title: Papillary Immature Metaplasia of the Anal Canal: A Low-grade Lesion That Can Mimic a High-grade Lesion.
abstract: In a natural history study of anal human papillomavirus (HPV) infection and HPV-related lesions among homosexual men in Sydney, Australia, we identified 15 examples of papillary immature metaplasia (PIM) in anal biopsy samples. PIM has previously been described in the cervix, but not in the anal canal. PIM is a form of exophytic low-grade squamous intraepithelial lesion (eLSIL) also known as condyloma. In contrast to the maturing keratinocytes and koilocytosis seen in conventional eLSIL, the slender papillary structures of PIM have a surface population of immature squamous cells. In our anal samples PIM was characterized by close proximity to conventional eLSIL, was negative for p16 (p16) expression, and revealed the presence of a single low-risk HPV genotype (either 6 or 11) in laser capture microdissected lesions. The clinical significance of recognizing PIM lies in preventing misdiagnosis as high-grade squamous intraepithelial lesion, (the presumed precursor to anal cancer), due to the morphologic immaturity of the cell population. In routine practice, awareness of anal canal PIM and p16 immunostaining will prevent this. Further study of the natural history of anal canal PIM is needed.
authors.affiliation: *Douglass Hanly Moir Pathology ∥St Vincent's Hospital ¶The Kirby Institute, UNSW Australia #Western Sydney Sexual Health Centre, University of Sydney **RPA Sexual Health, Sydney Local Health District, Sydney, NSW †Regional HPV Labnet Reference Laboratory, Department of Microbiology and Infectious Diseases, The Royal Women's Hospital ‡Murdoch Childrens Research Institute §Department of Obstetrics and Gynaecology, University of Melbourne, Vic., Australia.
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Roberts
authors.forename: Alyssa M
authors.initials: AM
authors.lastname: Cornall
authors.forename: Deborah
authors.initials: D
authors.lastname: Ekman
authors.forename: Carmella
authors.initials: C
authors.lastname: Law
authors.forename: I Mary
authors.initials: IM
authors.lastname: Poynten
authors.forename: Fengyi
authors.initials: F
authors.lastname: Jin
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Hillman
authors.forename: David J
authors.initials: DJ
authors.lastname: Templeton
authors.forename: Sepehr N
authors.initials: SN
authors.lastname: Tabrizi
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Garland
authors.forename: Julia K
authors.initials: JK
authors.lastname: Thurloe
authors.forename: Andrew E
authors.initials: AE
authors.lastname: Grulich
authors.forename: Annabelle
authors.initials: A
authors.lastname: Farnsworth
mesh_terms: D000328:Adult; D001003:Anal Canal / Q000473:pathology* / Q000821:virology; D001005:Anus Neoplasms / Q000737:chemistry / Q000473:pathology* / Q000821:virology; D014408:Biomarkers, Tumor / Q000032:analysis; D001706:Biopsy; D003218:Condylomata Acuminata / Q000378:metabolism / Q000473:pathology* / Q000821:virology; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000032:analysis; D004279:DNA, Viral / Q000235:genetics; D003937:Diagnosis, Differential; D018451:Homosexuality, Male; D061809:Human Papillomavirus DNA Tests; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008679:Metaplasia; D008875:Middle Aged; D060787:Neoplasm Grading; D009517:New South Wales; D027383:Papillomaviridae / Q000235:genetics; D011230:Precancerous Conditions / Q000737:chemistry / Q000473:pathology* / Q000821:virology; D011237:Predictive Value of Tests
chemical_list: D014408:Biomarkers, Tumor; D019941:Cyclin-Dependent Kinase Inhibitor p16; D004279:DNA, Viral