The following is abstracted from Human Tumors, Histology, Diagnosis and Technique, By Pierre Masson (1880-1959), Professor, University of Montreal, Wayne State University Press, 1970. Translated by Sidney D. Kobernick, M.D., Ph.D., Director of Laboratories, Sinai Hospital of Detroit, Associate Professor, Department of Pathology, Wayne State University School of Medicine. ===================================================================== From: Chapter Six, Genital Apparatus: Single Tissue Neoplasms of Immature Embryomas These neoplasms, which are tumors of tumors, can appear at any moment in the evolution of an embryoma. Some originate from one or the other of the embryonal forms of the constituents studied above. They are th emost frequent. Their usual point of departure is the trophoblast, more rarely the ectoblast, and most rarely the endoblast, and the last only in the ovary where the endoblast can be the origin of more or less massive enteroid epitheliomas. Others develop from more differentiated tissues: cerebrospinal nerve tissue, striated muscle, smooth muscle, cartilage and bone. Finally, some appear to have several different tissues as their point of departure but of which certain ones become preponderant and alone (save exceptions) give rise to metastases. Trophoblastomas The first published observation of a testicular tumor, whose propagation into the pelvic veins had filled the latter with polypoid masses comparable to that of a hydatidiform mole, was by Waldeyer (1868). After him, Malassez interpreted similar instances as angioplastic sarcomas. Schlagenhaufer (1901) confirmed the analogy of these tumors to those of the fetal placenta and called them *chorio-epitheliomas.* This name appears even more justified at the present time since these tumors produce the same hormones as those of the uterus, and since they are ac- companied by a strongly positive Aschheim-Zondek reaction and often by [page 849] gynecomastia. However, chorio-epitheliomas originating in the testis--or ovary--are not the only trophoblastic tumors possible. Only these are encountered in the uterus where they develop form a trophoblast very differentiated by a pregnancy. Since 1919 A.Peyron, in one of his charac- teristically penetrating studies, extended broadly the scope of tropho- blastic tumors of the testicle in relating them to neoplasms not pre- viously understood with a structure comparable to that of the *primitive trophoblast at the beginning of its evolution: that is to say, at the moment when the external cellular layer of the blastula gives rise both to the extra-embryonic mesenchyme and to the chorionic epithelium.* Too far in advance of their times, these works of Peyron (like those which he -------------------------------------------------------------------- [Fig. 6.42. Testis. Very primitive trophoblast at the beginning of its reticular evolution] [Insert 1, overall view of an embryoid form surrounded by fibrous tissue m. Its amniotic lining is deformed in t, and bordered in 2 by compact trophoblastic masses (insert 2) being transformed into mesenchyme. This trophoblastic region t is represented in the large figure. Its lacunae contain numerous hyaline, very acidophilic spherules.] --------------------------------------------------------------------- [page 850] subsequently published on the polyembryony of the embryomas) re- mained uncomprehended and forgotten. Without knowing them, Gunnar Teilum arrived at a similar concept when he described "embryonic mesoblastomas" of which J.F. Martin, F. Cabanne, and J. Feroldi have just made an excellent study. In order to understand the peculiarities, it is well to review briefly the evolution of the primitive trophoblast. At the beginning, the trophoblast is composed of the external stratum of the morula. From the implantation of the embryo into the uterine mucosa, this primitive trophoblast separates itself from the embryonic plate and its cells, in proliferating, lose their epithelial ar- rangement, form a mass of irregularly arranged cells which continue to envelop the embryonic plate, and invade the uterine mucosa. Around the blastocyte, arising from the plate, it is transformed into an increas- ingly lacunar tissue, the extra-embryonic mesenchyme, until its external portion is partly substituted for the endothelium of the uterine vessels, and becomes the chorio-epithelium with its syncytial lining and Lang- hans cells. I have already emphasized that the normal extra-embryonic mesenchyme is not vascularized from the beginning. It will not be, except by the embryo when it develops its circulatory apparatus. The embryonic forms studied above are included in an already constituted extra-embryonic mesenchyme, *anachronistically vascularized* and concealing scattered plasmodial elements which suggest a rudi- mentary chorio-epithelial evolution. *These elements are interesting in that they explain the double potential, mesenchymatous and chorio- epithelial, of the tumor trophoblast.* Nevertheless, the earliest evolu- tionary stages of the trophoblast are not apparent in them. One can, however, observe them in certain embryomas where the embryoid forms are dispersed in the fibrous connective tissue as in figure 6.42. Then it may be seen in contact with the amniotic wall and deforming it locally, as a confused mass of cells. Compact in comparison to the surrounding cells, this mass becomes lacunar and reticulated at its borders and tends to isolate the amniotic cyst from the neighboring tissue (fig.6.42). Such ob- servations show that the reticular matrix which envelops the embryoid forms does not correspond to a primary tissue *sui generis,* but represents a state of relative differentiation of a still more primitive tissue which had preceded it and which is reminiscent of the trophoblast at the begin- ning of its normal evolution. From these facts, one may consider that certain neoplasms of the gonads can present structures which recall with some fidelity the histogenetic steps of the primitive trophoblast and for which the most perfect term would be chorio-epithelioma. Now these neoplasms exist, but not having been understood, they were included in the vague and confused group of *teratocarcinomas,* or in those of the *mesonephromas* of W.Schiller. -----------------------------