1. Minor salivary gland neoplasms can be difficult to diagnose based on limited tissue sampling from biopsies due to overlapping histological features between benign and malignant tumors. 2. Both benign and malignant tumors may appear circumscribed and show similar growth patterns, cytomorphology, stroma, and immunoreactivity, limiting the ability to render a specific diagnosis. 3. A diagnosis of mucoepidermoid carcinoma can generally be made on biopsy due to its characteristic cell types, but distinction between other tumors often requires examining features of invasion in completely excised specimens.

1. Pitfalls in the Biopsy Diagnosis Of Intraoral
Minor Salivary Gland Neoplasms: Diagnostic
Considerations and Recommended Approach
(Adv Anat Pathol Volume 21, Number 1, January
2014)
BY EKTA JAJODIA

2. Sites of minor salivary glands
-Most numerous at junction of hard and soft palate
-Buccal mucosa
-Lips
-Tongue
All of these glands are predominantly mucous
VON EBNER’S GLANDS – these are purely serous
Located in dorsum of tongue in relation to
circumvallate papillae
Minor salivary glands are not encapsulated

3. Intraoral minor salivary gland neoplasms include
• Benign tumors -
1.Pleomorphic adenoma
2.Monomorphic adenoma, basal cell type (also
known as basal cell adenoma)
• Malignant tumors-
1.Mucoepidermoid carcinoma
2.Adenoid cystic carcinoma
3.Polymorphous low-grade adenocarcinoma

4. • Initial diagnostic modality for a patient with an
intraoral mass - fine-needle aspiration biopsy or
incisional biopsy
• Limitations-
1. Small tissue sampling
2. Similar growth patterns
3. Similar cytomorphology
4. Similar immunoreactivity
Both benign
and malignant

5. Exception to this problem- Mucoepidermoid
carcinoma(MEC)
Characterized by mucocytes, epidermoid cells, and
intermediate cells
As no other salivary gland neoplasm consists of
these cellular components, identification of these
cell types permits a diagnosis of MEC even in
context of limited sampling

6. Other intraoral minor salivary gland tumors share
light microscopic and IHC features
Distinction between benign and malignant lesions
depends upon identification of invasive growth
But incisional biopsy of intraoral minor salivary gland
tumors consists of lesional material without
surrounding tissues - assessment of invasive growth
cannot be done
So specific diagnosis rendered on the basis of FNAB
or incisional biopsy may result in discordant
diagnosis after complete surgical resection

7. 1. Circumscription without encapsulation
2. Multiple growth patterns
3. Bland cytomorphology
4. Combination of epithelial and myoepithelial cell
differentiation
5. Absent to minimal increase in mitotic activity
6. To a large extent similar IHC reactivity
Shared findings among minor salivary
gland neoplasms

8. A and B, Incisional biopsy shows a cellular neoplasm comprised of
tubules with isomorphic basaloid-appearing nuclei without features
allowing for determining whether it is benign or malignant. C, After
complete excision showing circumscription without invasion, a
diagnosis of basal cell adenoma can be rendered

9. Circumscription, Encapsulation, and
Invasive growth
• All minor salivary gland neoplasms, whether
benign or malignant, are unencapsulated
So presence or absence of capsule does not
differentiate benign and malignant minor salivary
gland tumors
• Both benign and malignant intraoral minor salivary
gland neoplasms may be circumscribed

10. Extension of tumor to (and even involvement of)
surface (squamous) epithelium does not represent
criterion for malignancy
Malignant lesions show invasive growth, including
invasion into non-neoplastic seromucous glands ,
soft tissues , perineural invasion (PNI) , and lymph-
vascular invasion (LVI)
But such findings are uncommon in small biopsies
of intraoral minor salivary gland neoplasms

11. All minor salivary gland neoplasms are unencapsulated and often
even malignant neoplasms such as polymorphous low-grade
adenocarcinoma appears circumscribed in its superficial aspect

12. Pleomorphic adenoma showing lesional cells extended to and even
involvement of the surface (squamous) epithelium. This finding is not
diagnostic for malignancy

