title: Renal oncocytoma with intracytoplasmic lumina: a case report with ultrastructural findings of "oncoblasts".
abstract: The authors present a case of renal oncocytoma with numerous intracytoplasmic lumina in a 45-year-old woman, with an emphasis on the ultrastructural findings of so-called oncoblasts. The tumor was located in the upper pole of the left kidney, measuring about 3.3 cm in diameter. Histologically, it was composed of solid nests or acinar growths of so-called oncocytic tumor cells with numerous intracytoplasmic lumina and scattered foci of so-called oncoblasts. The luminal surface was positive for Hale's colloidal iron stain. A very small number of glycogen-containing cells were found scattered in a few nests. Immunohistochemically, tumor cells were positive for cytokeratin and epithelial membrane antigen, but negative for vimentin and carcinoembryonic antigen. The Ki-67 labeling index was 1.2%. All of the Ki-67-positive cells were oncocytes. So-called oncoblasts were negative for Ki-67. Ultrastructural examination revealed that the predominant tumor cells had cytoplasm packed with round mitochondria and the mitochodria had lamellar long cristae. So-called oncoblasts showed scant cytoplasm with a moderate number of small mitochondria. Some of them showed pyknosis which can be regarded as mitochondrial involution. The authors believe that so-called oncoblasts are damaged or involuted oncocytes rather than precursors of oncocytes.
authors.affiliation: Department of Laboratory Medicine, National Defense Medical College Hospital, Tokorozawa, Saitama, Japan. taka-emi@fj8.so-net.ne.jp
authors.forename: H
authors.initials: H
authors.lastname: Shimazaki
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
authors.forename: S
authors.initials: S
authors.lastname: Aida
authors.forename: S
authors.initials: S
authors.lastname: Tamai
authors.forename: K
authors.initials: K
authors.lastname: Seguchi
authors.forename: M
authors.initials: M
authors.lastname: Hayakawa
mesh_terms: D018249:Adenoma, Oxyphilic / Q000737:chemistry / Q000648:ultrastructure*; D002272:Carcinoembryonic Antigen / Q000032:analysis; D002466:Cell Nucleolus / Q000648:ultrastructure; D002467:Cell Nucleus / Q000648:ultrastructure; D003593:Cytoplasm / Q000648:ultrastructure; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007633:Keratins / Q000032:analysis; D019394:Ki-67 Antigen / Q000032:analysis; D007680:Kidney Neoplasms / Q000737:chemistry / Q000648:ultrastructure*; D008854:Microscopy, Electron; D008875:Middle Aged; D008938:Mitosis; D018396:Mucin-1 / Q000032:analysis; D014746:Vimentin / Q000032:analysis
chemical_list: D002272:Carcinoembryonic Antigen; D019394:Ki-67 Antigen; D018396:Mucin-1; D014746:Vimentin; D007633:Keratins