Collagenous bodies in endometriotic cysts

A 4-yr retrospective analysis of cases diagnosed as pelvic endometriotic cysts based on clinical, radiological, and cytomorphological features was collected and analysed. Out of 15 cases, only 3 cases showed the presence of endometrial glands/stroma in the aspiration smears. However, 12 of them showed the presence of oval/petal-shaped structures throughout the smear ranging in size from 40 to 70 micro in maximum dimension. These structures stained positive with periodic acid Schiff (PAS) stain. Immunostaining for type IV collagen showed strong positivity, indicating their origin from the basement membrane of the glands. The presence of these "collagenous bodies" in endometriotic cysts appears to be characteristic. However, this needs to be confirmed by prospective studies with a larger number of patients. The mechanism of formation of these collagenous bodies is uncertain.