Abstract

Squamous cell carcinoma arising in dermoid cyst or cystic teratoma of ovary occurs rarely in women; its incidence is low and varies from 1.7% to 3%. A non-teratomatous squamous cell carcinoma of ovary is even rarer. Only one or two authentic cases are reported in the literature. Human ovarian squamous cell carcinoma is usually found in benign cystic teratomas which undergo malignant transformation. According to E. R. Novak, histogenesis of teratoma is inadequately established and their relationship to other tumors such as struma ovarii, seromucinous cystadenomata, dysgerminoma and embryonal carcinoma is not clear. Black and Benitez reported a most unusual case of non-teratomatous squamous cell carcinoma in situ of ovary in a 35-year-old woman of Mongolian descent, who was operated on for a large cystic ovary measuring 8.2×6.3×3.4 cm. Three cysts were found on section; one of them was lined by squamous cell carcinoma in situ, and the remaining two were lined by flattened cuboidal epithelium. This certainly indicates that squamous cell carcinoma may haute a non-teratomatous origin in ovary. Black and Benitez suggested that perhaps an atypical squamous metaplasia of the endocervical like epithelium of an ovarian cyst could conceivably progress to an in situ carcinoma. Another case of a primary cystic squamous cell carcinoma was reported to have originated in the areas of squamous metaplasia in a mucinous cystadenoma. Therefore it is quite possible that the Black’s case may well be of the same histogenesis as the case cited above, although in this case the original cyst may have been lined by follicular cells and the latter undergone squamous metaplasia progressing to carcinoma. Since there is a growing evidence in recent years that granulosa cells are mobile as well as derived from the ovarian stroma, it is conceivable that many hormone-producing tumors of ovary also take their origin in the stroma, which is, as R.A. Willis puts it and others concur, not a mere supportive tissue but an undifferentiated blastema that is highly plastic and capable of wide range of metaplastic transformation. Some form of malignant Brenner tumors look very much like primary squamous cell carcinoma of ovary and Shay and Janovski suggested to classify the tumor as epidermoid, adenocarcino matous and mixed type. There are numerous studies and reports on histogenesis and hormonal activity of granulosatheca cell tumor, Brenner tumor, and serous cystadenocarcinoma. Review of the literature makes us believe more strongly that all these tumors, be .it feminizing or musculinizing, are closely related to each other and of the same stromal origin. The current report of an experimental study of mouse ovarian cell cultures and tumors which they induced is presented to support the view that many of these tumors are akin to one another and of common origin in bipotential ovarian cells. The ovarian epithelial and stromal cells were shown to undergo an interchangeable type of differentiation. Knowledge of the conditions under which this ability becomes manifested and of the mechanisms in altering cell differentiation may lead to a better understanding of histogenesis of ovarian tumors, including origin of such unusual type of ovrarian neoplasm as squamous cell carcinoma. An in vitro method of growing epithelial cell cultures isolated from explanted ovary of mouse led to the development of cell lines with tumorigenic properties. Among various neoplasms such as granulosa cell carcinoma and sarcomatoid tumors produced by inoculation of isologous mice, a squamous cell carcinoma was also observed. The description of the method by which this unusual tumor was unexpectedly produced and the demonstration of the usefulness of an in vitro analytical approach to studies of differentiation of various types of ovarian cells and of histogenesis of ovarian tumors are the main objectives of this report.