Lung squamous cell carcinoma (SCC) has always been considered a monomorphic entity, different from lung adenocarcinoma which is known to be a very heterogeneous tumor from morphological and molecular point of view. Just two histological subtypes of SCC are recognised, the basaloid and lymphoepithelioma-like histotypes, as in other sites different from the lung. Recently, different studies tried to expand the classification of SCC by adding different subtypes based on morphological characteristics (such as keratinization or clear cell features) or different growth patterns (papillary or basaloid). We report a case of squamous cell carcinoma with a previously unreported, distinctive and predominant "lepidic" growth pattern, with its immunophenotypical and molecular characterization

A. Del Gobbo

A. Vingiani

E.  Bonaparte

E. Masci

G.  Faillace

S.  Barbaro

S.  Ferrero

AIR Universita degli studi di Milano

Int J Clin Exp Pathol 2016;9(7):7668-7673
www.ijcep.com /ISSN:1936-2625/IJCEP0029043
Case Report 
Pulmonary squamous cell carcinoma with lepidic 
growth pattern: new insights into lung cancer  
classification
Alessandro Del Gobbo1*, Andrea Vingiani1*, Emilia Masci2, Giuseppe Faillace2, Salvatore Barbaro2, Eleonora 
Bonaparte1, Stefano Ferrero1,3
1Division of Pathology, Fondazione IRCCS Ca’ Granda, Ospedale Maggiore Policlinico, via F. Sforza, 35, 20122 Mi-
lan, Italy; 2Division of General Surgery, Ospedale Bassini ICP, via Gorki 50, 20092 Cinisello Balsamo (Milan), Italy; 
3Department of Biomedical, Surgical and Dental Sciences, University of Milan Medical School, Milan, Italy, via F. 
Sforza, 35, 20122 Milan, Italy. *Equal contributors.
Received March 24, 2016; Accepted May 28, 2016; Epub July 1, 2016; Published July 15, 2016
Abstract: Lung squamous cell carcinoma (SCC) has always been considered a monomorphic entity, different from 
lung adenocarcinoma which is known to be a very heterogeneous tumor from morphological and molecular point of 
view. Just two histological subtypes of SCC are recognised, the basaloid and lymphoepithelioma-like histotypes, as 
in other sites different from the lung. Recently, different studies tried to expand the classification of SCC by adding 
different subtypes based on morphological characteristics (such as keratinization or clear cell features) or different 
growth patterns (papillary or basaloid). We report a case of squamous cell carcinoma with a previously unreported, 
distinctive and predominant “lepidic” growth pattern, with its immunophenotypical and molecular characterization. 
Keywords: Lung pathology, squamous cell carcinoma, lepidic growth pattern
Introduction
Squamous cell carcinoma (SCC) accounts for 
25-30% of all non-small cell lung cancers, often 
linked to a history of smoking [1]. During the 
past century, SCC was the most common sub-
type of NSCLC, but starting from ’70 s a de- 
crease of SCC prevalence relative to adenocar-
cinomas of the lung was noted and, today, ade-
nocarcinoma of the lung is the most common 
subtype of NSCLC [2]. Histologically, SCC is a 
malignant epithelial tumour composed of cells 
with large and abundant cytoplasm and irregu-
lar, hyperchromatic nuclei with small nucleoli 
showing some degrees of keratinisation, pearls 
formation and intercellular bridges [3]. 
Histological variants of SCC are not fully evalu-
ated and just two subtypes are recognised, the 
basaloid and lymphoepithelioma-like subtypes, 
as in other sites different from the lung [2].
According to the previous literature, only a 
minority of cases arises in small peripheral air-
ways [4], although some recent studies suggest 
a proportional increase of peripheral type carci-
noma. Funai et al [5] subdivided peripheral 
type squamous cell carcinoma according to the 
growth pattern into three types: the alveolar 
