These are formed from the dropsical distension of one of the tubules of the parovarium, or organ of Rosenmüller, which lies between the folds of the broad ligament and between the ovary and the oviduct. Usually, one tubule alone is affected, and the cyst is then unilocular; but exceptional cases have been met with in which several of the tubules have become dilated, and the cyst is then bilocular or even multilocular.9 These cysts are often called cysts of the broad ligament.
9 "Bursting Cysts of the Abdomen," by Wm. Goodell, Trans. American Gynæc. Soc., 1881, p. 231.
By examining cysts in their early stage Albert Doran has demonstrated that "the vertical tubes of the parovarium are lined with epithelium, sometimes ciliated, but oftener cubical, the original, primitive form of the tubes of the Wolffian body. From these tubes and from the hilum of the ovary, full of Wolffian relics, spring the multilocular papillary cysts which give so much trouble to the operator. At the outer end of the horizontal tube of the parovarium is a cystic dilatation which is lined with a structure resembling endothelium. Apart from the parovarium, between the folds of the broad ligament, minute cysts are frequent. It is from these and from the terminal cyst of the parovarium that the simple unilocular so-called parovarian cyst arises. The terminal cyst of the Fallopian tube never attains a large size, and no true cysts of the broad ligament appear, when young and minute, to arise from that tube."10
10 British Med. Journal, Oct. 21, 1882, p. 792.
These cysts are more commonly found in young women. From the thinness of their walls and the limpid character of their fluid, they yield very marked waves of fluctuation which are equally distinct at every point. They can usually be distinguished from ovarian cysts either by a lack of that tenseness so characteristic of the latter or by varying conditions of tenseness and flaccidity, as if the fluid were sometimes absorbed more quickly than at other times. They also grow more slowly than the ovarian cyst, and do not exert the same profound constitutional impression. The facies ovariana is absent, and the health of the woman may in no wise be disturbed. They, indeed, in the majority of cases, seem to do no harm, and are merely annoying from their bulk. The fluid they contain is with rare exceptions as limpid and clear as spring-water, but with refractive powers so high as to magnify the fibres of the wooden pail into which it has been drawn off.
Owing to their very thin walls and delicate structure these cysts on very slight provocation are liable to burst. On account of the blandness of the contained fluid this accident is rarely followed by collapse or by peritonitis. The rent heals up and the cyst usually refills; but in a large proportion of cases it does not, and the woman remains permanently healed.11 Sometimes they are pedunculated, but often they lie between the two folds of the broad ligament, having no proper stalk.
11 "Bursting Cysts of the Abdomen," by Wm. Goodell, Trans. American Gynæcological Society, 1881, p. 226.
Cysts of the broad ligament must not be confounded with those ovarian cysts which, instead of growing free in the peritoneal cavity, develop between the two layers of the peritoneum—intra-ligamentous ovarian cysts, as Garrigues very aptly calls them in his paper on the "Diagnosis of Ovarian Cysts."12 In this excellent paper, from which I have gleaned much, he says that sometimes the anatomical relations are so lost that nothing short of a microscopic examination of the outer epithelium can determine the character of the cyst. Thus, "a tumor covered with columnar epithelium is ovarian, and cannot be anything else; while the cyst of the broad ligament, being covered with peritoneum, has flat peritoneal endothelium. In cases of intra-ligamentous development of an ovarian cyst the lower portion is covered by peritoneum, but the upper part has the columnar epithelium characteristic of the ovary." There are, however, certain macroscopic characteristics which will generally tell the nature of the cyst. For instance: usually by a careful examination the corresponding ovary will be found either stretched out and spread out in the wall of the sac, or, what in my experience is more common, elongated and forming a part of the stalk. These cysts are in the vast majority of cases monocysts, while unilocular ovarian cysts are very rarely if ever met with. Their walls are thin, of a conjunctival blue, and fretted with a delicate network of blood-vessels. The oviduct is usually imbedded in the cyst, and by transmitted light its fimbriæ can be traced out in the cyst-walls in long fronds as delicate as those of dried and pressed seaweed. Then, again, the peritoneal coat is readily stripped off. On the other hand, in an ovarian tumor the oviduct is not ordinarily incorporated in the cyst-wall; in fact, a meso-salpinx usually exists; and, further, the peritoneal coat, being nailed down to the cyst-wall proper by the cicatrices of ovulation, is not capable of being stripped off.
12 Am. Journ. of Obstetrics, April, 1882, p. 394.