Prognostic Significance and Classification Value of Tumor Budding,Single Cell Invasion,and Spread Through Airspaces (STAS) in Lung Squamous Cell Carcinoma

Abstract

Objective

Lung squamous cell carcinomas (LSCC) currently lack a standardized histopathological grading system, unlike their adenocarcinoma counterparts. In this retrospective study, we examined the prognostic significance and classification value of tumor budding (TB), single-cell invasion, tumor budding nest size (TBNS) grading system, and spread through airspaces (STAS).

Methods

About 268 patients who underwent surgical resection for LSCC between November 2011 and December 2021 were evaluated. TB was assessed in hematoxylin and eosin-stained sections at ×200 magnification from the area showing the most prominent budding activity. A 3-tier TBNS grading system was established by combining the number of tumor buds and the size of tumor cell nests. STAS presence was also evaluated.

Results

Our analysis revealed significant associations between high TBNS scores and adverse pathological features, including higher tumor stage, pleural and lymphovascular invasion, increased stromal fibrosis, and lymph node metastasis. Furthermore, survival analysis demonstrated that high TB, single-cell invasion, elevated TBNS scores, and the presence of STAS were all linked to reduced overall and disease-free survival (P < .005).

Conclusion

These findings suggest that TB, TBNS, and STAS are valuable histopathological markers that may offer additional prognostic insight beyond traditional staging parameters. Incorporating a standardized assessment of these features into routine pathology reports could improve prognostic stratification and inform clinical decision-making in patients with LSCC.

Keywords

spread through airspaces (STAS)lung squamous cell carcinoma prognosis tumor budding tumor budding and nest size (TBNS) grading system

Introduction

Lung carcinomas are the most common types of cancer that lead to death in men and women.¹ In the current World Health Organization (WHO) classification of lung carcinomas, squamous cell carcinomas (SCC) are classified as keratinizing, nonkeratinizing, and basaloid subtypes; nevertheless, these have not been shown to have prognostic or other clinical significance.² The latest WHO classification provides a classification for lung adenocarcinomas based on histological subtypes that are important for prognosis. A universally accepted grading system for lung SCC is still not available. The prognosis of lung adenocarcinomas is largely guided by the predominant histological growth patterns, as recommended by the International Association for the Study of Lung Cancer (IASLC).² Additional prognostic factors, such as spread through airspaces (STAS), have also been recognized and are increasingly included in histopathological reports.³

In lung SCC, tumor size and lymph node status are staged according to the 8th edition of the American Joint Committee on Cancer (AJCC) staging system.⁴ However, given the heterogeneity in clinical outcomes, there is increasing interest in identifying additional histopathological features that could serve as prognostic indicators. Among these, tumor budding and tumor cell nest size have recently gained attention.⁵

Tumor budding is defined as the presence of isolated single tumor cells or small clusters composed of fewer than 4 tumor cells at the invasive tumor front.⁶ Initially described and validated in colorectal cancers through the International Tumor Budding Consensus Conference (ITBCC) in 2016.⁶ Tumor budding has since been studied as a prognostic marker in various malignancies, with several publications confirming its adverse prognostic impact.^7–9

In addition, studies on different solid organ tumors such as oral SCC,¹⁰ pancreatic adenocarcinoma,¹¹ gastric adenocarcinoma,¹² and cervical SCC^13,14 have shown that tumor budding is an important prognostic feature, indicating low survival rate and early disease recurrence.

Our aim in this study is to evaluate the presence of keratinization, degree of fibrosis, tumor budding and severity, tumor cell nests in the tumor that we can use for histological grading, and to compare these findings with other clinicopathological parameters such as diameter, age, tumor diameter, perineural and lymphovascular invasion, and lymph node involvement, presence of STAS.

Material and Methods

Patient Selection and Data Collection

In this study, a total of 283 patients who underwent surgical resection of lung tumors and were diagnosed with SCC between June 2011 and May 2020 were included. Fifteen patients with unavailable slides or clinical data were excluded, and finally, a total of 268 patients were evaluated. All available hematoxylin and eosin (H&E) stained slides were reviewed by 2 pathologists (NU and NAF) who were blinded to clinicopathological and clinical information, using an Olympus BX46 microscope (Olympus, Tokyo, Japan) with a standard 22-mm-diameter eyepiece.