space-filling type, in which tumoral cell nests 
grow filling the alveolar space separated by thin 
preexisting septa; the expanding type, showing 
solid growth, destroying or compressing the 
surrounding parenchyma, and the combined 
type. 
The molecular landscape of SCCs appears to 
be characterized by different driver mutations 
respect to lung adenocarcinomas (ADCs). On- 
cogenic activation of PIK3CA, AKT1 and DDR2 
genes occur respectively in 9%, 7.1% and 3.8% 
of SCC, while EGFR, KRAS, MEK1, ERBB2 and 
ALK activating mutations are more frequently 
involved in ADCs [6, 7]. 
We report a case of squamous cell carcinoma 
with a previously unreported, distinctive pre-
dominant “lepidic” growth pattern.
Materials and methods
A 73-year-old male patient with an history of 
HCV-related hepatopathy, hypertension, subre-
nal abdominal aortic aneurysm, chronic ob- 
Lepidic pulmonary squamous cell carcinoma
7669 Int J Clin Exp Pathol 2016;9(7):7668-7673
structive pulmonary disease (COPD) due to 
tabagism and left radical nefrectomy for renal 
cell carcinoma came to our attention for dizzi-
ness and collapse.
A routine chest X-ray revealed a mass on the 
right lung, and high-resolution computed-to- 
mography (CT) scan of the chest and the abdo-
men confirmed a nodule measuring 2.5 cm in 
the middle right pulmonary lobe, another nod-
ule measuring 1.5 cm with speculated, irregu-
lar and infiltrative margins in the upper left pul-
monary lobe and the presence of right hilar and 
mediastinal lymphadenopathy (Figure 1).
The PET/CT scan indicated an intense 18F-FDG 
activity in the middle right lobe (Standard 
Uptake Value = 5) and in the upper left lobe 
(SUV = 3, 4). 
No other abnormal 18F-FDG uptake and no 
other localization of disease were identified at 
the clinical and imaging staging. The blood 
tumor markers were all within the normal rang-
es. Conventional bronchoscopy with flexible 
endoscope did not show pathological findings 
and bronchoalveolar lavage (BAL) was not 
diagnostic. 
Left pulmonary nodule was not candidated for 
CT-guided percutaneous biopsy because of dif-
ficult lesion accessibility without a safe window 
for needle entry. In consideration of the clinical 
and imaging findings, the patient was candi-
date for a surgical lung biopsy of the left pulmo-
nary solid nodule. Video-assisted thoracic sur-
gery (VATS) with wedge resection of the upper 
left lobe was performed. The surgical thoraco-
scopic procedure was performed with the use 
of three ports: the pulmonary wedge resection 
of the left lung apex was made by the use of an 
endo-GIA linear stapling device removing the 
nodule completely. No additional lymph node 
sampling was performed considering the pres-
ence of controlateral pulmonary disease. A 
PET/CT scan performed forty days after surgery 
detected no more metabolic activity in the mid-
dle right pulmonary lobe suggesting the resolu-
tion of a flogistic disease; therefore non addi-
tional surgery procedure and no adjuvant th- 
erapy for lung cancer was indicated by onco- 
logists.
Formalin-fixed, paraffin-embedded surgical 
specimens were stained with haematoxylin and 
eosin, and immunohistochemical stainings with 
antibodies directed against cytokeratin 7 (clone 
SP52), cytokeratin 20 (clone Ks20.8), cytokera-
tin 5-6 (clone D5/16 B4), p40 (clone BC28), 
TTF-1 (clone SP141) and Napsin A (clone 
MRQ40) were performed.
Immunohistochemistry was performed using 
the automatic system BenchMark XT (Ventana 
Medical Systems, Inc. Tucson, Arizona, USA). 
Reactions were revealed using the UltraViewTM 
Universal DAB, a biotin-free, multimer-based 
detection system, according to the manufac-
ture’s instruction.
Tumour genotyping by MassARRAY 
In order to characterize the molecular profile of 
the tumor, a panel of mutations, insertions and 
