Keywords histopathology - immunohistochemistry - lymphoepithelial - salivary glands - sialadenitis
Introduction
Salivary glands give rise to more than 30 histologically distinct benign and malignant
tumors, constituting less than 2% of all tumors in humans and 3% of all head and neck
tumors. The most common site is the parotid gland comprising 80% of cases, and approximately
80% are benign and 20% are malignant. Among them are lymphoepithelial lesions (LELs),
rare lesions of the salivary glands, characterized by lymphocytic infiltration associated
with an epithelial proliferation.[1 ] LELs of salivary gland encompass a heterogeneous group of diseases that include
benign reactive lesions and malignant neoplasms. These pathologic entities sometimes
pose as diagnostic dilemmas.
Aim and Objective
The study was undertaken to highlight the importance of meticulous cytopathological
and histopathological examination (HPE) in solving the diagnostic challenges encountered
in the analysis of these salivary gland lesions.
Materials and Methods
A retrospective analysis of salivary gland lesions was undertaken over a period of
5 years from 2014 to 2019 in the department of pathology at our institute following
all the guidelines of the institutional ethics committee.
Inclusion Criteria
Salivary gland pathologies diagnosed either as chronic sialadenitis or reactive/benign/malignant
LELs on cytopathological examination were included in this study.
Salivary gland lesions diagnosed as poorly differentiated malignancy/carcinoma/metastatic
carcinoma on cytopathological examination, which turned out to be lymphoepithelial
carcinoma (LEC) on HPE.
Exclusion Criteria
Other salivary gland pathologies.
Details of age, gender, and other relevant clinical information were collected from
the medical records. May-Grunwald Giemsa stained fine-needle aspiration cytology (FNAC)
slides and corresponding Hematoxylin and Eosin stained slides sectioned from formalin
fixed paraffin embedded tissues and immunohistochemistry (IHC) slides were retrieved
from the archives in the department of pathology and evaluated.
Results
A total of 86 cases of salivary gland lesions diagnosed as mentioned above on FNAC
fulfilled the inclusion and exclusion criteria. Males slightly outnumbered females,
ratio being 1.4:1. Age range was very wide, from 1 to 95 years. Out of the 86 cases,
16 were subjected to HPE. Biopsy was not necessary in most of the cases diagnosed
as chronic sialadenitis. The submandibular gland was the predominant site of involvement
with 58 of these cases (67.44%), followed by 23 cases of the parotid (26.74%); three
cases involved both the parotid and the submandibular gland (3.49%), while the minor
salivary glands were implicated in two cases (2.33%; [Table 1 ]). The diagnoses encountered were chronic sialadenitis in 72 cases (83.7%), granulomatous
inflammation in 03 cases (3.5%), benign lymphoepithelial lesion (BLEL) in 03 cases
(3.5%), reactive inflammatory lesion in 02 cases (2.3%), and malignant entities in
06 cases (7%), thus benign entities totaling 80 and malignant 6. Chronic sialadenitis
predominantly affected the submandibular gland, while the other benign/reactive lesions
involved the parotid more. Both the major and the minor salivary glands were affected
by the malignant entities. Correlation of the cytopathologic diagnosis with HPE is
shown in [Table 2 ]. Out of the five cases of chronic sialadenitis diagnosed as such on FNAC for which
biopsy was done, 60% correlation was observed with the HPE diagnosis, that is, three
cases, while the remaining two cases turned out to be benign salivary gland neoplasms
on HPE, namely Warthin tumor and myoepithelioma. There was no discrepancy in the diagnosis
of BLEL/lymphoepithelial sialadenitis between FNAC and HPE ([Fig. 1 ]), whereas a lymphoepithelial cyst in the parotid had been rendered a cytopathologic
diagnosis of reactive inflammatory lesion.
Table 1
Diagnosis vis-à-vis site
Sr. No.