13. GROWTH PATTERN
Salivary gland neoplasms of both major and minor
salivary gland show >1 growth pattern including
tubular-ductular, solid, (micro)cystic, cribriform,
trabecular, nodular, lattice-like, fascicular, and/or
papillary
Cribriform growth may suggest a diagnosis of
adenoid cystic carcinoma, but is not pathognomonic
of this lesion
This finding may also be present in other intraoral
minor salivary gland neoplasms including PLGA,
pleomorphic adenoma and basal cell adenoma

15. 1. Swirling or whorling patterns (often at the lesion’s
periphery)
2. Show single-file formations of tumor cells (akin to
lobular carcinoma of the breast)
3. Incorporation of non-neoplastic seromucous
glands (while pleomorphic adenoma, basal cell
adenoma, and adenoid cystic carcinoma generally
cause architectural effacement such that residual
seromucous glands cannot be identified within the
tumor
Characteristic features of Polymorphous
low-grade adenocarcinoma

16. Diagnosis of PLGA(ie, diagnosis of minor
salivary gland carcinoma) requires identification of
PNI, LVI, and/or invasive growth
Nuclear palisading of basaloid cells along the
stromal interface is often seen in basal cell
adenoma, although this feature is not specifically
diagnostic of basal cell adenoma
Intraoral minor salivary gland tumors show
architectural overlap to permit definitive diagnosis
based on any single growth pattern, or combination
of architectural features

17. • Adenoid cystic carcinoma characteristically
contains abundant myoepithelial (abluminal) cells
with increased nuclear-to-cytoplasmic ratio, and
basaloid (hyperchromatic) angulated nuclei without
identifiable nucleoli
• Similar nuclear features can be present in basal cell
adenoma and even in pleomorphic adenoma
• But basaloid hyperchromatic nuclei are not evident
in PLGA which typically consists of cells with
vesicular chromatin and inconspicuous
small nucleoli
CYTOMORPHOLOGY

18. • Although myoepithelial cells are predominant
in basal cell adenoma and adenoid cystic carcinoma,
these tumors may display small ductular or tubular
structures lined by luminal cells with round-to-oval
nuclei and eosinophilic cytoplasm
• In basal cell adenoma, ductal (luminal) cells are
most conspicuous in the tubular subtype
• Myoepithelial cells can be present in all the above
tumor types, although myoepithelial cells are not
characteristic of PLGA

19. • Neoplastic (modified) myoepithelial cells may
display various morphology including plasmacytoid,
spindle shaped (so-called “hyaline cells”) ,
epithelioid, cuboidal, stellate, or clear cells
• Plasmacytoid myoepithelial cells often occur in
pleomorphic adenoma and may be informative in
limited tissue sampling, although they are not
pathognomonic

20. A- In adenoid cystic carcinoma, small ductular or tubular structures lined by luminal
cells among the predominant myoepithelial (abluminal) cell type.
B- Ductular or tubular structures are readily apparent in this basal cell adenoma,
tubular subtype

21. PLGA show characteristic but not pathognomonic growth patterns including: (A)
swirling/whorling cellular arrangements at the lesion’s periphery (B) single cell file
formation (akin to lobular carcinoma of the breast (C) incorporation or envelopment
(rather than effacement) of residual non-neoplastic seromucous gland

22. A- In adenoid cystic carcinoma, the predominant cell type is the myoepithelial
(abluminal) cells comprised of isomorphic, basaloid (hyperchromatic), and angulated
nuclei without identifiable nucleoli. B- Polymorphous low-grade adenocarcinoma
also comprised of isomorphic nuclei but in contrast show vesicular appearing
nuclei with small identifiable nucleoli.

