title: Perivascular epithelioid cell tumor of the rib.
abstract: We present a rare case of perivascular epithelioid cell tumor (PEComa) in the right 6th rib of a 28-year-old man. A plain computed tomography scan showed a round osteolytic lesion in the right 6th rib. The resected tissue contained a globular-shaped, soft tumor. Histologically, the tumor was rich in vasculature and exclusively composed of perivascular epithelioid cells with clear cytoplasm. Immunohistochemically, the tumor expressed diffusely a melanocyte marker, human melanoma black-45, and focally a myogenic marker, alpha-smooth muscle actin, but not an epithelial marker, AE1/AE3. Fontana-Masson-positive melanin pigments were present and c-kit receptor tyrosine kinase (CD117), involved in the development of melanocytes but not myogenic cells, was expressed in tumor cells. These findings indicate that the tumor is PEComa with some differentiation into melanocytes. Notably, owing to the unique location of the occurrence, the tumor occupied bone marrow tissues of the rib, resulting that the tumor has the potential for hematogenous metastasis. In spite of the lack of cells with severe atypia, necrosis, and numerous mitoses, tumor cells invaded into surrounding tissues and overexpressed cyclin D1. To the best of our knowledge, this is the first case report of PEComa arising from the rib with the signs of malignant potential.
authors.affiliation: Department of Pathology, Hyogo College of Medicine, 1-1 Mukogawa, Nishinomiya, Hyogo 663-8501, Japan.
authors.forename: Ikuko
authors.initials: I
authors.lastname: Torii
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Kondo
authors.forename: Teruhisa
authors.initials: T
authors.lastname: Takuwa
authors.forename: Seiji
authors.initials: S
authors.lastname: Matsumoto
authors.forename: Yoshitomo
authors.initials: Y
authors.lastname: Okumura
authors.forename: Ayuko
authors.initials: A
authors.lastname: Sato
authors.forename: Fumihiro
authors.initials: F
authors.lastname: Tanaka
authors.forename: Takashi
authors.initials: T
authors.lastname: Nishigami
authors.forename: Seiki
authors.initials: S
authors.lastname: Hasegawa
authors.forename: Tohru
authors.initials: T
authors.lastname: Tsujimura
mesh_terms: D000328:Adult; D000951:Antigens, Neoplasm / Q000032:analysis; D014408:Biomarkers, Tumor / Q000032:analysis; D001859:Bone Neoplasms / Q000473:pathology*; D015622:Epithelioid Cells / Q000473:pathology*; D006801:Humans; D008297:Male; D008544:Melanocytes / Q000473:pathology; D058950:Melanoma-Specific Antigens; D008637:Mesenchymoma / Q000473:pathology*; D009363:Neoplasm Proteins / Q000032:analysis; D012272:Ribs
chemical_list: D000951:Antigens, Neoplasm; D014408:Biomarkers, Tumor; D058950:Melanoma-Specific Antigens; D009363:Neoplasm Proteins