomy, and wedge resection. Standard procedure was lobectomy but segmentectomy was mainly applied for tumor with predominant ground glass nodule (GGN) component and wedge resection was applied for the patients with poor performance status or pulmonary function.

Medical records for each patient were reviewed for the following clinical data: Age, sex, smoking history, disease history, procedure of operation, pathological tumor size, pleural invasion, vascular invasion, lymphatic invasion, recurrence. Because our study included cases of wedge resection with no lymph node dissection, we did not include the information of pathological lymph node metastasis. We focused our analysis on the malignant potential of the primary tumor.

The present study was approved by the Institutional Review Board of Gunma University Hospital (approval no. 2017-027). Written informed consent was obtained from all patients prior to enrolment.

 Statistical analysis

Associations between histological type and clinicopathological features were analyzed using χ2, Fisher's, or t-tests. A two-sided value of P<0.05 was considered statistically significant. All analyses were performed using SPSS 25 (IBM Co., Chicago, IL, USA).

 Results <sec> <title>Clinical characteristics

Twenty-six patients were diagnosed with SCC and 214 with ADC. The clinical characteristics of the patients are shown in Table I. Patients with SCC were significantly older than those with ADC (74 years vs. 65 years; P<0.01), and 80% of SCC patients were male and almost all were smokers, compared with only half of ADC patients being male and smokers, respectively. There was no significant difference in the prevalence of coexisting or previously treated other cancers (46% vs. 34%; P=0.19) or lung comorbidities (27% vs. 14%; P=0.07) between the two groups. Wedge resection was performed more frequently in SCC compared with ADC patients (31% vs. 13%, respectively), while segmentectomy was performed more frequently in ADC compared with SCC patients (25% vs. 12%, respectively).

 Pathological characteristics

The pathological characteristics of the patients are shown in Table II. SCC tumors tended to be larger than ADC tumors, but the difference was not significant (1.59±0.36 vs. 1.43±0.39 P=0.05). The incidences of pleural invasion (33% vs. 13%; P<0.01), vascular invasion (50% vs. 15%; P<0.01), and lymphatic invasion (50% vs. 19%; P<0.01) were significantly higher in the SCC compared with the ADC group.

 Postoperative recurrence

The median follow-up periods were 38.5 months for SCC patients and 58.0 months for ADC patients (Table III). The rate of postoperative recurrence was higher in SCC compared with ADC patients (23% vs. 10%; P=0.04). SCC tended to be associated with distant metastases whereas ADC was associated with locoregional metastases, though there was no significant difference in the pattern of recurrence (P=0.08).

 Comparison between SCC and two types of ADC

Because ADCs with GGN component are well known to be tumors with good prognosis, we divided ADCs into two groups; solid ADC (sADC) and non-solid ADC (nsADC) including pure GGN and part-solid GGN. There was no SCC with GGN feature. The incidences of pleural invasion, vascular invasion, and lymphatic invasion of SCC were similar with sADC but significantly higher compared with the nsADC group (Table IV). The rate of postoperative recurrence was similar with sADC but significantly higher compared with the nsADC group (Table V).

 Discussion

In this study, we retrospectively examined the clinicopathological features of small-sized peripheral SCC in relation to its malignant potential. The incidences of pleural invasion, vascular invasion, and lymphatic invasion were all significantly higher in SCC compared with ADC, and SCC patients had a significantly higher postoperative recurrence rate when compared with ADC patients. However, there was no difference when we compared between SCC and sADC.

Previous studies have shown various results regarding the malignancy of peripheral SCC. The studies which compared peripheral and central SCC revealed that growth pattern, morphology, and immunophenotype differ between peripheral and central SCC, although there was no difference in prognosis (8,9). The studies which compared SCC and ADC showed that small-sized peripheral SCC had a poorer prognosis than ADC (15,16). In this study, we analyzed the malignant potential limited to peripheral small-sized tumor according to CT definition. We analyzed only post-operative recurrence and our results showed that SCC patients had a higher postoperative recurrence rate compared with ADC patients. Because various previous studies including ours of small-sized peripheral SCC contained small sample size, further large-scale analysis is required for further conclusion.