The degree of fibrosis of the tumor stroma was assessed in the mild (<25% of the whole tumor area), moderate (25%-50%), and severe (>50%) groups.¹⁵ It was determined microscopically whether there is STAS (Figure 1D). The clinicopathological parameters were obtained from the archive and re-examined under a light microscope.

Figure 1.

Parameters and Examples of Their Levels in Histopathological Examination of Patients. (A) Low Tumor Budding (H&E, ×200). (B) High Tumor Budding (H&E, ×200). (C) Single Cell Invasion (Cells—Arrow, H&E, ×200). (D) Spread Through Airspaces (STAS) in AQ8 Patients With Squamous Cell Carcinoma (STAS—Arrow, H&E, ×200).

Tumor Budding and the Cell Nest Size

The tumor budding was defined as a single tumor cell or a group of ≤4 tumor cells present at the infiltrating edge of the malignant tumor and divided into 3 groups: without (1 point), low (1-14 budding, 2 points) (Figure 1A), and high (≥15 budding, 3 points) (Figure 1B). Tumor budding was assessed in 10 fields of 0.24 mm² each. 1-2 points were indicated as low activity, and 3 points as high budding activity. The highest bud counts were analyzed individually within a single field (0.24 mm²). All evaluations were performed using a field area of 0.24 mm² at ×400 magnification. The cell nest size was defined as a minimal size of invasive tumor cell nests and divided into 4 groups: large (>15 cells, 1 point), medium (5-15 cells, 2 points), small cell nests (2-4 cells, 3 points), and single cell invasion (4 points) (Figure 1C).

Tumor budding and cell nest size were evaluated for each patient, and the total score derived from these 2 parameters was used to assign a grade according to a 3-tiered system, herein referred to as the “tumor budding and nest size” (TBNS) grading system.^14,16 Then, the total scores were derived by adding tumor budding activity (1-3 points) and cell nest size (1-4 points) scores. This grading system was categorized as G1 (well differentiated, total score 2 or 3), G2 (moderately differentiated, total score 4 or 5), and G3 (poorly differentiated, total score 6 or 7).

For evaluation of tumor budding, all slides were reviewed independently by 2 experienced Pathologists (NÜ, NAF).

STAS

STAS in non-small cell lung cancer (NSCLC), introduced into the 2015 WHO classification, is defined as the spread of micropapillary cluster, solid nest, and/or single cancer cells into airspaces in the lung parenchyma beyond the edge of the primary tumor.¹⁷ A large number of independent studies have confirmed that STAS is a predictor of recurrence and poor survival in lung adenocarcinoma.^18–20

The International Association for the Study of Lung Cancer Staging stated that STAS should be included as a histological descriptor in the 9th Edition of the TNM classification of lung cancer.²⁰

The presence of STAS is an easier and more understandable definition for the subtypes of lung adenocarcinomas. However, in the literature, a small number of studies have studied STAS in lung SCC.^20–23

Statistical Analysis

Statistical analyses were performed using IBM SPSS Statistics, Version 22.0 (SPSS Inc., Chicago, USA). Correlation between groups for categorical variables was assessed using Chi-square (Pearson Chi-square) and Fisher's Exact Test. Clinicopathological prognostic variables were investigated using univariate and multivariate Cox regression analysis to estimate disease-free survival and overall survival. The Kaplan-Meier method was used for survival analysis and evaluated with the log-rank test. A P-value of < .05 was accepted as statistically significant.

Ethical Approval

This study was approved by the Clinical Research Ethics Committee of the Istanbul Yedikule Chest Disease and Thoracic Surgery Training and Research Hospital (2021-94).

