PEComa

PEComa
Histopathologic image of renal angiomyolipoma. Nephrectomy specimen. H&E stain.
MeSH	D054973

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Zahir Ali Shaikh, MD[2]

Synonyms and keywords:

Overview

The World Health Organization defines Perivascular Epithelioid Cell Tumors (PEComas) as mesenchymal tumors composed of histologically and immunohistochemically distinctive perivascular epithelioid cells (PECs).

Historical Perspective

PEComas was first discovered by Pea and Colleagues in 1991, where they first noticed this unusual cell in both Angiolyolipoma (AML) and Clear Cell Sugar Tumor of Lung (CCST).

In 1992, Bonetti and Colleagues proposed a cellular link between AML, CCST and lymphangioleiomyomatosis (LAM), their association with Tuberous Sclerosis Complex (TSC) and advanced the concept of a family of neoplasms composed of these distinctive cells which were immunoreactive with melanocytes markers and exhibit and epitheloid appearance, a clear acidophilic cytoplasm and a perivascular distribution.

In 1996, Zamboni et al reported the first case of Pancreatic CCST and suggested the name PEComa for these neoplasms composed of a pure proliferation of Perivascular Epirhloid Cells (PECs).

Classification

The World Health Organization defines Perivascular Epithelioid Cell Tumors (PEComas) as mesenchymal tumors composed of histologically and immunohistochemically distinctive perivascular epithelioid cells (PECs)

There is no established system for the classification of PEComas because of the rarity of disease, but the PEComas are a group of tumors that includes following:

• Angiomyolipoma (AML)
• Clear Cell Sugar Tumor Of Lung (CCST)
• Lymphangileiomyomatosis (LAM)
• PEComas Not Otherwise Specified (PEComas-NOS); which includes Clear Cell Myomelanocytic Tumor of falciform ligament/ligamentum teres, Abdominopelvic Sarcoma of perivascular epethelioid cells, primary extrapulmonary clear cell sugar tumor.

Pathophysiology

Perivascular Epithlioid Cell (PEC) is a cell type constantly present in a group of tumors called PEComas. It has no normal counterpart.

PEC expresses myogenic and melanocytic markers such as HMB45 and Actin.

Microscopic Pathology

Perivascular Epithlioid Cells (PECs) are perivascular epithelioid cells with a clear/granular cytoplasm and round, oval, centrally located nucleus without prominent nucleoli. They have mild to any atypia.

On ultrastructural analysis PEC contains microfilament bundles with electron dense condensation, numerous mitochondria and membrane bound dense granules.

Genetics

The precursor cell of PEComas is currently unknown. Genetically, PECs are linked to the tuberous sclerosis genes TSC1 and TSC2.

Causes

PEComas are cause by genetic factors. Mutations in the tuberous sclerosis genes TSC1 and TSC2 has been associated.

Differentiating PEComa from other Diseases

PEComas must be differentiated from:

• Epithelioid Smooth Muscle cell tumors(epithelioid leiomyosarcoma and epithelioid leiomyoma),
• Malignant Melanoma,
• Clear cell sarcoma of tendon and aponeroses(melanoma of soft parts),
• Alveolar soft part sarcoma,
• Endometrial stromal sarcoma with clear cell features,
• Carcinoma (especially renal cell and adrenocortical carcinoma)
• Paraganglioma
• Any other tumor with focal or prominent clear cell change

Epidemiology and Demographics

Patients of all age groups may develop PEComas, but the mean age at diagnosis is 54 years.

Women are more commonly affected by PEComas than men.

Risk Factors

There are no established risk factors for PEComas, but the risk increases in patients with Tuberous Sclerosis as the PECs are associated with TSC1 and TSC2 genes.

Screening

There is insufficient evidence to recommend routine screening for PEComas.

Natural History, Complications, and Prognosis

• Clinically most PEComas follow a benign course.

• Malignant PEComas-NOS are also reported and seen in uterus. Other sites including jejunum, prostate, pelvis, skull base, somatic soft tissue and broad ligament.
• Folpe and Colleagues suggested criteria for malignancy based of following 03 factors:
  • Size greater than 8.0 cm
  • Mitotic count of 1/50 high power field (HPF)
  • Necrosis
    • They are categorized as Benign, Uncertain malignant potential and Malignant on the presence of none, 1, or 2 or more of the above three criteria.

Diagnosis

Immunohistochemical markers

PECs typically stain for melanocytic markers (HMB-45, HMSA-1, Melan A (Mart 1), microophthalmia transcription factor (Mitf)), myogenic markers (actin)and less commonly desmin. Immunoreactivity for vimentin is unclear.

