Uterus
Epithelial tumors
Perivascular epithelioid cell tumor (PEComa)

Editor-in-Chief: Debra Zynger, M.D.
Jennifer Bennett, M.D.

Topic Completed: 25 February 2019

Revised: 26 February 2019

Copyright: 2002-2019, PathologyOutlines.com, Inc.

PubMed Search: PEComa uterus[title]

Jennifer Bennett, M.D.
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Cite this page: Bennett J. Perivascular epithelioid cell tumor (PEComa). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/uterusPEComa.html. Accessed September 18th, 2019.
Definition / general
  • Rare mesenchymal neoplasm with myomelanocytic differentiation favored to arise from perivascular epithelioid cells
Essential features
  • Best classified as a tumor of uncertain malignant potential as recurrences may occur years after initial diagnosis
  • Characterized by clear to eosinophilic epithelioid or spindled cells growing in sheets, nests or cords and surrounded by delicate vasculature
  • Expresses both melanoma and smooth muscle markers with variable staining intensity and distribution
  • Only ~10% are associated with tuberous sclerosis complex
Terminology
  • Perivascular epithelioid cell tumor (PEComa)
  • Abdominopelvic sarcoma of perivascular epithelioid cells
  • Primary extrapulmonary sugar tumor (PEST)
ICD-0
  • 8000/1: neoplasm, uncertain whether benign or malignant
  • 8000/3: neoplasm, malignant
ICD-10
  • D39.0: neoplasm of uncertain behavior of uterus
  • C54.9: malignant neoplasm of corpus uteri, unspecified
Epidemiology
  • Only ~100 cases reported to date
  • Most commonly present at 40 - 60 years (range: 9 - 80)
Sites
  • Uterine corpus most common in gynecologic tract
    • Rarely cervix, vagina, ovary, broad ligament
Pathophysiology
  • Unknown
Etiology
  • ~10% associated with tuberous sclerosis complex
Clinical features
  • Generally present with nonspecific gynecologic symptoms (abnormal uterine bleeding, abdominal / pelvic pain) (Am J Surg Pathol 2018;42:1370)
  • May be incidentally discovered during evaluation for adnexal mass, leiomyomas, infertility or at cesarean section
Radiology description
  • No defining features to distinguish from other uterine mesenchymal neoplasms on imaging
Radiology images

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Sagittal T2 with heterogeneous hyperintense mass (arrows)

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MRI with hyperintense mass

Prognostic factors
  • 3 algorithms have been proposed for predicting behavior
    • Nongynecologic specific criteria (Am J Surg Pathol 2005;29:1558)
      • Benign: < 5 cm, non infiltrative, non high grade atypia, mitoses ≤ 1 / 50 high powered fields (HPFs), no necrosis, no lymphovascular invasion (LVI)
      • Uncertain malignant potential: nuclear pleomorphism / multinucleated giant cells or > 5 cm
      • Malignant: 2+ features (> 5 cm, non infiltrative, 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 (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
  • Variable and resembles other mesenchymal lesions (Am J Surg Pathol 2018;42:1370)
  • Typically intramural but may be polypoid
  • Tan, white or gray solid mass, variable hemorrhage or necrosis
Gross images

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Posterior uterine mass

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PEComa

Microscopic (histologic) description
Microscopic (histologic) images
Contributed by Jennifer Bennett, M.D.
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PEComa

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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 / MART-1

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Desmin

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Cathepsin K

Virtual slides

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Uterine mass

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Irregular nesting of epithelioid cells

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Mitotically uniform nuclei with central nucleoli

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Epithelioid cells with granular cytoplasm

Positive stains
Negative stains
Electron microscopy description
  • May see premelanosomes and melanosomes
Differential diagnosis
Board review 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. HTR4-ST3GAL1 fusion
  2. RAD51B fusion
  3. TFE3 fusion
  4. TFEB fusion
  5. TSC2 mutation
Board review answer #1
E. TSC2 mutation

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Board review question #2
    A 50 year old woman presents with a myometrial mass with lung metastases. The myometrial tumor is characterized by dyshesive 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. Melanoma
  4. PEComa
  5. Poorly differentiated endometrial carcinoma
Board review answer #2
D. PEComa

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