Results

Clinicopathological Characteristics

The ages of the 268 patients included in the study ranged from 40 to 81 years, with an average age of 62.4 years. About 253 (94.4%) of the patients were male, and 15 (5.6%) were female. Tumor diameters were 1 to 12 cm, and the average diameter in resection materials was 4.6 cm. Histopathological evaluation of the tumors reported 10 (3.7%) basaloid SCC, 84 (31.3%) nonkeratinizing, and 174 (65%) keratinizing SCC. Pleural invasion was detected in 60 (22.4%) (PL1 n = 29 (48.3%), PL2 n = 7 (11.7%), PL3 n = 24 (40%)), lymphovascular invasion was detected in 156 (58.2%) patients, perineural invasion in 98 (36.6%) patients, and necrosis in 181 (67.5%) patients. High budding activity was observed in 149 patients (55.6%), while single cell invasion was observed in a total of 104 patients (38.8%). Lymph node involvement was detected in 124 (46.2%) patients, and STAS were detected in 186 (69.4%) patients. When evaluated according to the degree of fibrosis, mild fibrosis was detected in 25 (9.3%) patients, moderate fibrosis in 108 (40.3%) patients, and severe fibrosis in 135 (50.4%) patients. The other clinicopathological features of the patients are summarized in Table 1.

Table 1.

Correlation of Tumor Budding, Cell Nest Size, and TBNS System With Clinicopathological Parameters in Lung Squamous Cell Carcinoma.

	Tumor Budding			Single Cell Invasion			TBNS Grade
Parameters	Low n(%)	High	P	Negative n(%)	Positive	P	G1 n(%)	G2	G3	P
Sex			.903			.380				.851
Male	114(45)	139(55)		157(62.1)	96(37.9)		18(7.1)	108(42.7)	127(50.2)
Female	7(46.7)	8(53.3)		11(73.3)	4(26.7)		2(13.3)	9(60)	4(26.7)
Age			.221			.305				.170
≥62	63(42)	87(58)		90(60)	60(40)		15(10)	47(31.3)	88(58.7)
<62	56(47.5)	62(52.5)		78(66.1)	40(33.9)		9(7.6)	50(42.4)	59(50)
Diameter			.053			.034				.081
<4 cm	67(49.6)	68(50.4)		93(68.9)	42(31.1)		16(11.8)	53(39.3)	66(48.9)
≥4 cm	52(39.1)	81(60.9)		75(56.4)	58(43.6)		8(6)	44(33.1)	81(60.9)
Histological subtype			.017			.225				.014
Keratinizing	70(40.2)	104(59.8)		103(59.2)	71(40.8)		10(5.7)	60(34.5)	104(59.8)
Non-keratinizing	47(55.9)	37(44.1)		59(70.2)	25(29.8)		14(16.7)	34(40.5)	36(42.8)
Basaloid	2(20)	8(80)		6(60)	4(40)		0(0)	3(30)	7(70)
Lymphovascular Invasion			.001			.001				.001
Absent	70(62.5)	42(37.5)		89(79.5)	23(20.5)		14(12.5)	56(50)	42(37.5)
Present	49(31.4)	107(68.6)		79(50.6)	77(49.4)		10(6.4)	41(26.3)	105(67.3)
Necrosis			.001			.001				.001
Absent	54(62.1)	33(37.9)		67(77)	20(23)		16(18.4)	40(46)	31(35.6)
Present	65(35.9)	116(64.1)		101(55.8)	80(44.2)		8(4.4)	57(31.5)	116(64.1)
Fibrosis			.001			.001				.001
Mild	25(100)	0(0)		24(96)	1(4)		12(48)	13(52)	0(0)
Moderate	77(71.3)	31(28.7)		92(85.2)	16(14.8)		10(9.3)	68(63)	30(27.7)
Severe	17(12.6)	118(87.4)		52(38.5)	83(61.5)		2(1.5)	17(12.6)	116(85.9)
Perineural invasion			.005			.001				.031
Absent	86(50.6)	84(49.4)		119(70)	51(30)		18(10.6)	69(40.6)	83(48.8)
Present	33(33.7)	65(66.3)		49(50)	49(50)		6(6.1)	28(28.6)	64(65.3)
Pleural invasion			.001			.001				.001
Absent	105(50.5)	103(49.5)		143(68.5)	65(31.5)		24(11.6)	82(39.4)	102(49)
Present	14(23.3)	46(76.7)		25(41.7)	35(58.3)		0(0)	15(25)	45(75)
Lymph node metastasis			.005			.001				.024
Absent	75(52.1)	69(47.9)		43(29.9)	101(70.1)		16(11.1)	60(41.7)	68(47.2)
Present	44(35.5)	80(64.5)		63(50.8)	61(49.2)		8(6.5)	37(29.8)	79(63.7)
STAS			.001			.001				.001
Absent	65(24.3)	17(6.3)		80(29.9)	13(4.8)		18(6.7)	47(17.5)	17(6.3)
Present	54(20.1)	132(49.3)		88(32.8)	87(32.5)		6(2.2)	50(18.6)	130(48.5)
WHO grade			.008			.017				.028
II	75(50.7)	73(49.3)		100(67.6)	48(32.4)		12(8.1)	64(43.2)	72(48.7)
III	46(38.3)	74(61.7)		68(56.7)	52(43.3)		12(10)	33(27.5)	75(62.5)
Stage			.007			.017				0.095
1	44(57.1)	33(42.9)		56(72.7)	21(27.3)		10(13)	33(42.3)	34(44.2)
2	57(43.2)	75(56.8)		79(59.9)	53(40.1)		11(8.3)	49(37.1)	72(54.6)
3	20(33.9)	39(66.1)		27(45.8)	32(54.2)		3(5.1)	15(25.4)	41(69.5)
pT			.002			.022				.002
1	45(69.2)	20(30.8)		52(80)	13(20)		9(13.8)	35(53,9)	21(32.3)
2	41(36.6)	71(63.4)		66(58.9)	46(41.1)		10(8.9)	32(28.6)	70(62.5)
3	24(40)	36(60)		34(56.7)	26(43.3)		3(5)	23(38.3)	34(56.7)
4	11(35.5)	20(64.5)		16(51.6)	15(48.4)		2(6.4)	7(22.6)	22(71)

