diagnostic pitfalls in uterine tumors of mesenchymal origin and how to differentiate between them with the aid of IHCs and molecular studies

1. Diagnostic Challenges In Uterine
Mesenchymal Tumors
Muneerah Saeed

2. MESENCHYMAL TUMORS OF THE UTERUS
Smooth muscle neoplasms
• Most common
• Majority- benign-
Leiomyoma
• MC-malignant-
Leiomyosarcoma; >50%
uterine sarcoma; 1-2%
uterine malignancy
Endometrial
stromal neoplasms
• 2nd most
common
Others

3. Mesenchymal tumors
Leiomyoma
 Cellular
 Leiomyoma with bizarre nuclei
 Mitotically active
 Hydropic
 Apoplectic
 Lipomatous (lipoleiomyoma)
 Epithelioid
 Myxoid
 Dissecting (cotyledonoid)
 Diffuse
 Intravenous
 Metastasizing
Smooth muscle tumor of uncertain
malignant potential
Leiomyosarcoma
 Epithelioid leiomyosarcoma
 Myxoid leiomyosarcoma
Endometrial stromal and related tumors
Endometrial stromal nodule
Low-grade endometrial stromal sarcoma
High-grade endometrial stromal sarcoma
Undifferentiated uterine sarcoma
Uterine tumor resembling ovarian sex cord Tumor
Miscellaneous mesenchymal tumors
Rhabdomyosarcoma
Perivascular epithelioid cell tumor
• Benign/Malignant
Others
Mixed epithelial and mesenchymal tumors
Adenomyoma
Atypical polypoid adenomyoma
Adenofibroma
Adenosarcoma
Carcinosarcoma
WHO(2014) Classification Of Tumors Of The Uterine Corpus

4. GROSS EXAMINATION
 Macroscopic examination of mesenchymal tumors cannot be overemphasized
 Typical fibroids, up to 3 of the largest tumors- hysterectomies and every fragment- myomectomy
specimens
 Diligent sampling- Deviations from usual gross appearance
 “Degenerative” changes
 Variant
 Malignancy
 Exogenous hormonal preparations
 Sections of the tumor/myometrial interface- most rewarding- diagnostically challenging
tumors- irregular, infiltrative border/ vascular invasion identified
 Multiple appropriately sampled sections are all that is frequently required in problematic
cases to enable a definitive diagnosis to be made.

5. GROSS PATHOLOGICAL FEATURES LEIOMYOMA COMPARED WITH LEIOMYOSARCOMA

6. Hydropic features centrally with microcyst
formation, characteristic- Ulipristal acetateYellow cut surface of lipoleiomyoma

7. Cellular leiomyoma- yellow cut surface
Endometrial stromal nodule: neoplastic stroma-
distinctive yellow appearance + smooth muscle
differentiation- tan areas
• Yellow
• Lack characteristic
whorled bulging
appearance
-Cellular leiomyoma:
Myometrium
-ESN: Softer,
endometrium

8. Endometrial stromal sarcoma,
low-grade- intracavitary polypoid
mass - numerous soft yellow tan
nodules
Endometrial stromal sarcoma,
high grade- polypoid intracavitary
mass- extensive hemorrhage
Undifferentiated uterine
sarcoma

9. Endometrial stromal tumors
Endometrial
stromal nodule
Low-grade endometrial
stromal sarcoma
High-grade endometrial
stromal sarcoma
Undifferentiated uterine
sarcoma
Uterine tumor resembling
ovarian sex cord Tumor

10. Endometrial Stromal Nodule
 Characterized by sharp circumscription between the neoplastic cells and surrounding endometrium
or myometrium, with a pushing interface
 Sometimes, finger-like extensions into surrounding myometrium, but these foci should be <3 in
number & < 3 mm from the main mass; otherwise low grade ESS
 No lymphatic or vascular invasion is present
 Resembles proliferative phase endometrial stroma
 These cells appear to whorl around the prominent vascular component, which resembles the spiral
arterioles of non-neoplastic endometrium
 Foamy stromal cells may be conspicuous

