title: Ultrastructural Characterization of Mammary Analogue Secretory Carcinoma of the Salivary Glands: A Distinct Entity from Acinic Cell Carcinoma?
abstract: Mammary analogue secretory carcinoma (MASC) of the salivary glands is a recently described neoplasm of the salivary glands with a characteristic morphology complemented by a specific cytogenetic translocation and gene rearrangements. Although immunophenotypic and cytogenetic differences allow for a more reliable distinction, ultrastructural features can also provide important information about the relationship between MASC, classic acinic cell carcinoma (AciCC), and AciCC intercalated duct cell-predominant variant. Following approval from the hospital's institutional review board, 7 cases of MASC, 8 cases of classic AciCC, and 4 cases of AciCC intercalated duct cell-predominant variant were retrieved from the pathology files of Massachusetts General Hospital from 2012 to 2015. Electron microscopy was performed using formalin-fixed, paraffin-embedded tissue. Ultrastructural features of all 19 neoplasms of the salivary glands were recorded. The predominant cell-types observed in MASC are those with intercalated/striated duct cell differentiation. These features include prominent invaginations of the cell surface studded with microvilli, and some intra- and intercellular lumina also with a microvillous surface. Classic AciCC dominant cell-type recapitulates acinar cell differentiation. These cells contain large intracytoplasmic zymogen-like granules. AciCC intercalated duct cell-predominant variant showed both cell populations in various proportions with the intercalated/striated duct cell type usually being the dominant one. MASC presents with distinctive ultrastructural features that allows its proper differentiation from classic AciCC. However, significant ultrastructural features overlaps between both AciCC intercalated duct cells-predominant and classic AciCC and MASC. These findings indicate a very close proximity between these tumors.
authors.affiliation: Department of Pathology, University of Montreal Hospital Center, Montreal, QC, Canada.|Department of Pathology and Molecular Biology, N-528 Faculté de Médecine, Université de Montréal, 2900 Boulevard Edouard-Montpetit, Montreal, QC, H3C 3J7, Canada.
authors.forename: Julie
authors.initials: J
authors.lastname: Guilmette
authors.affiliation: Pathology Service, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.|Department of Pathology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA, 02114-2696, USA.
authors.forename: Gunnlaugur P
authors.initials: GP
authors.lastname: Nielsen
authors.affiliation: Pathology Service, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.|Department of Pathology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA, 02114-2696, USA.|Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, MA, 02114, USA.
authors.forename: William C
authors.initials: WC
authors.lastname: Faquin
authors.affiliation: Pathology Service, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.|Department of Pathology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA, 02114-2696, USA.
authors.forename: Martin
authors.initials: M
authors.lastname: Selig
authors.affiliation: Pathology Service, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.|Department of Pathology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA, 02114-2696, USA.
authors.forename: Vânia
authors.initials: V
authors.lastname: Nosé
authors.affiliation: Pathology Service, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.|Department of Pathology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA, 02114-2696, USA.
authors.forename: Anthony W S
authors.initials: AWS
authors.lastname: Chi
authors.affiliation: Pathology Service, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA. psadow@mgh.harvard.edu.|Department of Pathology, Massachusetts General Hospital, 55 Fruit Street, Boston, MA, 02114-2696, USA. psadow@mgh.harvard.edu.|Department of Otolaryngology, Massachusetts Eye and Ear Infirmary, Boston, MA, 02114, USA. psadow@mgh.harvard.edu.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Sadow
mesh_terms: D000328:Adult; D000368:Aged; D018267:Carcinoma, Acinar Cell / Q000648:ultrastructure*; D005260:Female; D006801:Humans; D008297:Male; D000069295:Mammary Analogue Secretory Carcinoma / Q000648:ultrastructure*; D008875:Middle Aged; D012468:Salivary Gland Neoplasms / Q000648:ultrastructure*; D055815:Young Adult
keywords: Acinic cell carcinoma; Electron microscopy; Mammary analogue secretory carcinoma; Salivary gland tumor