Chi-square tests. Multivariate analysis. Bold values indicate statistical significance at P < .05 (n = 268).

Italicized values indicate statistically significant results (P < 0.05).

Tumor Budding and TBNS

High tumor budding was detected in 107 (39.9%) patients with lymphovascular invasion, 116 patients with necrosis, 117 patients with severe fibrosis, 46 patients with pleural invasion, and 80 patients with lymph node metastasis. Single cell invasion was detected in 77 patients with lymphovascular invasion, 80 patients with necrosis, 83 patients with severe fibrosis, 35 patients with pleural invasion, and 61 patients with lymph node metastasis. Of the 149 patients with high tumor budding, 104 were single cell invasion. According to the TBNS system, as the score increased (G3), lymphovascular invasion (105, 67.3%), severe fibrosis (116, 85.9%), pleural invasion (45, 75%), and STAS (130, 48.5%) were observed at higher rates.

In the high-tumor-budding group, 104 patients (59.8%) were classified as keratinizing SCC, while 37 patients (44.1%) were identified as non-keratinizing SCC. According to the TBNS grading system, 104 patients (59.8%) within the G3 poorly differentiated category also corresponded to the keratinizing SCC subtype.

STAS

STAS were identified in 186 (69.4%) patients, among which high-grade tumor budding was observed in 132 (49.3%) patients. Single-cell invasion was detected in 87 (32.5%) patients. According to the TBNS system, STAS-positive 130 (48.5%) patients were classified as grade 3 (G3), while 50 (18.6%) were classified as grade 2 (G2). In 102 (54.8%) of the STAS-positive patients, the tumor diameter exceeded 4 cm. A total of 122 (65.6%) patients were histologically diagnosed as keratinizing type SCC. Pleural invasion was noted in 47 (25.3%) patients, and lymph node metastasis was present in 84 (45.2%) patients. The follow-up period for the 105 (56.4%) STAS-positive patients was less than 41 months. In addition, STAS-positive tumors were more frequently associated with advanced pathologic stages (P = .001).

