Uterus

Other mesenchymal tumors

Perivascular epithelioid cell tumor (PEComa)


Editorial Board Member: Stephanie L. Skala, M.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Jennifer A. Bennett, M.D.

Last author update: 23 May 2022
Last staff update: 23 May 2022

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PubMed Search: PEComa uterus

Jennifer A. Bennett, M.D.
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Cite this page: Bennett J. Perivascular epithelioid cell tumor (PEComa). PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/uterusPEComa.html. Accessed July 5th, 2022.
Definition / general
  • Rare mesenchymal neoplasm with myomelanocytic differentiation that is favored to arise from perivascular epithelioid cells
Essential features
  • Best classified as a tumor of uncertain malignant potential since recurrences may arise years after initial diagnosis
  • Characterized by sheets or nests of epithelioid cells with clear to eosinophilic and granular cytoplasm, surrounded by delicate vasculature
  • Coexpresses melanoma and smooth muscle markers, with variable staining intensity and distribution
  • 2 main molecular subgroups: TSC1 / TSC2 alterations, TFE3 fusions
ICD coding
  • ICD-10:
    • D39.0 - neoplasm of uncertain behavior of uterus
    • C54.9 - malignant neoplasm of corpus uteri, unspecified
  • ICD-11
    • 2F76 - neoplasms of uncertain behaviour of female genital organs
    • 2C76.Z - malignant neoplasms of corpus uteri, unspecified
Epidemiology
Sites
  • Uterine corpus is most common in gynecologic tract
  • Rare in cervix, vagina, ovary, broad ligament and vulva
Pathophysiology
Etiology
Clinical features
Diagnosis
  • Rarely made on endometrial sampling
  • Myomectomy or hysterectomy
Radiology description
  • No defining features to distinguish from other uterine mesenchymal neoplasms on imaging
Radiology images

Images hosted on other servers:
Sagittal T2 with heterogeneous hyperintense mass (arrows)

Sagittal T2 with heterogeneous hyperintense mass

MRI with hyperintense mass

MRI with hyperintense mass

Prognostic factors
  • 3 main algorithms have been proposed for predicting behavior
    • Nongynecologic specific criteria (Am J Surg Pathol 2005;29:1558):
      • Benign: < 5 cm, noninfiltrative, no high grade atypia, mitoses ≤ 1/50 high power fields (HPFs), no necrosis, no lymphovascular invasion (LVI)
      • Uncertain malignant potential: nuclear pleomorphism / multinucleated giant cells or > 5 cm
      • Malignant: 2+ features (> 5 cm, noninfiltrative, high grade atypia, mitoses > 1/50 HPFs, necrosis, LVI)
    • Gynecologic specific criteria (Am J Surg Pathol 2014;38:176):
      • Benign / uncertain malignant potential: < 4 features (≥ 5 cm, high grade atypia, mitoses > 1/50 HPFs, necrosis, LVI)
      • Malignant: ≥ 4 features
    • Modified gynecologic specific criteria (adopted by the WHO 2020) (Am J Surg Pathol 2018;42:1370)
      • Uncertain malignant potential: < 3 features (> 5 cm, high grade atypia, mitoses > 1/50 HPFs, necrosis, LVI)
      • Malignant: ≥ 3 features
  • Recurrences can occur years after original diagnosis
Case reports
Treatment
Gross description
  • Mean: 6.5 cm; range: 0.2 - 25 cm (Genes Chromosomes Cancer 2021;60:168)
  • Typically intramural but may be polypoid
  • Tan, white, pink or gray solid mass
  • Subset show hemorrhage or necrosis
Gross images

Images hosted on other servers:
Posterior uterine mass

Posterior uterine mass

PEComa

PEComa

Microscopic (histologic) description
  • Well circumscribed or infiltrative growth
  • Numerous growth patterns, with sheets and nests being the most common
  • Noncohesive epithelioid cells with clear to eosinophilic granular cytoplasm
    • May have a component of spindled cells (usually minor)
    • Subset have dense eosinophilic (rhabdoid) or foamy cytoplasm
  • Variable cytologic atypia and mitotic index
  • Melanoma-like nucleoli, intranuclear pseudoinclusions, multinucleated cells, Touton giant cells and melanin pigment (rare) may be present
  • Characterized by thin and delicate vessels but may also have thick walled (generally peripherally located) and staghorn vessels
  • Radial / perivascular distribution of tumor cells identified in < 25% (Am J Surg Pathol 2018;42:1370)
  • Stromal hyalinization is common
  • TFE3 translocation associated PEComas (Am J Surg Pathol 2010;34:1395, Am J Surg Pathol 2015;39:394):
    • Typically epithelioid with clear cells in a nested / alveolar growth
    • Low grade atypia and rare mitoses
  • Lymphangioleiomyomatosis (LAM)-like PEComas are rare, predominantly spindled with thick walled blood vessels, cleft / slit-like spaces, low grade atypia and infrequent mitoses (Am J Surg Pathol 2018;42:1370)
Microscopic (histologic) images

Contributed by Jennifer Bennett, M.D.
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Diffuse growth of epithelioid cells

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Infiltrative growth

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Delicate vasculature

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Spindled cells


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Stromal hyalinization

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Multinucleated giant cells

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Intranuclear pseudoinclusions

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Melanoma-like macronucleoli

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TFE3 associated PEComa


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LAM-like PEComa

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HMB45

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MelanA / MART1

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Desmin

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Cathepsin K

Positive stains
Negative stains
Molecular / cytogenetics description
Sample pathology report
  • Uterus, hysterectomy:
    • PEComa of uncertain malignant potential (4.5 cm) (see comment)
    • Chronic cervicitis
    • Proliferative endometrium
    • Leiomyomas
    • Comment: 1 of the myometrial nodules is comprised of sheets of epithelioid cells with clear to eosinophilic and granular cytoplasm. Cytologic atypia, mitoses and necrosis are not appreciated. This nodule is positive for HMB45 (50%, strong), MelanA (focal), desmin, caldesmon and SMA. The morphologic and immunoprofile supports the diagnosis of PEComa. Based on the WHO 2020 criteria for predicting behavior in PEComas, this tumor would classify as being of uncertain malignant potential. Most tumors in this category have a benign clinical course; however, as a small subset recur, close clinicoradiological follow up is recommended.
Differential diagnosis
Board review style question #1
A 32 year old woman with a history of pulmonary lymphangioleiomyomatosis, seizures and angiofibromas presents with a myometrial mass. Which molecular / cytogenetic abnormality does this patient likely have?

  1. JAZF1-SUZ12 fusion
  2. RAD51B fusion
  3. TFE3 fusion
  4. TP53 mutation
  5. TSC2 mutation
Board review style answer #1
Board review style question #2

A 50 year old woman presents with a myometrial mass with lung metastases, as seen in the image. The myometrial tumor is characterized by noncohesive epithelioid and spindled cells surrounded by a delicate vasculature. The tumor cells are strongly and diffusely positive for HMB45, desmin, SMA and caldesmon with focal MelanA expression. What type of tumor does this likely represent?

  1. Alveolar soft part sarcoma
  2. Leiomyosarcoma
  3. Low grade endometrial stomal sarcoma
  4. Melanoma
  5. Perivascular epithelioid cell tumor (PEComa)
Board review style answer #2
E. Perivascular epithelioid cell tumor (PEComa)

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Reference: Perivascular epithelioid cell tumor (PEComa)
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