Diagnosis
Parotid (P)
Submandibular (SM)
Minor salivary glands
Both P + M
Abbreviations: BLEL, benign lymphoepithelial lesion; LES, lymphoepithelial sialadenitis.
1.
Chronic sialadenitis
15
55
01
01
2.
Granulomatous
02
01
0
0
3.
BLEL/LES
02
0
0
01
4.
Reactive inflammation
02
0
0
0
5.
Malignant
02
02
01
01
6.
Total
23
58
02
03
Table 2
Correlation of cytopathologic diagnosis with HPE
Sl. no.
Diagnosis (FNAC)
No. of cases
HPE done for
Cor-related with HPE
Percentage (%)
Not correlated with HPE
Percentage (%)
Abbreviations: BLEL, benign lymphoepithelial lesion; HPE, histopathological examination;
LES, lymphoepithelial sialadenitis.
1.
Chronic sialadenitis
72
05
03
60
02
40
2.
Granulomatous
03
–
–
–
–
–
3.
BLEL/LES
03
03
03
100
–
–
4.
Reactive
02
02
01
50
01
50
5.
Malignant
06
06
05
83.3
01
16.7
6.
Total
86
16
12
75
04
25
Fig. 1 (A ) Photomicrograph depicting the fine-needle aspiration cytology of benign lymphoepithelial
lesion showing polymorphous lymphoid infiltration along with scattered acini; May-Grunwald
Giemsa 200×, inset 400×. (B ) Corresponding tissue section showing benign lymphocytic infiltrate of salivary gland
with parenchymal atrophy and lymphoepitheliotropism; Hematoxylin and Eosin 40×, inset
200×.
FNAC proved to be a competent tool for the malignant LELs, as none of them were missed
([Table 3 ]). However, LEC, the histopathologic diagnosis in these cases, was mostly not categorically
stated on cytopathologic analysis. FNAC claimed these cases to be one of poorly differentiated
malignancy/poorly differentiated carcinoma/metastatic carcinoma, composed of sheets
of large polygonal to round cells having high nucleocytoplasmic ratio, round to oval
nuclei, coarse chromatin, prominent nucleoli, and scant cytoplasm ([Fig. 2 ]); the HPE divulged a tumor exhibiting total replacement and destruction of salivary
gland architecture by lymphoid cells along with presence of LELs and aggregates of
poorly differentiated large polygonal epithelial cells with round to oval vesicular
nuclei, prominent nucleoli, and scant cytoplasm ([Fig. 3 ]). Nevertheless, a lone discordance between a benign and a malignant diagnosis was
noted, which is discussed herewith. A 59-year-old female presented with a right postauricular
swelling (parotid), the initial FNAC report of which was inconclusive. Subsequently
excision biopsy was done that misinterpreted it as LEC. IHC for pancytokeratin (PanCK;
Dako) and leucocyte common antigen (LCA; Dako) were deemed to be positive in the atypical
epithelial cells and the lymphoid cells, respectively. However, a review report was
asked for on the same biopsy, which concluded lymphoepithelial sialadenitis with accompanying
fibrosis as the final and consensus diagnosis, with the IHC being revised as PanCK
positive in the remnant benign ductal cells, and LCA positive in the lymphoid cells
([Fig. 4 ]). The histiocytic population had been mistaken as poorly differentiated epithelial
cells of LEC, destruction of the glandular and acinar architecture, and the accompanying
infiltrating lymphoid cells further adding to the diagnostic confusion. The same patient
again presented 2 years later with right submandibular swelling. FNAC was done, which
revealed a possibility of LEC ([Fig. 5 ]). The lesion was surgically excised. HPE, however, favored granulomatous lymphoepithelial
sialadenitis with fibrosis ([Fig. 6 ]). Tuberculosis as a primary etiology was ruled out though. As regards the association
of LEC with Epstein–Barr virus (EBV), two cases showed positivity for EBV-latent membrane
protein 1 (EBV-LMP1) IHC (BioGenex), while the other three cases were negative, thus
accounting to an unlikely low proportion of positive cases (40%).
