Morphologic Features of Endometriosis in Various Types of Cytologic Specimens G€ uliz A. Barkan, M.D., 1 * Bernard Naylor, M.D., 2 Paolo Gattuso, M.D., 3 Sevgi K€ ull € u, M.D., 4 Kristine Galan, M.D., 3 and Eva M. Wojcik, M.D. 1 Endometriosis is defined as the presence of endometrial tissue outside the uterine cavity. This study evaluates the cytomorpho- logic features of endometriosis in various cytologic specimen types [fine-needle aspiration (FNA), effusion cytology (EF), touch imprint (ToP), and cervical smear (PAP)], and assesses the key elements helpful in recognizing this lesion. A total of 18 cases (8 FNA, 4 EF, 5 ToP, and 1 PAP) of cytologically diag- nosed and histologically/clinically confirmed endometriosis diag- nosed between 1988 and 2006 comprises the material for this study. The morphologic features evaluated of the three compo- nents included: cellularity, presence of sheets of glandular cells, three-dimensional (3D) glandular clusters, tubular structures, single cells, syncytial groups of stromal cells, stromal cells entrapped within basement membrane (BM)-like material, cyto- logic atypia, presence of mitotic figures, and hemosiderin-laden histiocytes. Endometrial glands, stroma, and hemosiderin-laden histiocytes were all identified in 14/18 (77.8%) cases. FNA specimens were more cellular than that of both EF and ToP specimens. Tubular structures, 3D glandular clusters, stromal cells entrapped in BM and syncytial stromal groups were more common in FNAs, and ToPs compared with the EFs. The ratio of the endometrial glandular and stromal cells was similar in all specimen types. Atypia and mitotic figures were rarely encountered. Diagnosis of endometriosis could be made inde- pendently on either smears/ThinPrep TM slides or on cell blocks in all cases where these preparations were available. On follow up, none of the patients developed malignancy. Endometriosis can be reliably and safely diagnosed in various cytologic mate- rials. Cytologic atypia is uncommon. Components of endometri- osis could show minor morphologic alterations in different specimen types. Diagn. Cytopathol. 2013;41:936–942. V C 2013 Wiley Periodicals, Inc. Key Words: endometriosis; cytology; FNA; effusion Endometriosis is a relatively common disease, defined as the presence of functional endometrial tissue outside the uterus. 1 Ectopic endometrial tissue is identified as endo- metrial glands and stromal tissue usually accompanied by hemosiderin-laden histiocytes. Most of the time, histo- logic identification of two of the three components could be sufficient for the diagnosis. 1 Endometriosis primarily affects women of reproductive age and has symptoms varying from occult to more spe- cific complaints. The most common site for endometriosis is the ovary, 2 although there has been reports of endome- triosis in the uterine ligaments, 3 rectovaginal septum, 4 fal- lopian tubes, 3 rectosigmoid colon, ureter, 5 bladder, 6 umbilicus, 7,8 inguinal, 8 and perianal regions. 9 Endometri- osis could also be scar-related, occurring after operations on the uterus or fallopian tubes particularly in the lower abdominal wall or episiotomy scars. 8,10–12 Cutaneous, scar-related endometriosis presents as a mass/nodule appearing weeks to years following surgery and shows catamenial increase in size and tenderness with occasional bleeding from the lesion. Endometriosis can be managed by either medical or surgical treatment. As previously reported, endometriosis can be accurately diagnosed by aspiration cytology. 4,13–28 Endometriosis has been reported in a variety of specimen types: fine-needle aspiration (FNA), 4,13,16,18,19,26,29 effu- sion samples, 28,30 and cervical smears. 20,22,23,25 According to the different body sites and specimen types, the differ- ential diagnosis may vary, but in most cases, it includes be- nign hemorrhagic cyst, follicular cyst, hematoma, endosalpingiosis, and adenocarcinoma, especially in aspi- rates of intraabdominal, pelvic sites, and effusion fluid 1 Department of Pathology, Loyola University Medical Center, May- wood, Illinois 2 Department of Pathology, University of Michigan, Ann Arbor, Michigan 3 Department of Pathology, Rush University Medical Center, Chicago, Illinois 4 Department of Pathology, Marmara Pathology Laboratory, Istanbul, Turkey *Correspondence to: G€ uliz A. Barkan M.D., Associate Professor of Pathology, Loyola University Medical Center, Department of Pathology, Bldg 110, 2130 South First Ave, Maywood, IL 60153. E-mail: gbarkan@lumc.edu Received 18 February 2011; Accepted 1 January 2013 DOI: 10.1002/dc.22979 Published online 20 March 2013 in Wiley Online Library (wileyonlinelibrary.com). 936 Diagnostic Cytopathology, Vol. 41, No 11 V C 2013 WILEY PERIODICALS, INC.