The present study found significantly higher incidences of pleural invasion, vascular invasion, and lymphatic invasion in patients with SCC compared with ADC. Visceral pleural invasion has been reported as a factor associated with poor prognosis, and the presence of pleural invasion increased the T stage from T1 to T2 in a recent TNM classification (17–19). Several reports suggested a possible cancer cell pathway from a tumor with pleural invasion through the pleural cavity and subpleural lymphatics and from hilar lymph nodes into the mediastinal lymph nodes (17,20). Vascular invasion was identified as a poor-prognosis factor, even in stage IA non-small cell lung cancer, because of a higher rate of distant metastasis (21–23). Lymphatic invasion was also related to a poor prognosis in stage IA non-small cell lung cancer (24,25), and several studies found that lymphatic invasion was correlated with a higher rate of lymph node metastasis (26). The association between small-sized peripheral SCC and these malignant factors may contribute to its higher postoperative recurrence rate.

Several reports have shown a favorable prognosis for ADC with GGN component compared with solid ADC (27,28). Similarly, our results showed worse malignant potential of solid ADC compared with ADC with GGN component. The incidences of pleural invasion, vascular invasion, lymphatic invasion, and postoperative recurrence of the SCC were similar with solid ADC. Therefore, small peripheral tumors can be divided into two groups; solid tumor and non-solid tumor, in terms of malignant potential. Although wedge resection was lower in sADC group compared to SCC, the recurrence rate was almost same. This data may reflect the higher malignant potential of sADC, i.e., ADC with micropapillary pattern which is a well-known malignant factor (29,30).

Previous studies demonstrated that sublobar resection was a potentially valid surgical option for small-sized tumors (3,4), while the results of large-scale multi-institutional prospective randomized trials are awaited to confirm this (e.g., JCOG0802 and CALGB140503). Furthermore, ADCs with a high proportion of ground glass opacity are classified as minimally invasive or non-invasive ADC (ADC in situ) (31), and complete resection of such minimally invasive or non-invasive ADCs leads to an extremely favorable prognosis (32,33). ADC has thus been regarded as a good candidate for sublobar resection, and large-scale multi-institutional prospective randomized trials are currently exploring this issue (e.g., JCOG0804). In contrast, the present study showed that even small-sized SCCs and sADC in the peripheral lung had malignant potential such as higher incidence of pleural, vascular, and lymphatic invasion, suggesting that solid tumors may not be a good candidate for sublobar resection. Further prospective randomized trials are awaited.

The present study had several limitations. First, this study was conducted retrospectively in a single institute and the sample size was too small to obtain a definitive conclusion. Second, we included patients who underwent wedge resection. Although the proportion of wedge resection was higher in the SCC cohort, there was no difference in the rate of local recurrence. Third, we did not perform analysis regarding lymph node metastasis, because our study included cases of wedge resection and segmentectomy with no mediastinal lymph node dissection. Fourth, since our aim in this study was focused on SCC, we just divided ADC into the current two categories. There might be further clinicopathological difference between part-solid GGN and pure GGN (28).

In summary, pleural invasion, vascular invasion, and lymphatic invasion are more common in patients with SCC compared with ADC, while SCC is also associated with a higher postoperative recurrence rate. In addition, incidence of these factors in SCC are similar with sADC. SCC and sADC may not be candidates for sublobar resection even if they are small-sized and located in the peripheral lung.

 Acknowledgements

Not applicable.

 Funding

No funding was received.

 Availability of data and materials

All data and materials in the present study were anonymized. All data generated or analyzed during this study are included in this published article.

 Authors' contributions

TK and KiS conceived and designed the study. SN, MI, YO, YA, KO, TN, AM, HK, KeS and TY obtained the data. TK, KiS and SN analyzed and interpreted the data. TK, KiS, SN and YO drafted the manuscript. MI, YA, KO, TN, TY, AM, HK and KeS critically revised the manuscript. All authors have read and approved the manuscript.

 Ethics approval and consent to participate

The present study was approved by the Institutional Review Board of Gunma University Hospital (Maebashi, China) (approval no. 2017-027). Written informed consent was obtained from all patients prior to enrolment.

 Patient consent for publication

All patients consented for their data and/or images to be published at the time of their surgeries.

 Competing interests

The authors declare that they have no competing interests.

