DW imaging with b values of 0 and 800 sec/mm(2) allows sensitive and specific differentiation of clear cell, papillary, and chromophobic RCCs, suggesting that DW imaging may be useful in the preoperative characterization of RCC.

Malignant peripheral nerve sheath tumors (MPNST) represent a group of highly heterogeneous human malignancies often with multiple histological origins, divergent differentiation patterns, and diverse immunohistochemical presentations. The differential diagnosis of MPNST from other spindle cell neoplasms poses great challenges for pathologists. This report provides a mini-review of these unique features associated with MPNST and also presents the first cases of MPNST with six differentiation patterns.

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Primary choriocarcinomas of the liver are rare. Previous reported cases were mostly in infants with only rare adult cases. Here, we presented five adult cases. The patients were all males, with an average age of 41.6 years (from 36 to 48 years). Clinical presentations included right upper abdominal pain or abdominal distension. All patients presented with a large hepatic mass on ultrasonography that measured 11 cm on average in the greatest diameter. Elevated serum human chorionic gonadotropin (HCG) levels were noted in all cases. At presentation, the tumor was confined to the liver in two patients and therefore surgically resected. The other three patients presented with extrahepatic metastases on imaging study and therefore only received chemotherapy. All five patients died from the tumor within 2 to 8 months. Autopsy was performed for all five cases. The autopsy confirmed that the choriocarcinoma was confined to the liver in two surgically resected cases. The other three patients had metastatic choriocarcinoma in the lung (two patients), peritoneum (one patient), adrenal glands (one patient), and brain (one patient). None of the patients had any evidence of a testicular tumor or scar after examination of the entirely submitted testes. No tumor was observed in central nervous system, mediastinum, or other organs other than described above. Grossly, the primary tumors were large, soft, hemorrhagic, and with foci of necrosis. Histologically, the tumors were composed of mononucleated trophoblastic cells with round nuclei, clear cytoplasm, and prominent nucleoli admixed with large, multinucleated syncytiotrophoblastic cells. Immunohistochemically, tumor cells were strongly positive for keratin, HCG, and focally positive for human placental lactogen. Ki-67 proliferation index was high (mean 75%) in the mononucleated trophoblastic cells. Our series is the largest one to document primary hepatic choriocarcinoma in adults. Although these tumors are rare, they behave in a very aggressive fashion.

This study describes the clinical, histologic, and immunohistochemical features of four cases of GI PEComa. The size of the tumors ranged from 3.5 to 6.0cm in diameter, and all were located in wall of the large bowel. Microscopically, the tumors were characterized by an epithelioid arrangement of tumor cells, which had abundant clear to pale eosinophilic granular cytoplasm, vesicular nuclei and prominent nucleoli. The stroma was rich in capillaries, a sinusoidal vasculature and thick-walled blood vessels. Mitotic figures were generally rare. Immunohistochemically, the tumors were positive for Vimentin (4/4), HMB-45 (4/4), Melan-A(4/4),alpha-smooth muscle actin (4/4), and desmin (3/4). The patients have been well with no evidence of disease at 8, 15, 32 and 36 months,respectively, after the surgical operation. GI tract PEComas should be regarded as tumors of an uncertain malignant potential until long-term outcome data for a larger number of patients become available.