Diagnostic Study of Choice

The diagnosis of [disease name] is made when at least [number] of the following [number] diagnostic criteria are met: [criterion 1], [criterion 2], [criterion 3], and [criterion 4].

OR

The diagnosis of [disease name] is based on the [criteria name] criteria, which include [criterion 1], [criterion 2], and [criterion 3].

OR

The diagnosis of [disease name] is based on the [definition name] definition, which includes [criterion 1], [criterion 2], and [criterion 3].

OR

There are no established criteria for the diagnosis of [disease name].

History and Symptoms

The majority of patients with [disease name] are asymptomatic.

OR

The hallmark of [disease name] is [finding]. A positive history of [finding 1] and [finding 2] is suggestive of [disease name]. The most common symptoms of [disease name] include [symptom 1], [symptom 2], and [symptom 3]. Common symptoms of [disease] include [symptom 1], [symptom 2], and [symptom 3]. Less common symptoms of [disease name] include [symptom 1], [symptom 2], and [symptom 3].

Physical Examination

Patients with [disease name] usually appear [general appearance]. Physical examination of patients with [disease name] is usually remarkable for [finding 1], [finding 2], and [finding 3].

OR

Common physical examination findings of [disease name] include [finding 1], [finding 2], and [finding 3].

OR

The presence of [finding(s)] on physical examination is diagnostic of [disease name].

OR

The presence of [finding(s)] on physical examination is highly suggestive of [disease name].

Laboratory Findings

There are no diagnostic laboratory findings associated with PEComas.

Electrocardiogram

There are no ECG findings associated with PEComas.

X-ray

There are no x-ray findings associated with PEDComas.

Echocardiography or Ultrasound

There are no echocardiography/ultrasound findings associated with PEComas.

CT scan

There are no CT scan findings associated with [disease name].

OR

[Location] CT scan may be helpful in the diagnosis of [disease name]. Findings on CT scan suggestive of/diagnostic of [disease name] include [finding 1], [finding 2], and [finding 3].

OR

There are no CT scan findings associated with [disease name]. However, a CT scan may be helpful in the diagnosis of complications of [disease name], which include [complication 1], [complication 2], and [complication 3].

MRI

There are no MRI findings associated with [disease name].

OR

[Location] MRI may be helpful in the diagnosis of [disease name]. Findings on MRI suggestive of/diagnostic of [disease name] include [finding 1], [finding 2], and [finding 3].

OR

There are no MRI findings associated with [disease name]. However, a MRI may be helpful in the diagnosis of complications of [disease name], which include [complication 1], [complication 2], and [complication 3].

Other Imaging Findings

There are no other imaging findings associated with [disease name].

OR

[Imaging modality] may be helpful in the diagnosis of [disease name]. Findings on an [imaging modality] suggestive of/diagnostic of [disease name] include [finding 1], [finding 2], and [finding 3].

Other Diagnostic Studies

There are no other diagnostic studies associated with PEComas.

Treatment

Medical Therapy

There is no treatment for [disease name]; the mainstay of therapy is supportive care.

OR

Supportive therapy for [disease name] includes [therapy 1], [therapy 2], and [therapy 3].

OR

The majority of cases of [disease name] are self-limited and require only supportive care.

OR

[Disease name] is a medical emergency and requires prompt treatment.

OR

The mainstay of treatment for [disease name] is [therapy].

OR   The optimal therapy for [malignancy name] depends on the stage at diagnosis.

OR

[Therapy] is recommended among all patients who develop [disease name].

OR

Pharmacologic medical therapy is recommended among patients with [disease subclass 1], [disease subclass 2], and [disease subclass 3].

OR

Pharmacologic medical therapies for [disease name] include (either) [therapy 1], [therapy 2], and/or [therapy 3].

OR

Empiric therapy for [disease name] depends on [disease factor 1] and [disease factor 2].

OR

Patients with [disease subclass 1] are treated with [therapy 1], whereas patients with [disease subclass 2] are treated with [therapy 2].

Surgery

Surgical intervention is not recommended for the management of [disease name].

OR

Surgery is not the first-line treatment option for patients with [disease name]. Surgery is usually reserved for patients with either [indication 1], [indication 2], and [indication 3]

OR

The mainstay of treatment for [disease name] is medical therapy. Surgery is usually reserved for patients with either [indication 1], [indication 2], and/or [indication 3].

OR

The feasibility of surgery depends on the stage of [malignancy] at diagnosis.

OR

Surgery is the mainstay of treatment for [disease or malignancy].

Primary Prevention

There are no established measures for the primary prevention of PEComas.

Secondary Prevention

There are no established measures for the secondary prevention of [disease name].

OR

Effective measures for the secondary prevention of [disease name] include [strategy 1], [strategy 2], and [strategy 3].

References

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