23. A- The presence of squamous eddies (with and without keratinization) seen in basal
cell adenoma B- Plasmacytoid cells in pleomorphic adenoma C- spindle shaped in
pleomorphic adenoma

24. • Chondromyxoid stroma - definitive histologic
component of pleomorphic adenoma
Facilitates distinction of pleomorphic adenoma from
monomorphic adenoma
• Due to limitations of tissue sampling,
chondromyxoid stroma of PA may not be present
• Consequently, absence of chondromyxoid stroma
does not preclude a diagnosis of PA, nor should lack
of it prompt a diagnosis of monomorphic adenoma
• It may appear similar to the slate blue-gray
mucohyaline matrix sometimes seen in PLGA
TUMOR STROMA

25. • Adenoid cystic carcinoma shows pseudocysts with
basophilic and eosinophilic-appearing material
• Hyalinized (collagenized) stroma can be seen in
basal cell adenoma, particularly the membranous
subtype as well as in PA and adenoid cystic
carcinoma
• Basal cell adenoma sometimes shows small
“droplets” of matrix within nests of neoplastic cells
• Stromal features are useful but definitive diagnosis
cannot be based on it

26. A,B – chondromyxoid stroma of PA
C – Blue gray appearing stroma in PLGA
D - Adenoid cystic carcinoma showing basophilic and focally slightly
eosinophilic material within the pseudocysts

27. Basal cell adenoma. A, Membranous subtype showing islands of basaloid cells
surrounded by thick extracellular hyalinized (basement membrane) material. B,
Small “droplets” of membranous matrix material within nests of basaloid
neoplastic cells.

28. • Metaplasia may occur spontaneously or after FNAB
• Squamous metaplasia in the form of cells with
keratinization and intercellular bridges are seen in
PLGA, PA and membranous variant of BCA
• In contrast to other tumor types, adenoid cystic
carcinoma rarely displays squamous metaplasia
So, metaplasia may be informative, particularly in
ruling out adenoid cystic carcinoma
METAPLASIA

29. • These neoplasms are frequently devoid of mitotic
activity by light microscopy
• Malignant lesions may show marked increase in
mitotic activity with atypical mitoses, but mitotic
figures do not distinguish malignant lesions from
their benign counterparts
• Ki-67 (MIB-1) IHC also does not definitively
distinguish adenoid cystic carcinoma and/or PLGA
from PA or basal cell adenoma
So Ki-67 IHC is of limited value in the distinction of
these tumors
MITOTIC ACTIVITY

30. MISCELLANEOUS FINDINGS
Tyrosine-rich crystalloids - characteristic of
Pleomorphic adenoma but may also be seen in
PLGA and other tumors
Psammomatoid concretions can be present in a
variety of salivary gland neoplasms like
PLGA, pleomorphic adenoma, and monomorphic
adenoma

31. HISTOCHEMISTRY
• All of these lesions lack intracytoplasmic mucin -
show negative intracytoplasmic staining with
mucicarmine
• But, any of these lesions may contain extracellular
(eg, intraluminal) mucicarmine positive material
• Any of these lesions may also show
intracytoplasmic glycogen (ie, positive
intracytoplasmic staining with DPAS).

32. IHC markers for epithelial component include –
1. Low–molecular weight cytokeratins (eg, CK7,
CK19, and CAM5.2)
2. Epithelial membrane antigen(EMA)
3. Carcinoembryonic antigen(CEA)
CD117/c-kit is negative in normal salivary gland
cells but is positive in luminal cells of various
salivary gland tumors
IMMUNOHISTOCHEMISTRY

33. All the above mentioned tumors show both epithelial
and myoepithelial components and also share
overlapping IHC features
So IHC does not generally facilitate distinction
between these lesions
IHC markers for myoepithelial component include-
1.high–molecular weight cytokeratin
2.Vimentin
3.p63
4.Calponin
5. muscle-specific and smooth muscle actin (SMA)
6. S100 protein
7. glial fibrillary acidic protein (GFAP)
8.maspin(serine protease inhibitor)

34. • The only IHC stain that might prove beneficial in
limited biopsies is S100 - to identify neurotropism- a
finding that would confer a diagnosis of carcinoma
• However, the absence of PNI in limited tissue
sampling does not exclude a diagnosis of carcinoma
• c-Kit (CD117) IHC – potential marker of adenoid
cystic carcinoma
• Differences in c-Kit staining represent the most
striking distinction between adenoid cystic
carcinoma and PLGA, suggesting potential utility of c-
Kit in the evaluation of small biopsies