Survival and Clinicopathological Analysis

When tumor budding and clinicopathological features were analyzed, the presence of high-grade tumor budding was significantly associated with poor overall survival (P = .005) (Figures 2 and 3), single-cell invasion (P = .001), presence of STAS (P = .001), high TBNS grade (P = .001), and pleural invasion (P = .001). Similarly, when disease-free survival was evaluated, high-grade tumor budding correlated with shorter disease-free survival (P = .001), single-cell invasion (P = .001), presence of STAS (P = .005), high TBNS grade (P = .001) (Figures 2 and 3), pleural invasion (P = .001), advanced pathological tumor stage (pT stage) (P = .001), and lymph node metastasis (P = .002). No significant association was found between other clinicopathological parameters and either overall survival or disease-free survival (Table 2).

Figure 2.

Association of the Lung SCC Tumor Budding and Cell Nest Size With Overall Survival (A, C) and Disease-Free Survival (B, D) in the Test Cohort.

Figure 3.

Association of Tumor Budding and Cell Nest Size (TBNS) Grading System and Spread Through Airspaces (STAS) in Lung SCC With Overall Survival (A, C) and Disease-Free Survival (B, D) in the Test Cohort.

Table 2.

Multivariate Analysis for Overall Survival and Disease-free Survival in Lung Squamous Cell Carcinoma.

	Overall Survival		Disease-free Survival
	Exitus n= 36		Relapse Patients n=83
Variables	n(%)	P	n(%)	P
Histological subtype		.352		.147
Keratinizing	26(72.2)		55(66.3)
Non-keratinizing	8(22.2)		24(28.9)
Basaloid	2(5.6)		4(4.8)
Pleural invasion		.001		.001
Absent	20(55.5)		59(71.1)
Present	16(44.4)		24(28.9)
Lymph node metastasis		.020		.002
Absent	13(36.1)		34(41)
Present	23(63.9)		49(59)
Tumor budding		.005		.001
Absent	1(2.8)		2(2.4)
Low	7(19.4)		20(24.1)
High	28(77.8)		61(73.5)
Tumor budding cell nest size		.001		.001
Large cell size	1(2.8)		3(3.6)
Intermediate nest size	2(5.6)		10(12.1)
Small cell size	4(11.1)		31(37.3)
Single-cell invasion	29(80.5)		39(47)
TBNS grade		.001		.001
G1	1(2.8)		3(3.6)
G2	6(16.7)		18(21.7)
G3	29(80.5)		62(74.7)
Single-cell invasion		.001		.001
Negative	5(13.9)		44(53)
Positive	31(86.1)		39(47)
STAS		.001		.005
Absent	3(8.3)		21(25.3)
Present	33(91.7)		62(74.7)
WHO grade		.270		.025
II	17(47.2)		39(47)
III	19(52.8)		44(53)
pT		.124		.001
1	3(8.3)		10(12.1)
2	18(50)		33(39.8)
3	11(30.6)		29(34.9)
4	4(11.1)		11(13.2)
Stage		.014		.001
1	3(8.3)		12(14.5)
2	24(66.7)		44(53)
3	9(25)		27(32.5)

Bold values indicate statistical significance at P < .05.

Italicized values indicate statistically significant results (P < 0.05).

Discussion

Lung cancer is the most common cancer group worldwide and is also the leading cause of cancer death (18.7% of total cancer deaths).¹ The most important reason for this is that the majority of patients are in advanced stages at the time of diagnosis (70%).² The majority of lung cancer types are NSCLC.² The most common tumor types within NSCLC are adenocarcinoma and SCC.² A grading system was established for adenocarcinomas in 2011 by the IASLC, American Thoracic Society (ATS), and European Respiratory Society (ERS) groups, which groups them according to the predominant histological pattern.²⁴

It is not completely clear whether similar histological parameters have prognostic significance in lung SCC. Therefore, in recent years, various histological features have been investigated to better predict the prognosis of lung SCC. Among these parameters, high tumor budding, single cell invasion, and presence of STAS have attracted attention as an indicator of aggressive behavior and poor prognosis in lung SCC.^25,26 Studies by Taira et al²⁷ and Masuda et al²⁸ have demonstrated that high-grade tumor budding is significantly associated with adverse prognostic features such as lymph node metastasis, pleural invasion, and advanced tumor stage. Similarly, Gürel et al²⁹ reported that tumor budding correlated with shorter disease-free and overall survival in SCC patients. In our study, consistent with the literature, high-grade tumor budding was significantly associated with single-cell invasion, higher TBNS grade, presence of STAS, pleural invasion, and poor survival outcomes.

