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Objective: To study the immunohistochemical expression of S100A1, GLUT-1 and Cavolin-1 and its diagnostic significance in renal tumors with oncocytic features., Methods: Tissue microarray and immunohistochemical staining for S100A1, GLUT-1 and Cavolin-1 were carried out in 59 cases of renal tumors with oncocytic features, including 19 cases of renal oncocytoma, 15 cases of clear cell renal cell carcinoma (CCRCC) with eosinophilic cells, 11 cases of eosinophilic variant of chromophobe renal cell carcinoma, 7 cases of oncocytic papillary renal cell carcinoma and 7 cases of epithelioid angiomyolipoma., Results: S100A1 was expressed in renal oncocytoma, with a positive propotion of 16/19 (including 14 cases showing widespread and strong positivity). On the other hand, the rate of expression of S100A1 was 2/11 in eosinophilic variant of chromophobe renal cell carcinoma, 10/15 in CCRCC with eosinophilic cells, 3/7 in oncocytic papillary renal cell carcinoma and 6/7 in epithelioid angiomyolipoma (P>0.05). The difference of S100A1 expression between renal oncocytoma and eosinophilic variant of chromophobe renal cell carcinoma was statistically significant. GLUT-1 was located in cell membrane, with a positive rate of 13/15 in CCRCC with eosinophilic cells, 7/19 in renal oncocytoma, 4/7 (weak) in oncocytic papillary renal cell carcinoma, 1/11 in eosinophilic variant of chromophobe renal cell carcinoma and 0/7 in epithelioid angiomyolipoma. The rate of expression of Cav-1 was 6/15 in CCRCC with eosinophilic cells, 2/7 in oncocytic papillary renal cell carcinoma, 5/7 in epithelioid angiomyolipoma, 2/11 (weak) in eosinophilic variant of chromophobe renal cell carcinoma and 0/19 in renal oncocytoma. S100A1 showed high sensitivity and 50% specificity in the diagnosis of renal oncocytoma. GLUT-1 and Cav-1 showed high specificity and sensitivity in the diagnosis of CCRCC and epithelioid angiomyolipoma., Conclusions: S100A1 is widely expressed in various oncocytic renal neoplasms and helpful in differential diagnosis of renal oncocytoma from eosinophilic variant of chromophobe renal cell carcinoma, but not from other 3 oncocytic renal tumors. Overexpression of GLUT-1 can be used in distinction between CCRCC and renal oncocytoma. Cav-1 is widely expressed in CCRCC and epithelioid angiomyolipoma but not in renal oncocytoma. Cav-1 expression thus rules out renal oncocytoma.

Objective: To study the clinicopathologic features, immunophenotype, histological diagnosis and prognosis of hepatic epithelioid angiomyolipoma., Methods: Clinical data of 25 cases of hepatic epithelioid angiomyolipoma were collected along with follow-up study of the patients. The pathological features were documented and immunohistochemical study of various markers was performed with an emphasis on diagnosis and differential diagnosis., Results: Hepatic epithelioid angiomyolipoma was more commonly found in young women without characteristic clinical symptoms. Its morphological features were characterized by marked cytological atypia, relatively rare mitotic figures; radial distribution of tumor cells around the thin-walled blood vessels or muscular vessels; and the presence of common multinucleated giant cells and large ganglion-like tumor cells. The tumor cells expressed both melanoma cell markers (HMB45, MART-1) and smooth muscle cell markers (SMA). Tumor cells expressed various other markers including ER 16% (4/25), PR 32% (8/25), TFE3 24% (6/25) and p53 60% (15/25)., Conclusions: Hepatic epithelioid angiomyolipoma has variable morphological features and characteristic immunohistochemical phenotype. The differential diagnoses include a variety of tumors. The biological behavior of the tumor tends to be benign.

Objective: To investigate the clinicopathological characteristics of sporadic renal hemangioblastoma., Methods: Two cases of sporadic renal hemangioblastoma were studied by histological and immunohistochemical staining, along with review of the literature., Results: Both cases were presented with a renal mass during annual physical examination with an age of 40 and 45 years, respectively. The lesions located in the middle portion of the kidney with a sharp tumor border. Histopathologically, the tumors were characterized by two major components: capillary and stromal cells. Immunohistochemically, the stromal cells were positive for vimentin, NSE, S-100 protein and inhibin-α, and negative for CK, HMB45, Melan A, EMA, CD56 and syn. Both tumors showed a very low level of Ki-67 labeling. The endothelial cells were positive for CD34., Conclusion: Sporadic renal hemangioblastoma is a rare benign neoplasm, the diagnosis of which is based on the characteristic follicular architecture and an exclusion of other carcinomas of the kidney.

