Epithelial tumors
Perivascular epithelioid cell tumor (PEComa)

Author: Mohamed Mokhtar Desouki, M.D., Ph.D. (see Authors page)

Revised: 3 February 2017, last major update August 2011

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed search: perivascular epithelioid cell tumor uterus, PEComa uterus

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Cite this page: Uterus - Perivascular epithelioid cell tumor (PEComa). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/uterusPEComa.html. Accessed January 21st, 2019.
Definition / general
  • Poorly defined, rare tumors characterized by varying amounts of epithelioid and spindle cells with clear to eosinophilic, granular cytoplasm that is HMB45+ in a diffuse or focal pattern
  • Tumors are morphologically and immunophenotypically similar to the perivascular epithelioid cells of epithelioid angiomyolipoma, clear cell ("sugar") tumor, clear cell myomelanocytic tumor of ligamentum teres / falciform ligament and abdominopelvic sarcoma of perivascular epithelioid cells, and a subset of the cells in some examples of lymphangioleiomyomatosis (see Soft tissue tumor chapter)
  • Only PEComas of the uterine corpus were recognized in the 2003 WHO classication of gynecologic neoplasms
  • Mean age of 45 years (range, 9 - 79 years)
  • ~50 cases reported in English language literature
  • Uterus and retroperitoneum
  • Etiology unknown; tumors may be associated with tuberous sclerosis complex (~9% of cases reported)
Clinical features
  • Abnormal uterine bleeding, uterine mass, abdominal pain, hemoperitoneum or hydrosalpinx
  • Considered a tumor of uncertain malignant potential (Am J Surg Pathol 2002;26:1)
  • May exhibit aggressive behavior and recur after hysterectomy
  • Hysterectomy, with or without adjuvant chemotherapy and radiotherapy
Gross description
  • Solitary or rarely multifocal mass in uterine corpus from 0.6 to 12.0 cm (mean of 4.7 cm)
  • Cut sections may be grayish white, tan or yellow with whorled or soft, fleshy, ill defined or rarely circumscribed margins
Gross images

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Polypoid mass

Microscopic (histologic) description
  • Tumors divided into two groups (A and B), each of which is either benign or malignant
  • Group A demonstrates a tongue-like growth pattern similar to low grade endometrial stromal sarcoma; cells are epithelioid, medium sized with round / oval nuclei, well defined cell borders, abundant granular or clear to eosinophilic cytoplasm, with or without spindle cells; rarely small nests are separated by hyalinized stroma
  • Usually no / mild pleomorphism; may have slightly enlarged nuclei with small nucleoli, but relatively smooth nuclear membranes, and evenly dispersed chromatin; may have intranuclear pseudoinclusions
  • Variable large, thick walled vessels
  • No mitotic figures, no tumor cell necrosis
  • Strong, diffuse cytoplasmic HMB45 expression and focal muscle marker expression
  • Group B tumors are composed mainly of diffuse sheets of cells, separately by occasional small, hyalinized bundles and plaques of stroma; contain primarily perivascular epithelioid cells (> 50% are round or polygonal) with less prominent, clear features, focal HMB45 expression, and strong, extensive muscle marker expression
  • Possibly malignant features include mitotic activity > 1/10 HPF, necrosis, tumor size > 5 cm, infiltrative growth pattern, high nuclear grade, cytologic atypia, high cellularity, lymphovascular invasion, infiltration (Adv Anat Pathol 2008;15:63)
Microscopic (histologic) images

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Tumors of cervix and endometrium

Positive stains
Negative stains
Electron microscopy description
  • Cytoplasmic myelin figures and marginated nuclear chromatin; no melanosomes
Differential diagnosis