STAS has also been evaluated as a poor prognostic indicator in lung tumors.^29,30 Kutlay et al³¹ and Lu S et al³² showed that STAS presence in pulmonary SCC was significantly correlated with lymph node metastasis and poor survival. Our findings align with these results, showing that STAS-positive tumors tended to have larger diameters, higher tumor budding, pleural invasion, lymph node metastasis, and shorter survival.

The presence of STAS was significantly associated with adverse pathological features, including larger tumor size (P = .005), higher tumor budding (P = .001), pleural invasion (P = .001), and lymph node metastasis (P = .001) (P < .05 for all comparisons). Patients with STAS-positive tumors demonstrated a shorter follow-up duration, suggesting a poorer overall survival compared to STAS-negative patients (P = .001). Furthermore, the frequent detection of STAS in patients with advanced pathological stage supports the hypothesis that STAS may contribute to more aggressive tumor behavior and could serve as a prognostic indicator in lung SCC. These findings emphasize the importance of evaluating both STAS and tumor budding in routine pathological assessment to better stratify patients’ prognoses and guide postoperative management strategies.

Kadota et al¹⁶ emphasized that tumor budding is associated with stromal activation, suggesting a more invasive phenotype in lung SCC. Additionally, studies by Uruga et al³³ and Eguchi et al³⁴ in lung adenocarcinomas highlighted the prognostic impact of STAS, suggesting that its evaluation could influence surgical decisions and postoperative management.

Taken together, these findings emphasize the importance of integrating both tumor budding and STAS evaluation into routine histopathological assessment to stratify patients more accurately according to their prognosis and to tailor more effective postoperative management strategies.

Conclusion

In conclusion, our study demonstrates that both high-grade tumor budding, single cell invasion and the presence of STAS are independently associated with adverse clinicopathological features and poor survival outcomes in lung SCC. These histopathological parameters can serve as valuable prognostic indicators, and their routine evaluation should be encouraged to optimize treatment planning and follow-up strategies.

Footnotes

ORCID iDs

Nurcan Unver

Neslİhan Akanıl Fener

Ethical Approval

This study was approved by the Clinical Research Ethics Committee of the Istanbul Yedikule Chest Disease and Thoracic Surgery Training and Research Hospital (2021-94).

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Declaration of Conflicting Interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

References

Bray

Laversanne

Sung

, et al. Global cancer statistics 2022: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin. 2024;74(3):229-263. doi:10.3322/caac.21834

WHO Classification of Tumours Editorial BoardThoracic Tumors. 5th edn, Vol 5. International Agency for Research on Cancer; 2021.

Warth

Muley

Kossakowski

, et al. Prognostic impact of intra-alveolar tumor spread in pulmonary adenocarcinoma. Am J Surg Pathol. 2015;39(6):793-801. doi:10.1097/PAS.0000000000000409

Amin

Greene

Edge

, et al. The Eighth Edition AJCC Cancer Staging Manual: continuing to build a bridge from a population-based to a more “personalized” approach to cancer staging. CA Cancer J Clin. 2017;67(2):93-99. doi:10.3322/caac.21388

Kadota

Nitadori

Woo

, et al. Comprehensive pathological analyses in lung squamous cell carcinoma: single cell invasion, nuclear diameter, and tumor budding are independent prognostic factors for worse outcomes. J Thorac Oncol. 2014;9(8):1126-1139. doi:10.1097/JTO.0000000000000253

Lugli

Kirsch

Ajioka

, et al. Recommendations for reporting tumor budding in colorectal cancer based on the International Tumor Budding Consensus Conference (ITBCC) 2016. Mod Pathol. 2017;30(9):1299-1311. doi:10.1038/modpathol.2017.46

Jass

Love

Northover

. A new prognostic classification of rectal cancer. Lancet. 1987;1(8545):1303–1306. doi: https://doi.org/10.1016/s0140-6736(87)90552-6.