deletions of the genes most frequently involved 
in NSCL genetic alterations was investigated. 
The Catalogue of somatic mutations in cancer 
(COSMIC) database was consulted to select the 
hotspot regions to analyze. Tumor DNA was iso-
lated from formalin fixed paraffin embedded 
(FFPE) tissue sections, using the Biostic FFPE 
tissue DNA isolation Kit (Mo Bio Laboratories, 
Carlsbad, USA), following the manufacturer’s 
instructions. The MALDI-TOF (Matrix Assisted 
Laser Desorption Ionization Time-of-Flight) 
analysis was performed on 30 ng of DNA. 
MassARRAY Analyzer 4 was employed (Agena 
Bioscience, Hamburg, Germany), according to 
the iPLEX Pro application guide, using Complete 
iPLEX Pro Genotyping Reagent Set and 
SpectroCHIP II Arrays and Clean Resin Kit 
(Agena Bioscience, Hamburg, Germany). Mass- 
ARRAY Typer 4.0 software was used for data 
analysis. 
Figure 1. High-resolution computed-tomography (CT) 
scan of the chest and the abdomen showing a nod-
ule nodule measuring 1.5 cm in the upper left pul-
monary lobe.
Lepidic pulmonary squamous cell carcinoma
7670 Int J Clin Exp Pathol 2016;9(7):7668-7673
Results
Histopathological findings
Macroscopically, the nodule measured 1.3 cm 
and, on cut sections, it had a grayish appear-
ance, with ill-defined margins and a sub-pleural 
localization. All the nodule was sampled and 
paraffin-embedded for histological examina- 
tion.
Microscopical examination showed a moder-
ately differentiated (G2) squamous cell carci-
noma, exhibiting focal but clearly visible kerati-
Figure 2. Morphological features of the nodule. Low-power magnification showed a central, solid scar with periph-
eral lepidic growth pattern (A. 0.5x). At a higher magnification, lepidic growth pattern can be better appreciated, 
with squamous cell neoplastic population growing over the pre-existing alveolar septa, without destruction of the 
parenchyma (B, C. 5x; D-G. 10x). Cytological details of the neoplastic population morphologically indicate squamous 
differentiation (H. 20x).
Lepidic pulmonary squamous cell carcinoma
7671 Int J Clin Exp Pathol 2016;9(7):7668-7673
nization, characterized by an extensive lepidic 
growth: together with a central scar-like compo-
nent, with an infiltrative growth pattern in the 
centre of the lesion, some areas showed malig-
nant squamous cells growing along preexisting 
alveolar walls, preserving parenchymal archi-
tecture, frequently in multiple layers, displacing 
pneumocytes toward the central portions of 
alveolar lumen (Figure 2). 
Strong immunoreactivity for p40 (Figure 3A), 
p63 (Figure 3B) and cytokeratins 5-6 (Figure 
3C) confirmed the squamous nature of the 
lesion, while TTF-1 (Figure 3D) and Napsin A 
(Figure 3E) highlighted the intact frame of alve-
olar pneumocytes, with no staining in the neo-
plastic elements. Other immunohistochemical 
showed negativity in tumoral cells for cytokera-
tin 7 and 20.
Molecular findings
We genotyped the tumor investigating the most 
frequent driver mutations of NSCLC.
We did not find any mutations in PIK3CA, AKT1 
and DDR2, which are typical of SCCs, either in 
EGFR, KRAS, MEK1, ERBB2 and ALK, generally 
found in ADCs.
Discussion
If primary lung adenocarcinoma is known to be 
a very heterogeneous tumor in many aspects 
with different morphological subtypes and 
molecular mutations, on the contrary squa-
mous cell carcinoma has always been consid-
ered a “monomorphic”, solid entity [3].
Funai et al [5] tried to investigate different sub-
types also in SCC, identifying in peripheral 
tumors three different growth pattern, the alve-
olar space-filling type, the expanding type and 
the combined type. 
The alveolar space-filling type of SCC is charac-
terized by filling of the alveolar space without 
destroying alveolar septa and it has the most 
favorable clinical prognosis. The expanding 
