Keywords
pattern - invasion - worst - prognostic - tongue - lymph node
Introduction
Broders first introduced in 1920 histopathological grading of squamous cell carcinoma
(SCC) based on the proportion of differentiated cells to undifferentiated or anaplastic
cells within the entire tumor cell population and graded as highly/well, moderately,
poorly differentiated, and undifferentiated tumors.[1]
[2] The utility of tumor differentiation using Broders' histopathological malignancy
grading system in predicting the clinical course and outcome of oral tongue squamous
cell carcinoma (OTSCC) has been found to be limited and criticized because of its
poor prognostic value, and lack of reproducibility, underscoring the need for more
complex grading systems. Studies by Brandwein-Gensler et al,[3] Almangush A et al,[4] Anneroth et al,[5] Bryne et al,[6] and Martínez-Gimeno et al[7] came into being where multiparameter prognostic models and scoring systems that
include nuclear pleomorphism, mitotic index, lymphocytic response, tumor growth pattern,
tumor thickness, degree of keratinization, depth of invasion, and pattern of invasion
(POI) have been proposed[7]
[8]
[9]
[10] to predict the survival of patients with OTSCC and there was a general agreement
that the most useful prognostic information can be deduced from the invasive front
of the tumor, where the deepest and presumably most aggressive cells reside.[11]
SCC was encountered as the most common histological diagnosis in the malignant neoplasm
of tongue; we conducted a retrospective study on 80 patients with an aim to study
the prognostic significance of the POI and other clinicopathological parameters such
as survival, stage, recurrence, depth of invasion, perineural invasion, and lymph
node status in OTSCC.
Materials and Methods
Tissue Specimens
Paraffin-embedded sections of 80 patients with OTSCC collected between January 2015
and December2017 from the hospital archives were evaluated. Only exclusion criteria
used were any patients receiving preoperative chemo- or radiotherapy and recurrent
cases. All the sections were from the surgical resection specimen. Patients with history
of any prior treatment for OTSCC, residual or recurrent cases, and biopsy specimens
were excluded.
Histological Evaluation
All the hematoxylin and eosin-stained histopathological slides were concurrently reviewed
and evaluated independently by two qualified pathologists (the first observer LMK
and the second observer YR) using the same type of microscope without any prior knowledge
of each patient's clinical details. All the hematoxylin and eosin-stained histopathological
slides were concurrently reviewed and evaluated independently by two qualified pathologists
(the first observer and the second observer) using the same type of microscope without
any prior knowledge of each patient's clinical details. A set criterion was formulated
for the evaluation of the slides as follows:
-
All the sections of the tumor were evaluated microscopically by the two pathologists
(LMK and YR).
-
The maximum depth of infiltration was calculated microscopically under 40x and would
be taken for consideration
-
The POI was taken for consideration in the section of maximum depth of thickness at
its infiltrating edge following the criteria set by Brandwein-Gensler et al[3] (details mentioned in the next paragraph) under high power resolution (40X).
-
Extratumoral angiolymphatic invasion as mentioned in College of American Pathologist
(CAP) guidelines was not taken into consideration as worst POI (WPOI) 5 in this study.
When the opinions of the two evaluators differed selecting the sections or maximum
depth of invasion, consensus was reached by discussion.
Histologic Variables and Invasion Pattern Grading
Tumor differentiation was done using Broders' grading system. Variables like depth
of invasion, lymph node metastasis, perineural invasion, and POI were evaluated.
Depth of invasion was measured from the base of adjacent normal epithelium to the
deepest point of invasive tumor.
Tumor POI was examined at the host–tumor interface. Invasive tumor front scoring system
defined by Brandwein-Gensler et al[3] was used in our study comprising patterns I to V. Pattern I represents tumor invasion
in a broad pushing manner. Pattern II represents tumor invasion with broad pushing
“fingers,” or separate large tumor islands, with a stellate appearance. Pattern III
represents invasive islands of tumor >15 cells per island. Pattern IV represents invasive
tumor islands <15 cells per island, including single cell invasion and single-cell
filing pattern. Pattern V represents tumor satellites of any size at distance of 1 mm
or more from intervening normal tissue (not fibrosis) at the invasive tumor front.
Statistical Analysis
Frequency tables of demographic and clinicopathological parameters were established.
