Perivascular Epithelioid Cell Tumor (PEComa)

The symptoms associated with PEComas depend on the location where the tumor manifests and symptoms can be nonspecific, similar to other forms of cancer. The nonspecific symptoms requiring patients to seek medical attention include weight loss, pain or discomfort, abnormal bleeding or development of abnormal mass or masses. Small tumors may not present with any significant signs or symptoms specific to cancer.  Large tumors could compress the surrounding organs or structures causing pain and more specific symptoms relating to the specific location of involvement.

PEComas are often discovered by accident during radiologic imaging studies and can be classified as benign, uncertain malignant potential or malignant. Confirming a cancer diagnosis requires a biopsy of the tumor in question. A doctor will then analyze the characteristics of the cells that make up the tumor and subject the sample to a variety of lab tests. These laboratory studies are necessary to rule out other types of cancers such as gastrointestinal stromal tumors (GIST), leiomyosarcoma, melanoma metastases, carcinomas, smooth muscle tumors, other clear cell neoplasms and adipocytic tumors. There are genetic markers and cell markers that can help identify PEComa tumors as well. Ultimately, the factors to consider while diagnosing and determining malignancy include tumor size, increased cell abnormalities, infiltration to surrounding tissues and blood vessels, presence of necrosis and mitotic activity.

The primary treatment for PEComas includes radical resection and is typically curative. Radical resection is the surgical removal of the tumor as well as other areas the cancer may have spread to. PEComas are usually resistant to radiation and chemotherapy, so these treatments are generally avoided. Reports of overactivation in the mTOR “cell proliferation” pathway have been studied and significantly involved in advanced and malignant PEComas. In case studies, the drug class of mTOR inhibitors such as sirolimus, temsirolimus and everolimus have been found to provide symptomatic relief, decrease the size of tumors and metastasis associated with PEComas and provide manageable side effect profiles. Nab-sirolimus, FYARRO, is a novel mTOR inhibiting agent bound to human albumin and is administered through IV infusion as the first approved treatment for advanced PEComa. This new targeted delivery method has achieved rapid responses in responding patients in as little as 6 weeks of therapy and has shown higher tumor accumulation, greater mTOR suppression and greater tumor growth inhibition compared to other mTOR inhibitors in preclinical models.