A 42-year-old male was admitted to our observation with dyspnea, temperature, abdominal discomfort and weight loss. He had previously experienced tuberculosis infection, and his past surgical history was uneventful. The physical examination confirmed epigastric and mesogastric pain. The radiological images demonstrated right fluid pleurical collection with passive collapse of the lung inferior lobe, abnormal lymph nodes of the right internal mammary chain and anterior mediastinum (Figure 1). At the patient admission, we had drained the right symptomatic hemothorax and sent to our pathologists the pleurical fluid for cytology exam. The patient underwent an abdominal CT scan that demonstrated a 7 cm hypodense lesion between segment V and VIII of the liver with minute calcifications, inhomogeneously hypoattenuating relative to the surrounding liver parenchyma. This lesion was surrounded by a very thin capsule showing irregular limits in the cranial portion. The right hepatic lobe showed irregular profile with the presence of diffuse lesions of 0,5-3,5 cm in length, reported along right triangular ligament and subcapsular hepatic region, suspected for hematomas. Hemoperitoneum was also documented (Figure 1). According to the severe clinical condition and the hemodynamic instability, the patient underwent hepatic angiography with selective catheterization of the common hepatic artery, its branches and right diaphragmatic artery. The diagnostic phase of angiography did not document any active bleeding, as well as during the selective coaxial study of the intrahepatic arterial branches of right hemi-system and right diaphragmatic artery. An exploratory laparotomy was finally proposed. At surgery, the hepatic mass, the multiple subcapsular hematomas, and the hemoperitoneum were confirmed (Figure 2). The liver had no signs of cirrhosis. The extemporaneous biopsy showed signs of undifferentiated carcinoma. The surgical procedure consisted in omentectomy, toilette and hemostasis of the peritoneal cavity.
The histological diagnosis of malignant PEComa is based on the published criteria by Folpe and co-workers. In our case, the tumor is characterized by the proliferation of epitheliod and spindle cells. The neoplastic cells are arranged in small-nests or sheet-like patterns, traversed by a delicate vasculature consisting of a rich network of sinusoid-type blood vessels. The tumor cells showed a round to oval nucleus, often with prominent nucleolus and exhibited high nuclear pleomorphism. The tumor is comprised of a population of large polyclonal cells with abundant cytoplasm. The mitotic index is elevated (> 40 figures per 50 high power fields, HPF) and the coagulative necrosis, a prominent feature, appeared as multiple foci of variable sizes. Microscopically the tumor border was infiltrative.
For immunohistochemistry on formalin-fixed paraffin-embedded samples, sections were treated with H2O2/3% for 5 minutes to inhibit endogenous peroxidase and then washed in H2O. Antigen was unmasked by treatment with EDTA at pH 9, or with citrate buffer at pH 6 in a microwave oven (two 5-minutes courses). The slices were then held for 20 minutes at room temperature. After washing in PBS/Tween-20, sections were incubated for 30 minutes with the primary antibodies. Then, they were washed and stained with Bond  Polymer Refine/HRP Detection Kit according to the manufacturer's protocol (Leica, Wetzlar, Germany) or Bond  Polymer Refine Red Detection Kit (Leica) for HMB-45 an Melan-A. For negative controls, we substituted non-immune sera for the primary antibodies. The immunohistochemistry analysis demonstrated positive staining for Vimentin (Novocastra), Melan-A (Dako), HMB-45 (Dako), smooth muscle actin (SMA) (Dako), MIB-1(Novocastra), and CD31 (Novocastra). It was negative for S-100 protein (Dako), Cytokeratin-AE1/AE3 (CKAE1/AE3) (Novocastra), Cytokeratin-5 (CK5) (Novocastra), CD30 (Dako). Based on this specific immunophenotype profile, diagnosis of PEComa was made (Figure 3-4). The multiple lesions, suspected to be lymphatic metastasis in the thorax CT images, were not confirmed by a cytology exam of pleurical fluid. Infact, the cytology analysis has documented the presence of leucocytes, red globular cells and rare mesothelial cells, but not tumor cells. It was impossible in our case to confirm histologically the suspected metastatic lesions observed along lymphatic internal right mammary chain, anterior mediastinum, aorta-lung interface and of the lung.
The immediate post-operative course was uneventful and the patient received supporting therapy with blood and plasma transfusions. PEComa was clinically malignant, leading to a fatal outcome in our experience.