Malignant PEComa: a case report with emphasis on clinical and morphological criteria

Abstract

Background: Malignant perivascular epitheliod cell tumor (PEComa) is a very rare entity composed of distinctive perivascular epitheliod cells with variable immunoreactivity for melanocytic and muscle markers. At present this neoplasm does not have a known normal cellular counterpart and the natural history is often unpredictable. Up to now, few cases of PEComa have been described and treatment modalities are still controversial, particularly in advanced conditions.

Case presentation: We handled the case of a 42-year-old man with unresectable PEComa of the abdomen. A 7 cm hepatic hypodense lesion between segment V and VIII of the liver and diffuse intraperitoneal nodules of 0,3-3,5 cm along the right subcapsular hepatic region, were documented by a CT scan. Radiological images showed abnormal lymph nodes of the right internal mammary chain and anterior mediastinum. The patient underwent an explorative laparotomy for uncontrolled intraabdominal hemorrhage without a well-defined preoperative tumor diagnosis. At surgery, multiple lobulated nodules containing hemorrhagic fluid on the liver surface, peritoneum and omentum were confirmed. The procedure had a palliative intent and consisted of hemostasis, hematomas evacuation and omentectomy. The diagnosis of PEComa was made after surgery on the basis of morphological and immunohistochemical criteria. Radiological and intra operative findings suggest that the mass has an hepatic origin with diffuse involvement of hepatic capsule and suspensory ligaments. The patient received medical support care with blood and plasma transfusions. In our experience, PEComa was clinically malignant, leading to a fatal outcome 25 days after hospital admission of patient.

Conclusions: Here we report and discuss the peculiar clinical, radiological and morphological presentation of unresectable PEComa. Although in the majority of the reported series, PEComas show a more better prognosis, our case presents with a particular aggressive biological behaviour. The importance of a correct preoperative diagnosis, the need for more effective targeted therapies based on tumor molecular knowledge and evidence-based clinical studies are emphasized together with a revision of the concerning scientific literature.

Figure 1

CT appearance of PEComa: axial (a), coronal (b) and sagittal (c) reconstructions. CT of the abdomen showed a 7 cm lesion in the right lobe of the liver with multiple ovular lesions of 0.5-3.5 cm along right triangular ligament, hypoattenuating relative to the surrounding hepatic tissue with minute calcifications. Hypodense lesions along right triangular ligament and capsular profile of falciform ligament were additionally documented. In the thorax CT images, abnormal lymph nodes of 2,8 cm in length were observed along internal right mammary chain, anterior mediastinum and aorta-lung interface. Multiple nodular lesions of the lung were documented in the right hemi-thorax.

Figure 2

Intraoperative appearance of PEComa. Multiple lobulated nodules containing hemorrhagic fluid on the hepatic capsule, peritoneum surface (a) and omentum (b) associated with hemoperitoneum were observed. The surgical procedure consisted in toilette of peritoneal cavity, omentectomy and hemostasis. In our case, it was impossible to perform an oncological curative surgery.

Figure 3

Histological and immunohistochemical profile of PECs. Tumor cells showed severe atypia, cytological pleomorphism, high mitotic activity and atypical mitotic figures (Hematoxylin-Eosin, x40)(a). Both epithelioid and spindle cells were diffusely positive for HMB-45 (x200)(b) and Melan-A (x63)(c) antigens in the cytoplasm. The prominent capillary network, but not tumor cells, showed CD34 positive staining (x40)(d).

Figure 4

Histological and immunohistochemical profile of PECs. Tumor cells showed marked coagulative necrosis (Hematoxylin-Eosin, x40) (a). In PECs, SMA had a focally cytoplasmic positivity (x40)(b). Nuclear MIB-1 reactivity was documented in PECs (x200)(c). We observed a strong and diffuse membrane reactivity for CD31 in tumor cells (x40)(d). The tumor was negative for all other markers mentioned, including S-100, CKAE1/AE3, CK5, CD30.