 References PortJLKentMSKorstRJLibbyDPasmantierMAltorkiNKTumor size predicts survival within stage IA non-small cell lung cancerChest12418281833200310.1378/chest.124.5.182814605056 OkadaMNishioWSakamotoTUchinoKYukiTNakagawaATsubotaNEffect of tumor size on prognosis in patients with non-small cell lung cancer: The role of segmentectomy as a type of lesser resectionJ Thorac Cardiovasc Surg1298793200510.1016/j.jtcvs.2004.04.03015632829 KoikeTKoikeTSatoSHashimotoTAokiTYoshiyaKYamatoYWatanabeTAkazawaKToyabeSILobectomy and limited resection in small-sized peripheral non-small cell lung cancerJ Thorac Dis832653274201610.21037/jtd.2016.11.10628066606 OkadaMKoikeTHigashiyamaMYamatoYKodamaKTsubotaNRadical sublobar resection for small-sized non-small cell lung cancer: A multicenter studyJ Thorac Cardiovasc Surg132769775200610.1016/j.jtcvs.2006.02.06317000286 HuhtiESaloheimoMSutinenSReiniläADoes the location of lung cancer affect its prognosis?Eur J Respir Dis6446046519836309544 TomashefskiJFJrConnorsAFJrRosenthalESHsiueILPeripheral vs. central squamous cell carcinoma of the lung. A comparison of clinical features, histopathology, and survivalArch Pathol Lab Med11446847419902334253 KrimskyWMuganlinskayaNSarkarSVulchiMPatelPRaoSHammerJEvansRQureshiMHarleyDThe changing anatomic position of squamous cell carcinoma of the lung-a new conundrumJ Community Hosp Intern Med Perspect633299201610.3402/jchimp.v6.3329927987285 FunaiKYokoseTIshiiGArakiKYoshidaJNishimuraMNagaiKNishiwakiYOchiaiAClinicopathologic characteristics of peripheral squamous cell carcinoma of the lungAm J Surg Pathol27978984200310.1097/00000478-200307000-0001312826890 HayashiTSanoHEgashiraRTabataKTanakaTNakayamaTKashimaYHoriTNunomuraSFukuokaJDifference of morphology and immunophenotype between central and peripheral squamous cell carcinomas of the lungBiomed Res Int2013157838201310.1155/2013/15783824069587 SakuraiHAsamuraHWatanabeSSuzukiKTsuchiyaRClinicopathologic features of peripheral squamous cell carcinoma of the lungAnn Thorac Surg78222227200410.1016/j.athoracsur.2004.01.02915223433 FukuiTKatayamaTItoLAbeTHatookaSMitsudomiTClinicopathological features of small-sized non-small cell lung cancer with mediastinal lymph node metastasisLung Cancer66309313200910.1016/j.lungcan.2009.03.00419344976 NagashimaTSakaoYMunMIshikawaYNakagawaKMasudaMOkumuraSA clinicopathological study of resected small-sized squamous cell carcinomas of the peripheral lung: Prognostic significance of serum carcinoembryonic antigen levelsAnn Thorac Cardiovasc Surg19351357201310.5761/atcs.oa.12.0184323237927 MaeshimaAMMaeshimaAAsamuraHMatsunoYHistologic prognostic factors for small-sized squamous cell carcinomas of the peripheral lungLung Cancer525358200610.1016/j.lungcan.2005.11.01016483689 KinoshitaTOhtsukaTHatoTGotoTKamiyamaITajimaAEmotoKHayashiYKohnoMPrognostic factors based on clinicopathological data among the patients with resected peripheral squamous cell carcinomas of the lungJ Thorac Oncol917791787201410.1097/JTO.000000000000033825226427 TaoHHayashiTSanoFTakahagiATanakaTMatsudaEOkabeKPrognostic impact of lymphovascular invasion compared with that of visceral pleural invasion in patients with pN0 non-small-cell lung cancer and a tumor diameter of 2 cm or smallerJ Surg Res185250254201310.1016/j.jss.2013.05.10423830361 InoueMMinamiMShionoHSawabataNIdeguchiKOkumuraMClinicopathologic study of resected, peripheral, small-sized, non-small cell lung cancer tumors of 2 cm or less in diameter: Pleural invasion and increase of serum carcinoembryonic antigen level as predictors of nodal involvementJ Thorac Cardiovasc Surg131988993200610.1016/j.jtcvs.2005.12.03516678580 ShimizuKYoshidaJNagaiKNishimuraMIshiiGMorishitaYNishiwakiYVisceral pleural invasion is an invasive and aggressive indicator of non-small cell lung cancerJ Thorac Cardiovasc Surg130160165200510.1016/j.jtcvs.2004.11.02115999057 YoshidaJNagaiKAsamuraHGoyaTKoshiishiYSoharaYEguchiKMoriMNakanishiYTsuchiyaRVisceral