Objective: To study the clinicopathologic features, immunophenotype and genetic changes of perivascular epithelioid cell neoplasms (PEComa)., Methods: A total of 25 cases of PEComa located in various anatomic sites were selected for immunohistochemical staining (SP or EnVision method). TFE3 fluorescence in-situ hybridization was also performed to determine the TFE3 gene status., Results: The age of patient ranged from 21 to 61 years (mean = 43 years). The male-to-female ratio was 1: 1.3. Histologically, 22 cases represented conventional angiomyolipomas, composed of a mixture of adipose tissue, spindle element, epithelioid smooth muscle cells and abnormal thick-walled blood vessels in various proportions. Three cases involving lung, soft tissue and broad ligament had subtle but distinctive morphologic features. Nested or sheet-like architecture with epithelioid or spindle cells was observed. Immunohistochemical study showed that HMB 45, melan A, smooth muscle actin and cathepsin K were expressed in 80% (20/25), 88% (22/25), 88% (22/25) and 100% (25/25) of PEComa, respectively. Within positive cases, the average proportion of positive tumor cells was 36%, 41%, 35% and 90% respectively for HMB 45, melan A, smooth muscle actin and cathepsin K. TFE3 was negative in all of the 22 renal and hepatic PEComa studied, while it was positive in the 3 cases of extra-hepatorenal PEComa. None of the 25 cases exhibited evidence of TFE3 gene fusion or amplification., Conclusions: Extra-hepatorenal PEComa have distinctive morphologic features and are associated with TFE3 overexpression. Cathepsin K immunostaining demonstrates high sensitivity and specificity in PEComa, better than other commonly employed immunomarkers. This marker is thus useful in diagnosis of PEComa and distinction with other neoplasms.

Objective: To study the pathologic features and immunophenotype of 3 cases of melanotic epithelioid clear cell tumor of kidney., Methods: More than 2000 cases of renal tumors were retrospectively reviewed. Three cases of melanotic epithelioid clear cell tumor were identified. Immunohistochemical study was carried out using the paraffin-embedded tissue samples. Electron microscopy was also performed in 1 case., Results: Amongst the 3 cases studied, the male-to-female ratio is 1:2. Histologically, 2 cases showed a clear cell carcinoma-like pattern. Papillary structures covered by clear cells and eosinophilic cells were observed in 1 case. Immunohistochemical study showed that the tumor cells in all cases expressed HMB 45. Two of them were also positive for Melan A. The staining for epithelial markers and S-100 protein was negative. Melanosomes were not identified by ultrastructural examination., Conclusions: Melanotic epithelioid clear cell tumor is a rarely seen neoplasm of kidney. There are some histologic overlaps with renal cell carcinoma, epithelioid angiomyolipoma and melanoma. Immunohistochemical study is useful in confirming the diagnosis. The tumor represents a morphologic variant of epithelioid angiomyolipoma.

Objective: To investigate the clinicopathologic features of tumors showing perivascular epithelioid cell differentiation (PEComas)., Methods: The clinicopathologic data of 39 cases pf angiomyolipoma (AML), 17 males and 22 females, with the primary focus in the kidney on 30 cases, in the liver in 4 cases, in the lung, uterus and broad ligament, abdominal wall, retroperitoneum, and nasal cavity in 1 case respectively, were analyzed. Immunohistochemistry (HIC) was used to detect the expression of pan-cytokeratin (CK), S-100 protein, smooth muscle actin (SMA), desmin, vimentin, HMB45, Melan-A, microphthalmia transcription factor (MiTF), CD117, and CD34 in the specimens of the tumors obtained during operation. Twenty patients were followed up., Results: Pathological examination showed branched capillaries or arterioles, often thick-walled similar to those in the renal cell carcinoma, and the cancerous cells consisting of the mixture of epithelial cells and spindle cells. HIC showed that the expression rates of Melan-A, HMB45, MITF, SMA, desmin, S-100 protein, vimentin, CD117, CK, and CD34 were 95% (37/39), 72% (32/39), 46% (18/39), 82% (32/39), 27% (10/39), 15% (6/39), 82% (32/39), 10% (4/39), 0, and 0 respectively. Clinical follow-up showed 1 patient alive with tumor, and 19 alive free from disease., Conclusion: PEComas have distinctive morphological and immunohistochemical features.

