Malignant hepatic perivascular epithelioid cell tumor (PEComa) – Case report and a brief review

Abstract

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal neoplasms which can arise from almost any location in the body. Diagnosing them pre-operatively is difficult as they mimic features of other hepatic neoplasms including hepatocellular carcinoma (HCC), fibrolamellar HCC, and focal nodular hyperplasia (FNH) among others. The unique feature of these tumors is the coexpression of muscle and melanocytic markers. These are identified immunohistochemically by the expression of Human Melanin Black-45 (HMB-45), Melan-A and Smooth Muscle Antigen (SMA) which are seen in the majority of tumors. The liver is uncommonly associated with a PEComa and the approach to a patient with hepatic PEComa is not well described. There is no consensus regarding the neo-adjuvant/adjuvant therapy in these patients. The natural history of this condition is not well documented making it an unpredictable disease. Here we have discussed a case and reviewed the literature concerning these rare tumors.

Hepatic perivascular epithelioid cell tumor

“…[2,9–11] Hormones may play a key role in the pathophysiology. However, The histogenesis and pathogenesis of perivascular epithelioid cells (PECs) are still uncertain because physiological counterpart of PECs have not been defined.…”

“…However, The histogenesis and pathogenesis of perivascular epithelioid cells (PECs) are still uncertain because physiological counterpart of PECs have not been defined. [2] There are some hypotheses relating to the origin of PEC. The first one is that the PEC may develop from undifferentiated neural crest cells which have the ability of co-expressing the phenotype of smooth muscles and melanocytes.…”

“…[2,29] In 2005, Folpe et al [30] reviewed 26 cases of gynecological origins and soft tissue, and proposed a classification of PEComas into benign, semimalignant, and malignant based on the 7 worrisome features of the histology: a tumor size >5 cm; infiltration into the surrounding normal tissue; high nuclear grade; high cellularity; motic activity of more than 1/50 per high power field; coagulative necrosis of the tumor; vascular invasion. The PEComa with 2 or more of the features that are listed should be considered to be malignant.…”

“…[2,3] In 2002, the World Health Organization defined PEComa as unusual mesenchymal tumors which compose of histologically and immunohistochemically distinctive perivascular epithelioid cells. [4] The PEComa tumor family includes classic epithelioid angiomyolipoma (AML), lymphangioleiomyomatosis, pulmonary and extrapulmonary clear-cell “sugar” tumors, and PEComa.…”

Hepatic angiomyolipoma: mutation analysis and immunohistochemical pitfalls in diagnosis

“…The seven high‐risk features in this study included size >5 cm, high nuclear grade, hypercellularity, mitotic rate of >1/50 high‐power field, necrosis, infiltration into surrounding normal parenchyma and vascular invasion. Most reported cases of malignant hepatic AML in the literature had at least two high‐risk features, with most being >5 cm and having necrosis, including one case in the current study. Additional high‐risk features such as marked nuclear atypia (three cases), high mitoses (two cases) and vascular invasion (two cases) were described in other reports of malignant hepatic AML .…”