Basile

Broudin

Emile

, et al. Tumor budding is an independent prognostic factor in stage III colon cancer patients: a post-hoc analysis of the IDEA-France phase III trial (PRODIGEGERCOR). Ann Oncol. 2022;33(6):628-637. doi:10.1016/j.annonc.2022.03.002

Ueno

Murphy

Jass

Mochizuki

Talbot

. Tumour ‘budding’ as an index to estimate the potential of aggressiveness in rectal cancer. Histopathology. 2002;40(2):127-132. doi:10.1046/j.1365-2559.2002.01324.x

10.

Badanale

Mohta

Wagh

, et al. Prognostic role of tumor budding and worst pattern of invasion in lymph node metastasis and disease-free survival in oral squamous cell cancer patients: result from Central India's Regional Cancer Centre. Indian J Otolaryngol Head Neck Surg. 2024 Aug;76(4):3261-3270. doi: 10.1007/s12070-024-04661-4. Epub 2024 Apr 12. PMID: 39130226; PMCID: PMC11306858.

11.

Lawlor

Veronese

Nottegar

, et al. Prognostic role of high-grade tumor budding in pancreatic ductal adenocarcinoma: a systematic review and meta-analysis with a focus on epithelial to mesenchymal transition. Cancers (Basel). 2019 Jan 19;11(1):113. doi: 10.3390/cancers11010113. PMID: 30669452; PMCID: PMC6356259.

12.

Pun

Luu

Swallow

, et al. Prognostic significance of tumour budding and desmoplastic reaction in intestinal-type gastric adenocarcinoma. Int J Surg Pathol. 2023 Sep;31(6):957-966. doi: 10.1177/10668969221105617. Epub 2022 Jun 20. PMID: 35726174; PMCID: PMC10492422.

13.

Zhang

Song

Shi

, et al. Further confirmation of a highly prognostic grading scheme based upon tumour budding and cell cluster size in cervical squamous cell carcinoma. Histopathology. 2025 May;86(6):967-978. doi: 10.1111/his.15404. Epub 2024 Dec 27. PMID: 39727044.

14.

Jesinghaus

Strehl

Boxberg

, et al. Introducing a novel highly prognostic grading scheme based on tumour budding and cell nest size for squamous cell carcinoma of the uterine cervix. J Pathol Clin Res. 2018;4(2):93-102. doi:10.1002/cjp2.95

15.

Weichert

Kossakowski

Harms

, et al. Proposal of a prognostically relevant grading scheme for pulmonary squamous cell carcinoma. Eur Respir J. 2016;47(3):938-946. doi:10.1183/13993003.00937-2015

16.

Kadota

Miyai

Katsuki

, et al. A grading system combining tumor budding and nuclear diameter predicts prognosis in resected lung squamous cell carcinoma. Am J Surg Pathol. 2017;41(6):750-760. doi:10.1097/PAS.0000000000000826

17.

Travis

Brambilla

Nicholson

, et al. The 2015 World Health Organization Classification of Lung Tumors: impact of genetic, clinical and radiologic advances since the 2004 classification. J Thorac Oncol. 2015;10(9):1243-1260. doi:10.1097/JTO.0000000000000630

18.

Kadota

Nitadori

Sima

, et al. Tumor spread through air spaces is an important pattern of invasion and impacts the frequency and location of recurrences after limited resection for small stage I lung adenocarcinomas. J Thorac Oncol. 2015;10(5):806-814. doi:10.1097/JTO.0000000000000486

19.

Kimura

Nakamura

Omura

, et al. Novel imprint cytological classification is correlated with tumor spread through air spaces in lung adenocarcinoma. Lung Cancer. 2020;148(10):62–68. doi:10.1016/j.lungcan.2020.08.005

20.