11. Foamy cells are a characteristic
characteristic cytomorphology and
vasculature
well-demarcated border with the
myometrium
Endometrial Stromal Nodule

12. Low-Grade Endometrial Stromal Sarcoma
 Women with low-grade ESS are typically perimenopausal but tend to be younger
than those who present with other types of uterine sarcoma
 Histologically, low-grade ESS cells morphologically indistinguishable from ESN
 Generally low mitotic rate & necrosis uncommon
 ESN and low-grade ESS, can occasionally exhibit a diverse range of differentiation
including sex cord–like, epithelial (e.g., endometrioid type glands), smooth
muscle, and, rarely, skeletal muscle differentiation

13. Endometrial stromal sarcoma, low
grade. Shown is vascular invasion
Mixed endometrial stromal–smooth
muscle tumor. An area of smooth muscle
differentiation
Endometrial stromal sarcoma, low
grade. Ovarian sex cord–like
Prominent endometrioid glandular
differentiation

14. Ddx-Highly cellular leiomyoma

15. High-Grade Endometrial Stromal Sarcoma
 Histologically, the tumor shows extensive finger-like permeation of the myometrium and
lymphovascular invasasion
 The tumor typically contains morphologically low- and high-grade areas

16. biphasic growth-morphologically
low-grade & high-grade
component
Morphologically low-grade areas
have a similar appearance to
fibromyxoid variant of a low-grade
ESS
high-grade areas, tumor cells appear
epithelioid, with more vesicular
nuclei, mitotic activity and
karyorrhexis.
High-Grade Endometrial Stromal Sarcoma

17. Undifferentiated Uterine Sarcoma
 Neoplastic cells show marked cellular atypia and numerous mitoses, including atypical
forms, without evidence of differentiation toward endometrial stroma both
cytomorphologically
 Diffuse and destructive infiltrative pattern as opposed to the characteristic
wormlike pattern and propensity for intravascular extension characteristic of
low-grade ESS
 Differential diagnosis: poorly differentiated carcinoma, leiomyosarcoma, and
carcinosarcoma, all of which may be morphologically similar in appearance

18. Undifferentiated Uterine Sarcoma
Undifferentiated uterine sarcoma. A pleomorphic sarcoma
with numerous, often atypical, mitoses

19. Immunohistochemistry In Endometrial Stromal Tumors
 Frequently positive for cd10, ER, PR. High grade endometrial stromal sarcoma with t(10;17) and
undifferentiated endometrial sarcomas, are ER and PR negative
 Can be positive for actin and keratin
 Desmin and h-caldesmon are generally negative. But are typically positive in areas showing smooth-
muscle differentiation and often positive in areas of sex cord-like differentiation.
Marker LG-ESS HG-ESS UUS LM/LMS
CD10 ++ +/- Patchy +/-
Desmin +/- +/- ++
H-caldesmon +/- +/- ++
ER ++ +/- Patchy +/-
PR ++ +/- Patchy +/-
Cyclin D1 - ++ +/-
CD117 +

20. UTERINE SMOOTH MUSCLE TUMORS
Leiomyoma(benign)
 Cellular (highly) LM
 LM with bizarre nuclei
 Mitotically active LM
 Myxoid LM
 Hydropic LM
 LM with heterologous elements
(lipoLM)
Leiomyosarcoma
(50% 5-year survival)
• Epithelioid LMS
• Myxoid LMS
STUMP
Intravascular Leiomyomatosis
Diffuse peritoneal Leiomyomatosis
Benign metastasizing LMUterine

21. DIAGNOSTIC CHALLENGES IN UTERINE SMOOTH MUSCLE TUMORS
TYPICAL LEIOMYOMA
- Not problematic
 Variable amounts of collagenous tissue-
initially in between smooth muscle
cells; later replacing smooth muscle
cells.
 Extensive hyalinization- difficult to
recognize- as a smooth muscle
neoplasm. Usually postmenopausal-
both dystrophic calcification and
ossification.