pleura invasion impact on non-small cell lung cancer patient survival: Its implications for the forthcoming TNM staging based on a large-scale nation-wide databaseJ Thorac Oncol4959963200910.1097/JTO.0b013e3181a85d5e19458555 KawaseAYoshidaJMiyaokaEAsamuraHFujiiYNakanishiYEguchiKMoriMSawabataNOkumuraMVisceral pleural invasion classification in non-small-cell lung cancer in the 7th edition of the tumor, node, metastasis classification for lung cancer: Validation analysis based on a large-scale nationwide databaseJ Thorac Oncol8606611201310.1097/JTO.0b013e31828632b823478542 Manac'hDRiquetMMedioniJLe Pimpec-BarthesFDujonADanelCVisceral pleura invasion by non-small cell lung cancer: An underrated bad prognostic factorAnn Thorac Surg7110881093200110.1016/S0003-4975(00)02649-711308141 TsuchiyaTAkamineSMuraokaMKamoharaRTsujiKUrabeSHondaSYamasakiNStage IA non-small cell lung cancer: Vessel invasion is a poor prognostic factor and a new target of adjuvant chemotherapyLung Cancer56341348200710.1016/j.lungcan.2007.01.01917350137 ShojiFHaroAYoshidaTItoKMorodomiYYanoTMaeharaYPrognostic significance of intratumoral blood vessel invasion in pathologic stage IA non-small cell lung cancerAnn Thorac Surg89864869201010.1016/j.athoracsur.2009.09.04720172144 ShimadaYSajiHYoshidaKKakihanaMHondaHNomuraMUsudaJKajiwaraNOhiraTIkedaNPathological vascular invasion and tumor differentiation predict cancer recurrence in stage IA non-small-cell lung cancer after complete surgical resectionJ Thorac Oncol712631270201210.1097/JTO.0b013e31825cca6e22673056 HaradaMHatoTHorioHIntratumoral lymphatic vessel involvement is an invasive indicator of completely resected pathologic stage I non-small cell lung cancerJ Thorac Oncol64854201110.1097/JTO.0b013e3181f8a1f121079523 FunaiKSugimuraHMoritaTShundoYShimizuKShiiyaNLymphatic vessel invasion is a significant prognostic indicator in stage IA lung adenocarcinomaAnn Surg Oncol1829682972201110.1245/s10434-011-1729-921512862 KangDYLeeSLymphatic vessel invasion and lymph node metastasis in patients with clinical stage I non-small cell lung cancerThorac Cardiovasc Surg62521524201410.1055/s-0034-138478824905019 AsamuraHHishidaTSuzukiKKoikeTNakamuraKKusumotoMNagaiKTadaHMitsudomiTTsuboiMRadiographically determined noninvasive adenocarcinoma of the lung: Survival outcomes of Japan Clinical Oncology Group 0201J Thorac Cardiovasc Surg1462430201310.1016/j.jtcvs.2012.12.04723398645 SuzukiKKusumotoMWatanabeSTsuchiyaRAsamuraHRadiologic classification of small adenocarcinoma of the lung: Radiologic-pathologic correlation and its prognostic impactAnn Thorac Surg81413419200610.1016/j.athoracsur.2005.07.05816427823 MiyoshiTSatohYOkumuraSNakagawaKShirakusaTTsuchiyaEIshikawaYEarly-stage lung adenocarcinomas with a micropapillary pattern, a distinct pathologic marker for a significantly poor prognosisAm J Surg Pathol27101109200310.1097/00000478-200301000-0001112502932 KamiyaKHayashiYDouguchiJHashiguchiAYamadaTIzumiYWatanabeMKawamuraMHorinouchiHShimadaNHistopathological features and prognostic significance of the micropapillary pattern in lung adenocarcinomaMod Pathol219921001200810.1038/modpathol.2008.7918516041 TravisWDBrambillaENicholsonAGYatabeYAustinJHMBeasleyMBChirieacLRDacicSDuhigEFliederDBThe 2015 world health organization classification of lung tumors: Impact of genetic, clinical and radiologic advances since the 2004 classificationJ Thorac Oncol1012431260201510.1097/JTO.000000000000063026291008 YoshidaJNagaiKYokoseTNishimuraMKakinumaROhmatsuHNishiwakiYLimited resection trial for pulmonary ground-glass opacity nodules: Fifty-case experienceJ Thorac Cardiovasc Surg129991996200510.1016/j.jtcvs.2004.07.03815867771 MaeshimaAMTochigiNYoshidaAAsamuraHTsutaKTsudaHHistological scoring for small lung adenocarcinomas 2 cm or less in diameter: A reliable prognostic indicatorJ Thorac Oncol5333339201010.1097/JTO.0b013e3181c8cb9520125041