Table 3
Correlation of malignant LELs on FNAC with HPE
Sl. no.
Site
Diagnosis on FNAC
Diagnosis on HPE
Abbreviations: FNAC, fine-needle aspiration cytology; HPE, histopathological examination;
LEC, lymphoepithelial carcinoma; LELs, lymphoepithelial lesions; PDC, poorly differentiated
carcinoma.
1.
Submandibular gland
Poorly differentiated malignancy
LEC
2.
Submandibular gland
Poorly differentiated malignancy
LEC
3.
Parotid gland
Poorly differentiated carcinoma
LEC
4.
Minor salivary glands
Metastatic PDC/LEC
LEC
5.
Parotid gland
Metastatic PDC/LEC/PDC
LEC
6.
Parotid and submandibular glands
LEC
Granulomatous lymphoepithelial sialadenitis
Fig. 2 Photomicrograph showing the fine-needle aspiration cytology for a case of lymphoepithelial
carcinoma of the submandibular gland diagnosed on cytopathology as poorly differentiated
malignancy (May-Grunwald Giemsa 200×, inset 400×).
Fig. 3 (A ) Photomicrograph exhibiting the corresponding tissue section of the case of lymphoepithelial
carcinoma shown in Fig. 2, with (B ) the presence of lymphoepithelial lesion and (inset) aggregates of poorly differentiated
large polygonal epithelial cells ([A] 100×, [B] 200×, inset 400×; Hematoxylin and Eosin).
Fig. 4 Photomicrograph demonstrating the histopathological examination of lymphoepithelial
sialadenitis of the parotid misinterpreted previously as lymphoepithelial carcinoma
(Hematoxylin and Eosin [A] 100×, [B] 200×). Immunohistochemistry shows positivity of the remnant epithelial cells for
PanCK (C ), and the lymphoid cells for leucocyte common antigen (D ) (C, D 100×).
Fig. 5 Fine-needle aspiration cytology photomicrographs of the subsequent submandibular
swelling of the patient mentioned in Fig. 4 misdiagnosed as lymphoepithelial carcinoma
(May-Grunwald Giemsa [A ] 100×, [B ] 200×, inset 400×).
Fig. 6 Histopathological photomicrographs of the case shown in Fig. 5 conclusively diagnosed
as granulomatous lymphoepithelial sialadenitis (Hematoxylin and Eosin [A ] 40×, [B ] 10×, [C ] and [D ] 400×).
Discussion
Lymphocytic infiltrates of the salivary glands are discerned in a spectrum of diseases,
ranging from reactive to benign and malignant neoplasms. In many cases, the lymphocytic
infiltrate is a minor inflammatory component that is easily distinguished from the
primary disease processes. In some cases, however, the lymphocytic infiltrate emerges
as the major component of the disease. Histopathologic features that distinguish reactive
and benign lesions from malignant lesions are often subtle.[2 ]
Cases diagnosed as LELs encompassing benign LELs/lymphoepithelial sialadenitis/malignant
LELs and as poorly differentiated malignancies were keenly analyzed. Lymphoepithelial
sialadenitis is characterized by benign lymphocytic infiltrate of salivary gland with
parenchymal atrophy and foci of ductal hyperplasia with lymphocytic epitheliotropism.
The lobular architecture of the gland is usually preserved. In the early stages, the
extent of lymphocytic infiltrate varies among the lobules of the gland, but in late
stage disease, nearly all of the parenchyma is infiltrated with formation of lymphoid
germinal centers. Multiple foci of ductal epithelial hyperplasia are permeated by
lymphocytes, recognized as LELs.[2 ]
[3 ]
[4 ]
Biopsy was not warranted in most of the cases diagnosed as chronic sialadenitis. Two
cases diagnosed cytopathologically as chronic sialadenitis of the parotid gland turned
out to be benign salivary gland neoplasms on HPE—Warthin tumor and myoepithelioma.
