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Cosgun et al. Mini-invasive Surg 2019;3:32 I http://dx.doi.org/10.20517/2574-1225.2019.024 Page 7 of 9
[19]
Moon et al. claimed that mediastinal lymph node dissection may not be necessary for clinical stage N0
NSCLC presenting with a ≤ 3 cm GGO-predominant nodule. Segmentectomy can be a preferred technique
if there is almost no lymph node metastasis at stations 12 and 11. In patients with adenocarcinoma and
a micropapillary or solid component, lobectomy should be considered because of possible interlobar and
[22]
intralobar lymph node metastasis , which may not be identified before and during surgery. A histologic
component may be an important factor in patients with nodal upstaging of clinically N0 tumors . It
[4]
has been shown that micropapillary and solid tumor patterns significantly increase the risk of nodal
upstaging [23,24] . Our study demonstrated that the micropapillary pattern is related to a higher rate of lymph
node positivity. However, we were not able to identify solid predominance as a risk factor for lymph node
positivity.

Spread through air spaces (STAS) was defined as spread of lung cancer tumor cells into air spaces in
the lung parenchyma adjacent to the main tumor. Three morphologic patterns of STAS were identified:
(1) micropapillary structures, consisting of papillary structures without central fibrovascular cores that
occasionally form ring-like structures within air spaces; (2) solid nests or tumor islands, consisting of solid
collections of tumor cells filling air spaces; and (3) single cells consisting of scattered discohesive single
[25]
cells . Lymphovascular invasion and high-grade morphologic pattern were identified more frequently in
STAS-positive than STAS-negative tumors. Besides this, the risk of locoregional or distant recurrence was
significantly higher in patients with STAS-positive than STAS-negative tumors who underwent limited
resection. However, this association was not noted in the lobectomy group .
[26]
Another remarkable finding of this study was the number of dissected lymph nodes. The number of
positive and total number of dissected lymph nodes were higher in the RATS compared to the VATS
groups (P = 0.06, P < 0.05, respectively). These results were compatible with those of previous studies from
[27]
our department . We believed that RATS increases the capability of mediastinal dissection. On the other
hand, our group has been performing VATS lobectomy consistently for more than a decade; we do not see
this finding in VATS.

Limitation of our study are as follows: this study is performed in a single center with relatively small size
population. We could not analyze the patients with preoperatively diagnosed N2 disease. Relatively a small
number of patients underwent mediastinoscopy and/or or EBUS preoperatively in our series.

The number of positive lymph nodes and lymph node status were comparable between the T groups and
subgroups in adenocarcinomas. These results may be related with heterogenous types and subgroups of
adenocarcinoma. We demonstrated that lymphovascular invasion and micropapillary predominance
could be considered candidates for nodal upstaging. Since these features of tumors cannot be identified
preoperatively in most patients, we recommended performing systematic hilar and mediastinal lymph
node dissection for an adenocarcinoma of any size considering minimally-invasive surgery; we preferred
the robotic-assisted approach.

DECLARATIONS
Authors’ contributions
Conceived and designed the study, wrote and reviewed the manuscript: Cosgun T
Collected and tabulated data, participated in manuscript writing: Kaba E, Ayalp K
Participated in manuscript writing and review: Toker A

Availability of data and materials
Not applicable.