35. NEOPLASM CHROMOSOMAL
TRANSLOCATION
GENE FUSION
PA 8q REARRANGEMENT PLAG1
12q REARRANGEMENT HMGA2
MEC t(11;19) CRTC1-MAML2
AdCC t(6;9) MYB-NFIB
HCCC t(12;22) EWSR1-ATF1
MASC t(12;15) ETV6-NTRK3
MOLECULAR GENETICS

36. Recommendations for the Diagnosis
of Intraoral Minor Salivary Gland
Neoplasms
• Presence of metastatic disease would be diagnostic
for a malignant neoplasm, but most intraoral minor
salivary gland carcinomas, including PLGA and
adenoid cystic carcinoma (as well as low-grade
mucoepidermoid carcinoma), are infrequently
associated with metastatis at time of diagnosis
• Also definitive features of malignancy are
predicated on infiltrative growth

37. • Infiltrative growth includes invasion into non
neoplastic seromucous glands, soft tissues and/or
bone, PNI, and LVI
By definition, invasive growth occurs at a lesion’s
periphery
Due to limited sampling of the lesion’s periphery,
invasion cannot be assesed
• Due to histopathologic and IHC overlap between
various intraoral minor salivary gland neoplasms
interpretation of incisional biopsies is complicated
• In this scenario, pathologists are advised to render
relatively broad diagnosis while providing as much
information as feasible regarding differential
diagnosis

38. • When such cases which lack overtly malignant
features, but does not permit
exclusion of malignancy, appropriate diagnostic
terminology would resemble “Minor salivary gland
neoplasm, not further specified,” with
recommendation of conservative but complete
surgical excision with tumor-free margins
• On basis of limited material, a more specific
diagnosis whether benign or malignant, may be
discordant with diagnosis resulting from a
subsequent resection specimen

39. CONCLUSION
• Limited biopsies of intraoral minor salivary gland
neoplasms are frequently insufficient for definitive
diagnosis
• Our clinical colleagues may believe that biopsy
material should facilitate distinction between benign
and malignant neoplasms
• Unfortunately, this expectation is frequently
unrealistic due to sampling issues

40. • Terminology such as “Minor salivary gland
neoplasm, not further specified,” should be used,
confirming presence of a neoplastic proliferation that
necessitates complete surgical resection with clear
margins
• After resection, evaluation of excised specimen
facilitates assessment of invasive growth, and
establishment of definitive diagnosis
• An intraoral minor salivary gland neoplasm lacking
invasive growth is benign (eg, pleomorphic adenoma
or basal cell adenoma)
• Complete resection of benign tumors is curative

41. • Identification of invasive growth warrants a
malignant diagnosis (eg, PLGA or adenoid cystic
carcinoma)
• In case of PLGA, complete resection with tumor-free
margins is considered curative and additional therapy
(eg, radiotherapy) is generally not
indicated
• Potential complications of radiotherapy in the
setting of PLGA may include osteoradionecrosis
• Adenoid cystic carcinoma, in contrast, necessitates
adjuvant therapy, specifically radiation, in addition to
complete surgical resection

42. MAMMARY ANALOGUE SECRETORY
CARCINOMA (MASC)
• To date, approx 70 reported cases
• M:F – 1.5:1
• Majority of cases reported in major salivary glands
• ETV6-NTRK3 gene fusion – hallmark
factor/pathognomonic for differentiating MASC
from other salivary gland tumors

43. MICROSCOPICALLY –
1. Lobulated growth pattern c/o microcystic,
tubular and papillary structures
2. Vesicular nuclei, centrally placed nucleoli and
finely vacuolated/ granular eosinophilic
cytoplasm
3. Abundant eosinophilic secretory material within
luminal spaces
4. No necrosis, atypical mitosis or pleomorphism
IHC- Neoplastic cells strongly positive for Cam5.2 ,
S-100 and vimentin
PAS and PAS-D highlight the luminal material