22. LEIOMYOSARCOMA
The 3 principal factors in the determination of malignancy:
 Obvious proliferative activity- Increased mitotic figures
 Significant nuclear and cytologic atypia
 Cellular instability- particular pattern of necrosis.
In addition, these tumors may be hypercellular and infiltrate into
surrounding myometrium.

23. Evaluation of Mitotic Activity
 Typically, Mitotic figures counted in adjacent high-power fields(Recommended ≥30) and
averaged over 10 hpf. Note mitotic rate of proliferative hot spots when found.
 Diagnostic pitfall: Care must be taken that the mitoses are not counted adjacent to a zone of
ulceration and regeneration. This pitfall is usually seen in a benign submucosal leiomyoma
exposed to traumatic injury
 Most important prognostic factor identified histologically. Use of Ki-67 antigen, IHC surrogate
for counting mitotic figures, is far less clear. Another proliferation marker, phosphorylated
histone H3; produces counts comparable to the H&E gold standard for leiomyoma but tends to
inflate counts for leiomyosarcoma.

24.  Each potential mitotic figure must be carefully scrutinized to ensure that it is not a
degenerating cell.
 Such mimics, with pyknotic nuclei are common in benign and malignant tumors
 Casual counting may drastically overestimate proliferation in a given tumor

26. Evaluation of Cytologic Atypia
 Significant(Moderate or Severe) nuclear atypia- the atypia should be notable at low (10× objective)
power
 The degree of nuclear atypia found in leiomyosarcomas spans a wide spectrum: pleomorphic tumor
cells also may resemble trophoblastic malignancy, inflammatory giant cells or osteoclasts
 May also be manifested in leiomyosarcoma by divergent (heterologous) patterns of differentiation,
which may include osteosarcomatous, rhabdomyosarcomatous, and chondrosarcomatous foci

27. Leiomyosarcoma with extreme nuclear
atypia resembling malignant
trophoblasts
Osteosarcomatous differentiation in
leiomyosarcoma
Atypical giant cells in a
leiomyosarcoma

28. Evaluation of Tumor Cell Necrosis
• Of the three principal factors, tumor necrosis
carry the greatest weight in the determination
of malignancy
• Malignancy-associated tumor necrosis has
to be carefully distinguished from benign
degenerative changes and other
therapeutic effects.
• Difficult to classify - subjective as well as
degenerative processes need not be limited to
benign tumors, and mixed patterns of necrosis
in a malignant tumor may be confusing

29. Infarct type necrosis: poorly demarcated zone between the viable tumor cells and central degenerative area, with
hyalinization and hemorrhage
Geographic tumor cell necrosis: Sharp line of demarcation of island like zone of tumor & Atypical ghost cell

30. DIFFERENTIAL DIAGNOSIS OF LEIOMYOSARCOMA
 Leiomyoma with infarction
 Mitotically active leiomyoma
 Leiomyoma with bizarre nuclei
 Smooth Muscle tumor of Uncertain Malignant Potential(STUMP)
 High grade Stromal sarcoma

31. Ddx- Mitotically Active Leiomyoma
Mitotically active leiomyoma LMS
Grossly appear same as usual leiomyoma. Smaller and well
circumscribed
Variegated appearance with areas of necrosis and
hemorrhage. large
Women younger than 35 years Older women
Most cases asso. with secretory endometrium -suggesting
increased mitotic activity- progesterone related effect. Use of
exogenous progestogens- implicated as a cause of increased
proliferation.
No such association
Mitotic activity 5-14/10HPF Mitotic activity ≥ 10/ 10HPF
No necrosis or atypia(focal bizarre nuclei may be seen) Necrosis and/or atypia present