Warthin tumors have a variable population of lymphoid cells, which proved to be the
diagnostic pitfall on FNAC.[5 ]
[6 ]
[7 ] Ductal cells with oncocytic features were not observed in the cytology sample. Conversely,
an inflammatory chronic sialadenitis that is lymphocytic rich may be misinterpreted
as Warthin tumor due to oncocytic metaplasia.[8 ] Myoepitheliomas can have a heterogenous appearance; subtypes of myoepitheliomas
are classified by cell morphology: spindle (interlacing fascicles with a stroma-like
appearance), plasmacytoid/hyaline (polygonal cells with eccentric nuclei and dense,
nongranular or hyaline, abundant eosinophilic cytoplasm), epithelioid (nests or cords
of round to polygonal cells, with centrally located nuclei and a variable amount of
eosinophilic cytoplasm), and clear (polygonal cells with abundant optically clear
cytoplasm, containing large amounts of glycogen but missing mucin or fat).[9 ] The spindle-shaped cells of myoepithelioma along with the lymphoid population posed
as the proverbial banana skin leading it to be misdiagnosed on FNAC as chronic sialadenitis
with fibrosis in this study.[10 ] Selective sampling is always an issue.
FNAC termed two cases of LECs, one arising from the minor salivary glands of the buccal
mucosa and another originating from the parotid as metastatic poorly differentiated
carcinomas. Thus, metastasis, especially from the nasopharyngeal carcinoma, can be
confused with the primary tumor even if the lesion involves the parotid. LEC, a rare
large cell undifferentiated carcinoma embedded within a dense lymphoid stroma, constitutes
only 0.4% of salivary gland neoplasms. The parotid gland is primarily affected, approximately
80% of cases, followed by the submandibular gland.[1 ]
[11 ] On cytopathology, the picture though can be heterogeneous. It may show a variable
admixture of neoplastic epithelial cells intimately admixed with a variable population
of lymphoid cells, or more commonly show a population of undifferentiated cells, which
may lead to other differential diagnoses such as poorly differentiated malignancy/poorly
differentiated carcinoma/metastatic carcinoma ([Fig. 7 ]). Conversely, the ductal cells of a benign process such as lymphoepithelial sialadenitis
or granulomatous lesion may look so atypical, so as to mimic LEC, and accordingly,
a granulomatous entity should also be kept in the differential diagnoses. The histiocytic
population may simulate neoplastic epithelial cells, as was the scenario in the previously
mentioned case of the 59-year-old female. Thus, caution should be exercised not to
misconstrue the histiocytic cells of granulomatous sialadenitis as that of poorly
differentiated epithelial lineage. Destruction of the salivary gland architecture
as seen in LECs is a morphologic feature in granulomatous/nongranulomatous lymphoepithelial
sialadenitis, as well as the infiltrating lymphoid population. IHC should be interpreted
appropriately correlating with the morphology and should not be regarded as the savior
to unraveling the diagnostic dilemma in such situations. Lymphoepithelial sialadenitis,
although it shares the prominent lymphoid population with LEC, lacks cytologic features
of malignancy, desmoplastic stroma, invasion of adjacent tissues, and EBV association.[2 ] Meticulous HPE is the sine qua non to solving such a diagnostic quandary.
Fig. 7 Fine-needle aspiration cytology photomicrographs of a case of lymphoepithelial carcinoma
misinterpreted as metastatic nasopharyngeal carcinoma (May-Grunwald Giemsa [A ] 200×, [B ] 400×).
