title: Solid Variant of Adenoid Cystic Carcinoma: Difficulties in Diagnostic Recognition.
abstract: Adenoid cystic carcinoma (ACC) is a malignant neoplasm that mainly affects the salivary glands but has been described in many other anatomical sites. It is composed of basaloid cells with myoepithelial/basal cell differentiation and ductal epithelial cells that proliferate in a fibrous stroma, with variable amounts of myxohyaline material. Three patterns (cribriform, tubular, and solid) occur, and the solid variant is characterized by a predominant compact sheet-like and nested pattern of rounded basaloid cells lacking obvious cribriform or tubular architecture. The solid variant has significant morphological and immunohistochemical overlap with a large range of neoplasms of different lineages, including other carcinomas and sarcomas. We describe a case of solid variant ACC of the paranasal sinuses, which showed an almost entirely solid pattern of growth (in >95% of cells) and which on initial biopsy showed no features of classical ACC. This highlights the potential for diagnostic misinterpretation with a variety of other neoplasms, which is particularly important because of the significant difference in treatment for ACC and tumors in its differential diagnosis.
authors.affiliation: Royal Marsden Hospital, London, UK.
authors.forename: Imen
authors.initials: I
authors.lastname: Ben Salha
authors.affiliation: Royal Marsden Hospital, London, UK.
authors.forename: Shree
authors.initials: S
authors.lastname: Bhide
authors.affiliation: Royal Marsden Hospital, London, UK.
authors.forename: Despoina
authors.initials: D
authors.lastname: Mourtzoukou
authors.affiliation: Royal Marsden Hospital, London, UK.
authors.forename: Cyril
authors.initials: C
authors.lastname: Fisher
authors.affiliation: Royal Marsden Hospital, London, UK khin.thway@rmh.nhs.uk.
authors.forename: Khin
authors.initials: K
authors.lastname: Thway
mesh_terms: D014408:Biomarkers, Tumor / Q000032:analysis; D003528:Carcinoma, Adenoid Cystic / Q000175:diagnosis / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008875:Middle Aged; D012468:Salivary Gland Neoplasms / Q000175:diagnosis / Q000473:pathology*
chemical_list: D014408:Biomarkers, Tumor
keywords: adenoid cystic carcinoma; head and neck; paranasal sinus; pathology; solid variant