Kaplan–Meier plot was constructed to present cumulative survival outcomes and compared
using the log-rank test. A p-value of < 0.05 was considered to be statistically significant.
Results
The distribution of patients by demographic and clinicopathologic factors is shown
in [Table 1]. The mean follow-up period was 35 months (range: 1–60 months). Out of the 80 patients,
18 patients died of OTSCC because of recurrence, whereas 40 were alive at the end
of the follow-up period, while remaining 22 patients were lost to follow-up.
Table 1
Demographic and clinicopathological features of 80 patients with oral tongue squamous
cell carcinoma
|
Parameters
|
Number of patients
|
(%)
|
Parameters
|
Number of patients
|
(%)
|
|
Age
|
|
|
Perineural invasion
|
|
|
|
<40 years
|
14
|
17.5
|
Present
|
31
|
38.7
|
|
≥40 years
|
66
|
82.5
|
Absent
|
49
|
61.3
|
|
Gender
|
|
|
Lymph Node Metastasis
|
|
|
|
Male
|
57
|
71.3
|
Present
|
31
|
38.7
|
|
Female
|
23
|
28.3
|
Absent
|
49
|
61.3
|
|
M:F
|
2.5:1
|
|
|
|
|
|
Differentiations
|
|
|
Recurrence
|
|
|
|
WDSCC
|
68
|
85
|
Present
|
18
|
22.5
|
|
MDSCC
|
10
|
12.5
|
Absent
|
62
|
77.5
|
|
PDSCC
|
2
|
2.5
|
|
|
|
|
Status
|
|
|
Tumor Depth
|
|
|
|
Alive
|
40
|
50
|
≤5mm
|
22
|
27.5
|
|
Dead
|
18
|
22.5
|
>5–10mm
|
39
|
48.8
|
|
Lost to follow-up
|
22
|
27.5
|
>10mm
|
19
|
23.8
|
|
Stage
|
|
|
Pattern
|
|
|
|
Stage I
|
6
|
7.5
|
Pattern I
|
0
|
0
|
|
Stage II
|
27
|
33.8
|
Pattern II
|
11
|
13.8
|
|
Stage III
|
26
|
32.5
|
Pattern III
|
40
|
50.0
|
|
Stage IV
|
21
|
26.3
|
Pattern IV
|
26
|
32.5
|
|
|
|
Pattern V
|
3
|
3.8
|
Abbreviations: MDSCC, moderately differentiated squamous cell carcinoma; PDSCC, poorly
differentiated squamous cell carcinoma; WDSCC, worst differentiated squamous cell
carcinoma.
OTSCC was more common in patients age≥40 years (82.5%) in comparison to <40 years
(17.5%). It had male preponderance (71.3%) over female (28.7) with male to female
ratio of 2.5:1.
Tumor differentiation pattern assessed using Broders' system of grading showed that
85% of tumors were well differentiated, 12.5% tumors were moderately differentiated,
and 2.5% tumors were poorly differentiated.
Tumor depth of >5 to 10 mm was seen in 48.8% followed by ≤5 mm in 27.5% and >10 mm
in 23.8% of patients.
The different patterns were predominantly pattern III (50%) followed by pattern II
(32.5%), pattern IV (13.8%), and the least was pattern V (3.8%). The pattern I was
not seen in our study ([Fig. 1]).
Fig. 1 The different patterns of infiltration, hematoxylin and eosin, 20X.
Most patients were in stage II (33.8%) followed by stage III (32.5%) and stage IV
(26.3%). Least common was stage I (7.5%).
Perineural invasion and lymph node metastasis were seen in 38.7% each, while recurrence
occurred in 22.5% of patients.
Survival Outcomes
The overall survival of patients with OTSCC at 1 year, 3 years, and 5 years was 92.9,
58.5, and 50.5, respectively. Depth of invasion, perineural invasion, nodal metastasis,
and POI correlate well with the overall survival in patients with OTSCC; however,
no statistically significance (p < 0.05) was seen.
There was an inverse relationship between POI with tumor stage and recurrence; however,
it did not show strong statistical association ([Table 2]).
Table 2 Relationship between pattern of invasion (POI) on oral tongue squamous cell carcinoma
with stage and recurrence.
A strong statistically significant association was found between POI with perineural
infiltration (<0.013) and lymph node metastasis (<0.0001; [Table 3]).
