Endometrial glands in ascites secondary to endometriosis

Endometriosis is a quite common gynaecological disease consisting of the presence of endometrial tissue that replicates outside the uterine cavity. Endometriosis generally occurs in the pelvis, most commonly near the ovaries and the dependent areas covered with peritoneum, but it may also occur at remote sites with unusual manifestations. Ectopic endometrial tissue is influenced by hormonal levels of uterine cycle, so it flakes off with the drop of the hormonal peak as normal endometrium. This mechanism causes an inflammatory reaction in the site interested and possible ascites in the case of peritoneal endometriosis (1-3). Pathogenesis of this process determines that the material found is abounding in blood, macrofages phagocyting hemosiderin and inflammatory cells. Fine-needle cytology has been successfully used to diagnose endometriosis by demonstrating the presence of both epithelial and stromal cells in the smears (4-10); conversely, because the vital endometrial tissue is nested in the host tissues and discharged cells are non-vital, the cytological features of the effusions due to endometriosis have been described as quite unspecific being characterized by histiocytes phagocyting hemosiderin, inflammatory cells and mesothelial cells in hemorrhagic background (11-13). Endometrial cells have also been reported in these samples, but their cytological features are not specific enough to allow a definite cytological diagnosis of endometriosis nor to exclude even a neoplastic process (13). In fact possible diagnostic pitfalls in peritoneal washing in cases of endometriosis have been reported (13,14). In these cases, laparotomy and microscopic examination of tissue are generally requested for diagnosis. We report a case of ascites in a patient suffering from endometriosis, in which the glandular endometrial structures were observed at the cytological examination of the effusion. This 34 year old patient, quite suddenly developed ascites. Paracentesis was performed and 500 ml of hemorrhagic fluid were submitted for cytological examination. Papanicolaou stained cytospins showed mesothelial cells and histiocytes in a hemorrhagic background. Some groups of monomorphous small cells tightly attached to each other were also observed (fig.1); they showed small nuclei with dispersed chromatin and small nucleoli and cytoplasm was scanty and well defined in a honeycomb pattern. These groups were organized in a double layer thinning out to a wide monolayered edge in a typical glove shape (fig.1). The bland microscopic features of these cells ruled out a neoplastic effusion, and moreover these groups strongly suggested the endometrial glandular structures observed in endometrial endocyte (15) as well as in fine-needle cytology of endometriosis (4-10); therefore peritoneal involvement by endometriosis was diagnosed. The patient underwent to proper therapy without other diagnostic procedure. We report this case because the detection of endometrial glandular structure in peritoneal effusion is very unusual. Nonetheless its detection may allow cytological diagnosis of endometriosis in effusions, avoiding more invasive diagnostic procedures.