Figure 3. Immunohisto-
chemical results. Stain-
ings for p40 (A), p63 
(B) and cytokeratins 
5-6 (C) highlighted the 
neoplastic population, 
while TTF1 (D) and Nap-
sin A (E) stained normal 
pneumocytes.
Lepidic pulmonary squamous cell carcinoma
7672 Int J Clin Exp Pathol 2016;9(7):7668-7673
type corresponds to the classic tumor nodule 
with infiltrative margins and with destruction of 
the pre-existing parenchyma and the combined 
type is a mixture of these two entitites.
Alveolar space-filling type can be considered a 
squamous evolution, a more advanced phase, 
of lepidic growth type, which is peculiar of ade-
nocarcinoma: in lepidic-growth adenocarcino-
ma, the neoplasm arises from cells lining the 
alveoli and spreads along their walls, but in 
alveolar space-filling type squamous cell carci-
onoma, the neoplastic elements are not limited 
to cover septa, but they fill entirely the alveolar 
spaces.
In addition, a recent work by Kadota et al [8] 
indicates for SCCs five different subtypes: kera-
tinizing, non-keratinizing, clear cell (which are 
not properly a growth pattern at all), basaloid 
and papillary type, but this is simpler and far 
from the complex classification of adenocar- 
cinoma.
In our case, in the majority of the tumor nodule 
we did not have a proper alveolar filling but just 
only a lepidic growth along alveolar walls and 
we can speculate that the presence of this pat-
tern can be explained with a squamous meta-
plastic change of the alveolar epithelium that 
has subsequently undergone cancerization and 
invasion.
Moreover, immunohistochemical of the lesion 
confirmed the squamous nature of the neo- 
plasia.
Despite its relatively monomorphic presenta-
tion, molecular alterations in squamous cell 
lung cancers have not been comprehensively 
studied, and no targeted therapies have been 
developed.
Significantly altered pathways includes NFE2L2 
and KEAP1 in 34%, squamous differentiation 
genes in 44%, PI3K pathway genes in 47%, and 
CDKN2A and RB1 in 72% of tumours [9].
In our opinion, the discovery of new subtypes 
within squamous cell carcinomas can have sig-
nificant clinical impact, since research of 
molecular mutations, in mixed forms, should be 
guided by the morphology and could lead to 
new therapeutic strategies in these patients. 
This is well known in adenocarcinoma, where 
tumor heterogeneity influences evaluation of 
prognostic biomarkers [10].
We investigated the molecular profile of the 
tumor in order to identify the typical driver 
mutation of SCCs, but no alterations were 
found.
To our knowledge this is the first reported, mor-
phologically and molecularly documented case 
of lung squamous cell carcinoma with this pe- 
culiar histological presentation, and its detec-
tion confirms the recent studies indicating that 
squamous cell carcinoma is an entity which 
may arise with different subtypes and histologi-
cal growth patterns.
To highlight this tumor heterogeneity, a further 
measure should be to do a high number of sam-
ples of the nodules. In our case, the relatively 
small size of the nodule has allowed a sample 
of the tumor in its entirety.
Disclosure of conflict of interest
None.
Address correspondence to: Dr. Alessandro Del 
Gobbo, Division of Pathology, Fondazione IRCCS 
Ca’ Granda, Ospedale Maggiore Policlinico, via F. 
Sforza, 35, 20122 Milan, Italy. Tel: +39-025-503-
8494; Fax: +39-025-503-2860; E-mail: alessandro.
delgobbo@policlinico.mi.it  
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Pulmonary squamous cell carcinoma with lepidic growth pattern : new insights into lung cancer classification

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Pulmonary squamous cell carcinoma with lepidic growth pattern : new insights into lung cancer classification

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