32. Ddx- Leiomyoma With Bizarre Nuclei
 Presence of ≥ 5% multinucleated, multilobated or mononucleated bizarre giant nuclei with prominent
smudged and clumped nuclear chromatin. Intranuclear eosinophilic cytoplasmic pseudo-inclusions
seen within the bizarre nuclei.
 Reactive to p16 (86.5%) & p53(60%). Nearly half show over 10% positive for Ki-67. Therefore; these
have a limited role in distinguishing these two tumors
LBN LMS
Bizarre cells distributed either focally or multifocally lying
in a background of smooth muscle cells of usual type
background cells are usually all cytologically atypical
when scrutinized at high power magnification
Hypercellular Hypercellular
No increase in mitosis. Degenerative changes seen within
atypical nuclei. Karyorrhectic nuclei seen
Increased mitosis seen
Infarct type necrosis may be seen Tumor necrosis seen

33. Leiomyoma with bizarre nuclei
Leiomyosarcoma, background cells all pleomorphic
with
multinucleated bizarre cells with several mitotic
figures

34. FH- Deficient Leiomyoma
 Leiomyomata associated with a mutation of Fumarate hydratase (FH)- overlapping
features with leiomyoma with bizarre nuclei
 seen in younger women <40 years of age as multiple leiomyomata
 Mostly sporadic- may carry a germline mutation of FH associated with the HLRCC
(hereditary leiomyomatosis and renal cell carcinoma syndrome)
 . FH & S-(2-succino)-cysteine (2SC) can be detected immunohistochemically

35. Show increased cellularity, staghorn vessels, neurilemmoma-like nuclear palisading and
prominent inclusion-like eosinophilic macronucleoli with a perinuclear halo. Nuclear
atypia and multinucleation
Neurilemmoma like areas of nuclear palisading
FH deficient leiomyoma with perinuclear haloes
and eosinophilic inclusions

36. Ddx- Smooth Muscle tumor of Uncertain Malignant Potential
(STUMP)
• Few tumors have phenotypic features between the benign variants and the
leiomyosarcomas.
• When the problem of classifying tumors with intermediate morphologic features
was appreciated, a new diagnostic category was introduced—STUMP

37. Epithelioid Leiomyosarcoma
 Rounded, nonspindled tumor cells with abundant eosinophilic cytoplasm
 May have reduced expression of smooth muscle markers (e.g., desmin, h-caldesmon). application
of another marker of smooth muscle differentiation, histone deacetylase 8 (HDAC8), may be helpful

38. Epithelioid Leiomyosarcoma Epithelioid Leiomyoma
Epithelioid Leiomyosarcoma

39. Differential Diagnosis of Epithelioid Leiomyosarcoma
 Epithelioid leiomyoma
 Epithelioid ESS
 Perivascular Epithelioid Cell Tumor (PEComa)
 Other Sarcomas with epithelioid/ rhabdoid morphology

40. Ddx- Perivascular Epithelioid Cell Tumor (PEComa)
 These are rare mesenchymal tumors of the FGT, MC- affecting the uterus
 Characteristically they co-express melanocytic and muscle markers
 Important to dx- respond to mTOR inhibitor therapy
 Characterised predominantly by epithelioid, clear cell morphology and without pleomorphism
and an IHC
 positivity: HMB45, TFE3 and cathepsin K
 negativity for MiTF, SMA and desmin

41. (a) PEComa cords of cells with clear cytoplasm. (b) PEComa with
immunopositivity for HMB45. (c) PEComa showing positive
immmunoreactivity for TFE3

42. Myxoid Leiomyosarcoma
 Rare variant of uterine leiomyosarcoma
 The increased extracellular matrix reduces cellularity and consequently counts of mitotic activity.
 Myxoid leiomyosarcoma diagnosed with any one of the following features:
(1) more than 2 mitoses/10 hpf; (2) significant cytologic atypia;
(3) tumor cell necrosis; and (4) destructive infiltration of adjacent myometrium

43. Myxoid Leiomyosarcoma
Infiltrating tumor cells permeating through myometrial
fascicles
loose collection of atypical cells and an occasional
mitotic figure (center and inset) in a rarified stroma.