Objective: To study the histopathologic features, differential diagnosis and prognosis of epithelioid angiomyolipoma (EAML) of kidney., Methods: Two cases of EAML (including one case with recurrence) of kidney were retrieved from the archival files of Departments of Pathology, Navy General Hospital of PLA and Health Science Center of Peking University. The clinicopathologic features, immunohistochemistry, ultrastructural findings and follow-up data were studied and literature reviewed., Results: Histologically, the tumors were predominantly composed of epithelioid cells with marked cellular pleomorphism. Focal perivascular arrangement was seen. Hemorrhage and necrosis were present and tumor emboli were found in the venous structures. The renal hilar lymph nodes were also involved by tumor cells. Immunohistochemical study showed that the tumor cells (including those in the hilar lymph nodes) were strongly and diffusely positive for HMB45, smooth muscle actin, neuron-specific enolase and vimentin. They were focally positive for S-100 protein, melan-pan and CD68. The staining for epithelial membrane antigen, AE1/3, CK7, CD117, muscle-specific actin, desmin, leukocyte common antigen, CD20, CD45RO, CD30, CD15, chromogranin A, synaptophysin, bcl-2, estrogen receptor, progesterone receptor and p53 were negative. Ultrastructural examination revealed the presence of melanosome-like dense granules, myofilaments and dense bodies in the tumor cell cytoplasm. Discontinuous and focally thickened basal lamina was seen surrounding the tumor cells. On follow up, both patients remained well and disease-free 10 months after operation., Conclusions: EAML is predominantly or almost entirely composed of epithelioid cells. Perivascular cellular arrangement, focal features of otherwise classic angiomyolipoma, as well as coexpression of HMB-45 and smooth muscle actin are clues to the correct diagnosis. The degree of cytologic atypia, presence of hemorrhage and necrosis and high mitotic activity may indicate the malignant potential of this tumor. On the other hand, the presence of lymph node involvement and even tumor emboli in renal veins may represent multifocaltumorigenicity rather than true malignancy. Definitive evidence of malignancy requires demonstration of distant metastasis.

Objective: To investigate the clinicopathological and immunohistochemical characteristics of hepatic angiomyolipoma (AML) and renal AML, and to compare the similarities and differences between the two., Methods: Hematoxylin-eosin staining and SP immunohistochemical staining were performed on the specimens resected during operation of 12 cases of hepatic AML, 2 males and 10 females, aged 41, and 38 renal AML cases, 14 males and 24 females, aged 43. Wilcoxon rank test was made on the proportions of the 3 kinds of myoid cells and fat tissues., Results: All tumors were composed of three basic components: blood vessels, fatty tissue, and myoid cells epithelioid, spindle, or intermediate in shape. Epithelioid cells accounted for more than 50% of the cells in 6 out of the 12 hepatic AML cases often with apparent cellular and nuclear atypia (12/12), and accounted for less than 25% in all renal AML cases. Spindle-shaped cells were scarcely observed in hepatic AML and were common in renal AML. Nuclear atypia was observed in 20 out of the 38 renal AML cases, 18 cases being mild and 1 being moderate. Fat cells accounted for less than 50% in hepatic AML, and more than 50% in renal AML (P = 0.001). Extramedullary hematopoietic tissue was often seen in hepatic AML but never observed in renal AML. Strong positivity of HMB45 and focal positivity of SMA were common in hepatic AML and strong positivity of SMA and sporadic positivity of HMB45 were observed in the renal AML specimens., Conclusion: The histological composition of AML is highly variable in the proportion and distribution of the 3 component cells between hepatic AML and renal AML.

Objective: To study the morphology of hepatic angiomyolipoma (HAML)., Methods: HE staining, PAS staining, immunohistochemistry and electronic microscopy were used to study 10 cases from our department and 4 cases from consultation., Results: All 14 HAML cases showed perivascular epithelioid cells (PEC) with 4 different types of morphology. They presented characteristic PAS positivity premelanosome like structures and dense body under electronic microscopy. Immunohistochemistry demonstrated positive reaction for both actin and HMB45., Conclusion: Light and electronmicroscopic features and immunophenotype of HAML are characteristic of PEC related lesion.