Clinical characteristics of patients with SCC and ADC.

Variables SCC (n=26) ADC (n=214) P-value
Median age, years (range) 74 (59–82) 65 (33–87) <0.01
Sex
  Male 21 (81%) 108 (50%) <0.01
  Female 5 (19%) 106 (50%)
Smoking history
  Never 1 (4%) 99 (46%) <0.01
  Current or former 25 (96%) 114 (54%)
Lung comorbidity
  Absent 19 (73%) 185 (86%) 0.07
  Present 7 (27%) 29 (14%)
    COPD 3 25
    IP 3 3
    CPFE 1 1
Coexisting or previously treated other cancer
  Absent 14 (54%) 142 (66%) 0.19
  Present 12 (46%) 72 (34%)
Surgical procedure
  Lobectomy 15 (58%) 133 (62%) 0.05
  Segmentectomy 3 (12%) 53 (25%)
  Wedge resection 8 (31%) 28 (13%)

SCC, squamous cell carcinoma; ADC, adenocarcinoma; COPD, chronic obstructive pulmonary disease; IP, interstitial; CPFE, combined pulmonary fibrosis and emphysema.

Pathological characteristics of patients with SCC and all ADC.

Variables SCC (n=26) ADC (n=214) P-value
Mean tumor size ± SD (mm) 1.59±0.36 1.43±0.39 0.05
Pleural invasion
  Negative 16 (67%) 185 (87%) <0.01
  Positive 8 (33%) 27 (13%)
Vascular invasion
  Negative 12 (50%) 179 (85%) <0.01
  Positive 12 (50%) 32 (15%)
Lymphatic invasion
  Negative 12 (50%) 171 (81%) <0.01
  Positive 12 (50%) 40 (19%)

SCC, squamous cell carcinoma; ADC, adenocarcinoma; SD, standard deviation.

Postoperative recurrence and survival rates of patients with SCC and all ADC.

Variables SCC (n=26) ADC (n=214) P-value
Median follow-up period (months) 38.5 58.0
Recurrence
  Absent 20 (77%) 193 (90%) 0.04
  Present 6 (23%) 21 (10%)
Pattern of recurrence
  Locoregional 2 15 0.08
  Distant 3 3
  Both simultaneously 1 3

SCC, squamous cell carcinoma; ADC, adenocarcinoma.

Pathological characteristics of patients with SCC and two groups of patients with ADC.

Variables SCC (n=26) (%) sADC (n=61) (%) nsADC (n=153) (%) P-value† P-value‡
Pleural invasion
  Negative 16 (67) 42 (69) 143 (95) <0.01 <0.01
  Positive 8 (33) 19 (31) 8 (5)
Vascular invasion
  Negative 12 (50) 35 (58) 144 (95) <0.01 <0.01
  Positive 12 (50) 25 (42) 7 (5)
Lymphatic invasion
  Negative 12 (50) 34 (57) 137 (91) <0.01 <0.01
  Positive 12 (50) 26 (43) 14 (9)

†P-value comparing the SCC group with the nsADC group; ‡P-value comparing the sADC group with the nsADC group. SCC, squamous cell carcinoma; sADC, solid adenocarcinoma; nsADC, non-solid adenocarcinoma.

Postoperative recurrence and survival rates of patients with SCC and two groups of patients with ADC.

Variables SCC (n=26) sADC (n=61) nsADC (n=153) P-value† P-value‡
Median follow-up period (months) 38.5 56.2 59.6
Surgical procedure
  Lobectomy 15 (58%) 46 (75%) 87 (57%) 0.06 0.06
  Segmentectomy 3 (12%) 9 (15%) 44 (29%)
  Wedge resection 8 (31%) 6 (10%) 22 (14%)
Recurrence
  Absent 20 (77%) 47 (77%) 146 (95%) <0.01 <0.01
  Present 6 (23%) 14 (23%) 7 (5%)
Pattern of recurrence
  Locoregional 2 10 5 0.47 1.00
  Distant 3 2 1
  Both simultaneously 1 2 1

†P-value comparing the SCC group with the nsADC group; ‡P-value comparing the sADC group with the nsADC group. SCC, squamous cell carcinoma; sADC, solid adenocarcinoma; nsADC, non-solid adenocarcinoma.