44. Differential diagnosis of Myxoid Leiomyosarcoma
 Inflammatory Myofibroblastic Tumor (IMT)
 Hydropic leiomyoma
 Myxoid ESS

45. Ddx- Inflammatory Myofibroblastic Tumor (IMT)
 mesenchymal tumor of low malignant potential. It shows a
cellular proliferation of spindled to epithelioid cells in a myxoid
stromal background.
 a conspicuous lymphoplasmacytic infiltrate within the neoplasm
 Absence of IHC anaplastic lymphoma kinase (ALK) staining or
ALK gene rearrangement by FISH
IMT Myxoid leiomyosarcoma
No evidence of aberrant
immunoreactivity with p53
50% showed aberrant expression of p53,
the most common being a “null” pattern
Patchy, heterogenous reactivity with P16. Abnormal P16 (strong and diffuse)
observed in 70%
Inflammatory myofibroblastic tumor:
myxoid stromal background

46. Ddx- Hydropic leiomyoma
• Grossly, the wet, slippery, cut surface can be described as “myxoid”. Histologically
examined to exclude a myxoid leiomyosarcoma by recognizing their edematous
nature and lack of other malignant features
• Hydropic degeneration may be worrisome at lower magnifications- irregular contours
and sharper borders
• Careful attention at higher magnifications often resolves this by noting the fluid-filled
intercellular spaces and the absence of truly necrotic cells.

47. Immunohistochemistry in Smooth muscle tumor
Marker Leiomyoma Leiomyosarcoma
Desmin; h-caldesmon; smooth
muscle actin
histone deacetylase 8 (HDCA8)
Positive; h- caldesmon- m.spec
Epithelioid variant: -ve or focally
reactive
usually express; epithelioid and
myxoid leiomyosarcomas may show
lesser degrees of immunoreaction
oxytocin receptor, estrogen receptor
(ER), progesterone receptor(PR), and
WT1
Often positive; Oxytocin receptor
helps to distinguish a smooth muscle
tumor (positive) from an endometrial
stromal tumor (negative)
ER, PR, and AR in 30-40% of cases
CD10,9 cytokeratins and EMA CD10 in 40% of cellular leiomyomas often immunoreactive(EMA most
frequently positive in the epithelioid
variant)
P16; p53; Ki67 Ki67 lower; no overexpression p53&
p16 except LBN
Ki67 higher; overexpression of
p53(25-47%) and p16

48. Mixed epithelial and mesenchymal tumors
 Adenomyoma
 Atypical polypoid adenomyoma
 Adenofibroma
 Adenosarcoma
 Carcinosarcoma

49. Mixed epithelial and mesenchymal tumors
Atypical polypoid adenomyoma. Shown is
an admixture of fibromyomatous stroma with
endometrial-type glands
Adenosarcoma. Note the phyllodes-like glandular growth
pattern, with prominent hypercellular stroma cuffing the glands.
HP: stromal cellular atypia

50. Mixed epithelial and mesenchymal tumors
Carcinosarcoma. Note the sharply demarcated
sarcomatous
region with malignant cartilage (bottom) contrasting
with the

51. THANKYOU

52. REFFERANCES
 2014 WHO Tumors of the female genital tract
 Blaustein’s Pathology pf the female genital tract; 7th edition
 Problematic areas and new developments in uterine mesenchymal tumors; Nafisa Wilkinson &
Nicholas R Griffin; diag histopath; 2017
 Diagnostic use of immunohistochemistry in uterine mesenchymal tumors; Emanuela et al;
seminars in diag path; 2014
 Recent developments in uterine mesenchymal neoplasms; Sarah Chiang & Esther Oliva; histopath;
2013

53. REFFERANCES
 Uterine mesenchymal tumors; Nikhil A. Sangle, Subodh M. Lele1; IJPM; 2011
 Malignant mesenchymal tumors of the uterus - time to advocate a genetic classification;
Birgit et al; Expert Review of Anticancer Therapy; 2016