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Table of Contents
Definition / general | Epidemiology | Sites | Etiology | Clinical features | Treatment | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Positive stains | Negative stains | Electron microscopy description | Differential diagnosis | Additional referencesCite this page: Uterus - Perivascular epithelioid cell tumor (PEComa). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/uterusPEComa.html. Accessed July 16th, 2017.
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
Epidemiology
- Mean age of 45 years (range, 9 - 79 years)
- ~50 cases reported in English language literature
Sites
- Uterus and retroperitoneum
Etiology
- 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
Treatment
- 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
Images hosted on other servers:
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
- HMB45, SMA (73%), p53 (50%), melanA / MART1 (24% - 67%)
- Also calponin, vimentin, h-caldesmon; PR (50%), desmin (49%), muscle specific actin (36%), ER (33%), CD10 (25%)
Negative stains
- Chromogranin, p16, EMA, myosin, inhibin, CD56, cytokeratin (positive in 3%), S100 (positive in 3%), CD34 (positive in 5%), CD117 (positive in 9%), and synaptophysin (positive in 17%)
Electron microscopy description
- Cytoplasmic myelin figures and marginated nuclear chromatin; no melanosomes
Differential diagnosis
Additional references
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