44. D/D-
1. PLGA (MASC weakly stains for Ki-67 while PLGA
strongly stains for Ki-67 and GFAP)
2. Low grade cribriform cystadenocarcinoma

45. A- Microcystic pattern with eosinophilic luminal secretions
B- solid sheets of tumor cells
C- bland vesicular nuclei
D- vacuolated cytoplasm seen

46. INFLAMMATORY MYOFIBROBLASTIC
TUMOR (IMT)
• Previously known as inflammatory pseudotumor –
as tumor like conditions
• Added as IMT in the AFIP series 4
• Tumor with intermediate or low malignant
potential
Other sites- Lung, mesentery , omentum
MICROSCOPICALLY-
1. Circumscribed but unencapsulated
2. Spindle shaped myofibroblasts arranged in
storiform / fascicular pattern
3. Inflammatory infiltrate composed of lymphocytes,
plasma cells and eosinophils
4. Myxoid to hyaline stroma

47. D/D –
1. Leiomyoma
2. Leiomyosarcima
3. Nodular fascitis
4. Myofibroma
• All of this lack the inflammatory cell component
of IMT
• Inflammatory cells seen in nodular fascitis but
lymphocytes, rather than plasma cells
predominate
• IHC- spindle cells in IMT shows positive for SMA
- About half of the tumors show positive for
Anaplastic lymphoma kinase 1(ALK)

48. IMT – numerous inflammatory cells among spindle cells

49. SCLEROSING MUCOEPIDERMOID
CARCINOMA WITH EOSINOPHILIA
• Uncommon tumor of thyroid gland
• 2 cases reported as primary tumor of major
salivary gland
• Behave as low grade malignant neoplasm
• Unclear whether a distinctive tumor type or a
variant of conventional MEC
1. Sclerotic stroma heavily infiltrated by chronic
inflammatory cells and eosinophils
2. Island and trabeculae of tumor cells which have
a squamoid appearance and focal keratinisation
3. Admixed mucinous cells and glandular
structures seen

50. SCLEROSING MUCOEPIDERMOID CARCINOMA WITH EOSINOPHILIA

51. KERATOCYSTOMA
• Very rare benign tumor with only 3 cases
reported
• Histologically mistaken for a well differentiated
squamous cell carcinoma
• Grossly, tumor is a multilocular cystic lesion filled
with creamy material
Histologically –
1. Randomly distributed cystic and solid nests of
squamous cells

52. 2. Cysts are lined by bland looking stratified
squamous epithelium with ortho- and
parakeratosis and lacking a granular layer
3. Lumens are filled with lamellated keratin
4. Epithelium is demarcated from fibrotic stroma
by basement membrane
5. Foreign body giant cell reaction may be
present against keratin extruded from ruptured
cyst

53. Showing multiple cystic formations filled with lamellar keratin
material

54. A- variably sized and shaped cystic lesions filled with lamellar keratin material
B- Portion of the cyst wall showing stratified squamous epithelium with
keratinization and parakeratotic cells. Note the lack of a granular cell layer
C- Solid squamous cell islands with sharply defined margins enclosed within
collagenous stroma
D- Solid masses composed of squamous epithelium in conjunction
with parotid ducts. Note a residual duct lumen in squamous cell nests

55. CRIBRIFORM ADENOCARCINOMA OF
THE TONGUE
• Unclear whether a distinct tumor type or a
variant of PLGA
• Occurs exclusively in base of tongue
• Frequency of cervical lymph node metastasis at
presentation is high
1. Diverse growth patterns like solid, microcystic,
cribriform and papillary
2. Tumor cells are bland looking and possess
uniform nuclei with ground glass/vesicular
chromatin
3. No significant mitotic activity, hemorrhage or
necrosis

56. Cribriform adenocarcinoma of the tongue. The tumour is characterized by
invasive cribriform islands comprising cells with uniform ground glass nuclei
and low mitotic activity

57. THANK
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