title: Ectopic hamartomatous thymoma: a case report showing CD99+ lymphocytes and a low proliferation index.
abstract: Ectopic hamartomatous thymoma is a rare benign tumor that consists of spindle, epithelial, and adipose cell elements. We present a case of this lesion arising in the supraclavicular region of a 59-year-old man, including the characteristic immunohistochemical and ultrastructural findings. DNA flow cytometry revealed diploidy with a low proliferation index (6.73%). The tumor contained CD99+ lymphocytes; CD99 (MIC2) can serve as a useful marker of immature T cells. These findings suggest that ectopic hamartomatous thymoma may develop from the third branchial pouch or thymic anlage.
authors.affiliation: Department of Pathology, Medical College, Ewha Womans University, Seoul, South Korea.
authors.forename: Shi Nae
authors.initials: SN
authors.lastname: Lee
authors.forename: Min Sun
authors.initials: MS
authors.lastname: Cho
authors.forename: Heasoo
authors.initials: H
authors.lastname: Koo
authors.forename: Woon Sup
authors.initials: WS
authors.lastname: Han
mesh_terms: D000071443:12E7 Antigen; D015703:Antigens, CD / Q000032:analysis; D018952:Antigens, CD34 / Q000032:analysis; D017252:CD3 Complex / Q000032:analysis; D015815:Cell Adhesion Molecules / Q000032:analysis; D002455:Cell Division; D002828:Choristoma / Q000378:metabolism / Q000473:pathology*; D006222:Hamartoma / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D006801:Humans; D007150:Immunohistochemistry; D007633:Keratins / Q000032:analysis; D017493:Leukocyte Common Antigens / Q000032:analysis; D008214:Lymphocytes / Q000737:chemistry / Q000473:pathology; D008297:Male; D008854:Microscopy, Electron; D008875:Middle Aged; D008940:Mitotic Index; D018396:Mucin-1 / Q000032:analysis; D013945:Thymoma / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure; D013953:Thymus Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000648:ultrastructure
chemical_list: D000071443:12E7 Antigen; D015703:Antigens, CD; D018952:Antigens, CD34; D017252:CD3 Complex; C061828:CD99 protein, human; D015815:Cell Adhesion Molecules; D018396:Mucin-1; D007633:Keratins; D017493:Leukocyte Common Antigens