Table 3 Relationship between pattern of invasion (POI) on oral tongue squamous cell carcinoma
with perineural invasion (PNI) and lymph node (LN) metastasis.
Discussion
The present study assessed the effectiveness of clinicopathological parameters in
predicting the mortality as well as the prognostic significance of the POI at the
host–tumor interface of patients with OTSCC.
In the present study, the overall survival of patients with OTSCC at 1 year, 3 years,
and 5 years was 92.9, 58.5, and 50.5, respectively. A reduced 5-year survival has
been reported by Spiro et al for patients with oral tongue cancer.[12]
[13] We did not find a statistically significant relationship among the depth of invasion,
lymph node metastasis, and perineural invasion with patient mortality. The depth of
invasion by microscopic method is best evaluated only after the patient has undergone
surgical treatment of the tumor and hence the usefulness in prognostication is limited.
Studies done in early stage OTSCC found depth of invasion to be an independent prognostic
factor. A preoperative determination of tumor depth through MRI and ultrasonography
has been suggested by several groups.[14]
[15] Possibly the small sample size and inclusion of both early (T1-T2) and late stage(T3-T4)
OTSCC in the present study would explain the reason why a statistical significance
was not found between depth of invasion, lymph node metastasis, and perineural invasion
with overall survival.
Majority of the cases in the present study were well-differentiated SCC (85%) and
no association of differentiation with the POI was found. This was also observed in
study done by Nadaf et al,[16] and concluded that five POIs could serve as an individual prognostic marker irrespective
of the histologic differentiation of tumor. Different POIs have been reported for
SCCs of different sites, for example, the skin, head and neck, as well as the cervix
uteri SCCs and gastric and endometrial adenocarcinomas,[17]
[18]
[19]
[20] and a high grade of tumor cell dissociation at the invasive front has been reported
to be of prognostic value in different types of carcinomas. Several studies in OTSCC
have previously confirmed the relationship of unfavorable WPOI with poor prognosis
in OTSCC.[11]
[21]
Bryne et al reported grading system for invasive front that was found to have prognostic
significance.[9] In a study by Heerema et al showed that the POI (one of the features of Bryne's
malignancy grading system) is an independent prognostic factor in low-stage OSCC.[22] Nadaf et al showed that five POIs (one component of invasive tumor front) could
serve as an individual prognostic marker irrespective of the histologic differentiation
of tumor.[16] In a study by Almangush et al, tumor budding, the depth of invasion (DOI), and WPOI
were evaluated and it was found that they are significant prognostic markers for early
stage (T1 and T2, N0 M0) carcinomas of tongue.[23]
In our study, it was observed that recurrence was most commonly seen in pattern III
followed by pattern IV and there was no recurrence in pattern II. Many cases from
pattern V were lost to follow-up. However, there was an inverse relationship between
POI with tumor stage and recurrence, but it did not show strong statistical association,
probably due to smaller sample size as well as many patients with highest POI were
lost to follow-up. Similarly, Monteiro et al reported that the pattern of spread in
oral cancers show little or no relation to the clinical stage at presentation.[24] However, in another study by Odell et al on 42 OTSCC, the prognostic significance
of the invasive front grading and the close correlation between POI and metastasis
as well as any recurrence of the disease were demonstrated.[25]
We found that LN metastasis and PNI strongly correlate with the worst POI and were
found to be statistically significant. PNI was most commonly seen in association with
66.7% of pattern V followed by 61.5% of pattern IV and 27.5% in pattern III, and 18%
of pattern II. Lymph node metastasis was seen in 100% cases of pattern V followed
by 61.5% of pattern IV and in 30% of pattern III, but no lymph node metastasis was
seen in pattern II. Several studies also support the association between POI and lymph
node metastasis.[25]
[26] However, we have not found any studies that show association between perineural
infiltration with the pattern of invasion. Hence, we feel the need of to test further
in other studies to substantiate this strong association found in our study.
Conclusion
In conclusion, as observed collectively from different studies mentioned above, it
is well known that the most aggressive cells of tumor reside at the invasive front
of tumor and show poorer prognosis in relation to worse pattern of invasion at the
invasive front of tumor. The present study concluded that POI IV and V are significantly
associated with number of lymph nodes metastasis and perineural infiltration, and
hence can be an independent histopathologic prognostic parameter in OTSCC.
