Perivascular epithelioid cell
lesion (PEComas)
Vikram Prabhakar (DCP,DNB Pathology)

• PEComas are a collection of rare tumors defined
as “mesenchymal tumors composed of
histologically and immunohistochemically
distinctive perivascular epithelioid cells” .
• In 1991, Pea et al. described the presence of a
unique cell with “prominent cytoplasmic borders
and clear to granular, eosinophilic cytoplasm” in a
perivascular distribution in both angiomyolipoma
(AML) of the kidney and clear cell sugar tumor
(CCST) of the lung .

• PEComas are related to the genetic alterations of
tuberous sclerosis complex (TSC), an autosomal
dominant genetic disease due to losses of TSC1
(9q34) or TSC2 (16p13.3) genes which have a role
in the regulation of the Rheb/mTOR/p70S6K
pathway.
• PEComas can occur at the extremes of age, but
the median age of 43 years in
• A strong female predominance has been seen ;
approximately 4 : 1

PEComa-NOS have been described in a variety of anatomic
locations, including:--
1. the colon
2. pancreas
3. retroperitoneum
4. heart
5. adrenal gland
6. breast
7. eye
8. biliary tract
9. bone
10. urinary bladder
11. skull base
12. liver
13. uterus cervix
14. skin
15. nasopharynx
16. upper airway
17. soft tissues

• PEComs has been given a variety of titles,
including:--
1. clear cell sugar tumor
2. primary extrapulmonary sugar tumor
3. clear cell myomelanocytic tumor
4. monotypic epithelioid angiomyolipoma

What is the perivascular epithelioid cell?
• It has morphologic, epithelioid appearance
with a clear to granular cytoplasm, a round to
oval, centrally located nucleus and an
inconspicuous nucleolus. PEC has mild to any
atypia and a typical perivascular location .
• At present, PEC has not a known normal
counterpart.

Immunohistochemically
• PEComas express myogenic and melanocytic
markers, such as HMB45, HMSA-1,
MelanA/Mart1, microophtalmia transcription
factor (Mitf), actin and, less commonly,
desmin .
• Its immunoreactivity for vimentin is usually
incospicuous.

ultrastructural analysis
• PEC contains microfilament bundles with
electron-dense condensation, numerous
mithochondria and membrane-bound dense
granules.

Different modulations

Kidney
• PEComas of the kidney include :--
1. classic AML
2. microscopic AML (so-called microhamartoma)
3. intraglomerular lesions
4. cystic AML,
5. epithelioid AML,
6. oncocytoma-like AML
7. lymphangiomyomatosis of the renal sinus.

Classic angiomyolipoma
• is the most common mesenchymal tumor of
the kidney.
• composed of a variable mixture of adipose
tissue and spindle and epithelioid smooth
muscle cells mixed together with abnormal
thick-walled blood vessels.

Renal angiomyolipoma: perivascular epithelioid cells arranged around a blood
vessel

Renal microhamartoma completely composed of perivascular
epithelioid cells

Lung
• PEComas of the lung include :--
1. Lymphangioleiomyomatosis
2. clear-cell “sugar” tumor.

Lymphangioleiomyomatosis
• It is a rare and progressive disease that affects
women, usually in premenopausal age;
occasionally
• Nodular, often widespread and bilateral
interstitial proliferation of HMB45, actin and
desmin-positive smooth muscle cells which can
vary from small spindle-shaped cells to large
epithelioid cells
• usually arranged around thin-walled, branching
vascular channels; which is associated with
dilated lymphatics and cystic changes

Pulmonary lymphangioleiomyomatosis composed of epithelioid cells
arranged around a vascular channel

Clear cell sugar tumor
• It was originally described in the lung
• Rare and benign neoplasm composed of a
uniform population of round-to-polygonal
epithelioid cells, with a clear or eosinophilic
cytoplasm and well-defined cell borders.
• Tumor cells are surrounded by prominent and
thin-walled vascular channels, having a
nested or alveolar .

Pulmonary clear-cell “sugar” tumor composed of epithelioid cells
with a clear cytoplasm and well-defined cell borders. With
prominent and vascular channel is present

Pulmonary clear-cell “sugar” tumor: HMB45 immunoreactivity in
tumor cells

Liver
Hepatic angiomyolipoma: solid component made of large epithelioid cells

The tumor cells are strongly and diffusely immunoreactive for HMB45
(A), Melan A (B), and vimentin (C) and focally immunoreactive for α-
smooth muscle actin (SMA)

Pancreas
Pancreatic clear-cell “sugar” tumor: epithelioid cells, with a clear
cytoplasm and with a nested or appearance

Uterus
Uterine PEComa composed of epithelioid cells with a clear cytoplasm
and well-defined cell borders

Bladder
Bladder PEComa composed of epithelioid cells with clear cytoplasm
arranged in nests

Prostate
Prostatic PEComa composed of epithelioid cells with clear cytoplasm
arranged in nests

Differential diagnosis
1. Clear cell / oxyphilic carcinoma: cytokeratin+
2. Epithelioid / clear cell smooth muscle
tumors: HMB45-
3. Melanoma: strong S100+
4. Undifferentiated / high grade sarcoma

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