Travis

Eisele

Nishimura

, et al. The International Association for the Study of Lung Cancer (IASLC) staging project for lung cancer: recommendation to introduce spread through air spaces as a histologic descriptor in the ninth edition of the TNM Classification of Lung Cancer. Analysis of 4061 pathologic stage I NSCLC. J Thorac Oncol. 2024;19(7):1028-1051. doi:10.1016/j.jtho.2024.03.015

21.

Dagher

Sulaiman

Bayle-Bleuez

, et al. Spread through air spaces (STAS) is an independent prognostic factor in resected lung squamous cell carcinoma. Cancers (Basel). 2022;14(9):2281. Published 2022 May 3. doi:10.3390/cancers14092281

22.

Kadota

Kushida

Katsuki

, et al. Tumor spread through air spaces is an independent predictor of recurrence-free survival in patients with resected lung squamous cell carcinoma. Am J Surg Pathol. 2017;41(8):1077-1086. doi:10.1097/PAS.0000000000000872

23.

Tan

Kadota

, et al. Spread through air spaces (STAS) is an independent predictor of recurrence and lung cancer-specific death in squamous cell carcinoma. J Thorac Oncol. 2017;12(2):223-234. doi:10.1016/j.jtho.2016.09.129

24.

Travis

Brambilla

Noguchi

, et al. International association for the study of lung cancer/American Thoracic Society/European Respiratory Society International Multidisciplinary Classification of Lung Adenocarcinoma. J Thorac Oncol. 2011;6(2):244-285. doi:10.1097/JTO.0b013e318206a221

25.

Zombori-Tóth

Hegedűs

Almási

, et al. Proposal of a grading system for squamous cell carcinoma of the lung - the prognostic importance of tumour budding, single cell invasion, and nuclear diameter. Virchows Arch. 2023;483(3):393-404. doi:10.1007/s00428-023-03612-8

26.

Stögbauer

Lautizi

Kriegsmann

, et al. Tumour cell budding and spread through air spaces in squamous cell carcinoma of the lung - determination and validation of optimal prognostic cut-offs. Lung Cancer. 2022;169(7):1–12. doi:10.1016/j.lungcan.2022.04.012

27.

Taira

Ishii

Nagai

, et al. Characterization of the immunophenotype of the tumor budding and its prognostic implications in squamous cell carcinoma of the lung. Lung Cancer. 2012;76(3):423-430. doi:10.1016/j.lungcan.2011.11.010

28.

Masuda

Kijima

Imamura

, et al. Tumor budding is a significant indicator of a poor prognosis in lung squamous cell carcinoma patients. Mol Med Rep. 2012;6(5):937-943. doi:10.3892/mmr.2012.1048

29.

Gürel

Ulukuş

Karaçam

, et al. The prognostic value of morphologic findings for lung squamous cell carcinoma patients. Pathol Res Pract. 2016;212(1):1-9. doi:10.1016/j.prp.2015.10.006

30.

Nicotra

Melan

Pezzuto

, et al. Significance of spread through air spaces and vascular invasion in early-stage adenocarcinoma survival: a comprehensive clinicopathologic study of 427 patients for precision management. Am J Surg Pathol. 2024;48(5):605-614. doi:10.1097/PAS.0000000000002199

31.

Kutlay

Gülhan

SŞE

Acar

Aslan

Tanrıkulu

. Impact of spread through air spaces (STAS) and lymphovascular invasion (LVI) on prognosis in NSCLC: a comprehensive pathological evaluation. Updates Surg. 2025;77(4):1205–1213. doi:10.1007/s13304-025-02170-9

32.

Tan

Kadota

33.

Uruga

Fujii

Fujimori

Kohno

Kishi

. Semiquantitative assessment of tumor spread through air spaces (STAS) in early-stage lung adenocarcinomas. J Thorac Oncol. 2017;12(7):1046-1051. doi:10.1016/j.jtho.2017.03.019

34.

Eguchi

Kameda

, et al. Lobectomy is associated with better outcomes than sublobar resection in spread through air spaces (STAS)-positive T1 lung adenocarcinoma: a propensity score-matched analysis. J Thorac Oncol. 2019;14(1):87-98. doi:10.1016/j.jtho.2018.09.005