As mentioned, metastatic carcinoma is another potential pitfall while dealing with
LECs. Presence of the infiltrating significant lymphoid population and/or associated
BLEL or lymphoepithelial nests similar to BLEL are helpful clues in differentiating
LECs from poorly differentiated malignancy/carcinoma and metastatic carcinoma, usually
from the nasopharynx ([Fig. 8 ]). In fact, the presence of accompanying BLEL is the most important finding in establishing
the histologic diagnosis of LEC. If, however, BLELs are absent, distinguishing LECs
from metastatic undifferentiated nasopharyngeal carcinoma can be quite challenging
on morphology as the two entities share similar cytologic, architectural, and immunohistochemical
features. Moreover, ethnic predilection and association with EBV infections are other
common threads between these two.[1 ]
[2 ] Fortunately though, the parotid gland is the predominant site of occurrence of LEC
and an infrequent site of metastasis from nasopharyngeal carcinoma, which more typically
metastasizes to the cervical or submandibular lymph nodes. IHC does not offer much
additional help in such cases. Careful clinical assessment and thorough evaluation
of the nasopharynx and Waldeyer’s ring region are essential to exclude the possibility
of metastatic disease (which is more common), and before accepting the salivary gland
tumor as primary LEC.[1 ]
[11 ]
Fig. 8 Photomicrograph of the corresponding tissue section of the case of lymphoepithelial
carcinoma mentioned in Fig. 7. Immunohistochemistry (IHC) for epithelial membrane
antigen (EMA) highlighting the epithelial nature of the large atypical cells (Hematoxylin
and Eosin [A ] 40×, [B ] 200×, [C ] 400×; IHC for EMA [D ] 100×).
IHC though helps differentiate LECs from other metastatic malignancies like amelanotic
melanoma or other carcinomas, and large cell lymphoid and histiocytic neoplasms.[12 ] Large cell undifferentiated carcinoma, which lacks histomorphologic features of
either glandular or epidermoid differentiation, is another differential diagnosis
of LEC. These are typically reactive for cytokeratins, but the prominent lymphoid
component of LEC as has been mentioned above again comes to the rescue in resolving
this conundrum, being absent in large cell undifferentiated carcinoma.[13 ] Not only this, the lymphoid stroma is also instrumental in limiting the aggressiveness
of LEC, perhaps contributing to the better prognosis of this carcinoma than the other
undifferentiated carcinomas of the salivary glands.[1 ]
The near 100% association of EBV with salivary gland LEC from the endemic areas and
the presence of the virus in a clonal episomal form suggest an important role of EBV
in tumourigenesis.[11 ]
[14 ]
[15 ]
[16 ] In our study, however, IHC detected expression of EBV-LMP1 in the tumor cells in
only two out of five cases of LEC (40%). In-situ hybridization is more sensitive in
proving this association, by detection of EBV-encoded RNA and EBV-DNA in the tumor
cells. IHC expression of EBV-LMP1 is more variable, thus clarifying the reason for
the negativity of EBV-LMP1 in the three cases, and the unlikely low association in
an otherwise endemic area. In patients from nonendemic areas, EBV is usually absent,
although rare cases may harbor the virus. These findings indicate complex interactions
of ethnic, geographic, and viral factors in the pathogenesis of salivary gland LEC.[11 ]
[14 ]
[15 ]
[16 ]
[17 ] LECs have a strong tendency to metastasize to the regional cervical lymph nodes,
and approximately 20% develop distant metastasis, most commonly to the lung, liver,
bone, and brain. However, 75 to 86% of patients are documented to survive when treated
with surgery, including neck dissection, and radiation therapy, although local recurrence
can occur.[11 ]
[15 ]
[16 ]
[18 ]
Conclusion
LELs of salivary glands can pop up as a pathologist’s quagmire at times. This study
tried to highlight the diagnostic issues related to these lesions, both from a cytopathologic
and a histopathologic perspective. LECs can mimic undifferentiated carcinoma, metastatic
carcinoma, or even reactive/granulomatous lesions not only on cytology but also on
HPE of the excised lesion. Even benign salivary gland tumors can be masked by chronic
sialadenitis/LELs. Careful attention to pathologic detail and clinical inputs is the
cornerstone in arriving at the correct diagnosis, thus paving the way for appropriate
management.
