THE AMERICAN JOURNAL of CANCER a Continuation of the Journal of Cancer Research

THE AMERICAN JOURNAL OF CANCER A Continuation of The Journal of Cancer Research ~ VOLUMEXXXIV DECEMBER,1938 NUMBER4 SYNOVIAL SARCOMAS IN SEROUS BURSAE AND TENDON SHEATHS PROF. LOUIS BERGER, M.D. (From the Pathological Department, HBpital de I'Enfant-Jdsus, and the Anti-Cancer Center of Lava1 University, Quebec) Progress in the knowledge of malignant tumors arising from synovial tissue has been slow. In spite of some recent and valuable contributions, this chapter is far from complete. The reasons for this are threefold: first, the want of knowledge concerning the normal features and nature of synovial tissue, which was long studied in articulations only, although it is common, also, to serous bursae and tendon sheaths; second, the relative-perhaps only apparent-rarity of cases; finally, the lack of precision and even vagueness of the reports in the literature., Most of the older authors, and even some contemporary ones, interested primarily in the clinical or surgical aspects of the question, have been satisfied with a purely topographical diagnosis and have either neglected the histologic aspects of their tumors or described them only briefly and superficially. We have had the opportunity of studying five cases of synovial sarcoma, differing more or less from one another but all originating outside of articulations, that is in serous bursae or tendon sheaths, where these tumors are less known, but perhaps easier to study than in the more intricate tissues of the joints. THENORMAL SYNOVIAL TISSUE The prototype of synovial tissue is encountered in the synovial membranes of the joints, but all histologists admit that the lining tissue of the serous bursae and tendon sheaths is homologous with articular synovialis. It consists of a dense connective tissue through which are scattered polymorphous cells. It is possible to distinguish an outer, vascular and fatty portion and an inner or superficial, lamellated layer containing dendritic cells. Some of the latter at- tain the surface, but the lining most often appears discontinuous, formed here 501 502 LOUIS BERCER by the bodies, there by the extensions of branching cells, between which are apparently bare portions of collagenous substance. In some recesses and on the surface of synovial villi the lining is more regular and quite continuous, built up by approximately cuboidal cells. The histologic structure of synovial tissue appears, therefore, quite simple, but it has been variously interpreted. The synovial membrane was first believed to be some sort of epithelium, but soon afterwards was classified as endothelium, a conception which long prevailed and is still held by many authors. Others, with Lubosch, regard it as a modified cartilaginous tissue, or, with Tourneux and Hammar, as of cartilaginous derivation. This opinion may appear convincing for the synovial membranes of the joints, where histo- genetically the anlage of synovial and cartilaginous tissue seems to be the same, but it is not easily acceptable for tendon sheaths, and even less so for bursae, which are very often independent of or remote from any cartilage. Although some histologists (Schaeffer ) and many pathologists (Kaufmann, Aschoff) adhere to the endothelial interpretation, others, as for example, Key, consider the lining too irregular to be consistent with an endothelial nature. They believe that the lining cells are ordinary fixed connective-tissue cells, the form of which-and perhaps also the function-is slightly modified by their superficial situation. Key, in particular, conceded only an endothelial (‘aspect ” to these cells. More recently Franceschini has brought forward a new conception of synovial membranes. He distinguishes two types of tissue: the first, a very simple one, resembling in appearance ordinary fibrous tissue, is encountered where the mechanical stress intrinsic to articular function directly exercises its effects; the second, which is more differentiated, is limited to areas less exposed to pressure and friction. The cells of the second type are surrounded by numerous reticular fibrils, and Franceschini concludes that these cells form a true reticulo-histiocytic meshwork, the superficial layer of which would give, after desquamation and regressive metamorphosis, the polymorphous elements encountered in the synovial fluid. Key objected to this hypothesis, but Sabraz&s, De Grailly and Salabartan confirmed and extended Franceschini’s conclusions. They believe that the superficial cells undergo a peculiar adap- tation, without, however, the attainment of a truly regular structure. Some of the lining cells become flat and endothelium-like, adequate for a border r81e and perhaps incapable of differentiating further : others are transformed into histiocytes and functional monocytic cells which may emigrate and enter the synovial fluid. The most recent studies are those of Vaubel, who showed that cultures of synovial tissues differ entirely from cultures of other mesenchymal cells, in particular from those of the cutaneous and interstitial variety: “ The pe- culiarity of a synovial growth rests in part on the polymorphism of the cells, the countour of which ranges from round and spindle to polygonal and epithe- lioid, and especially on their tendency to form membranes composed of syncy- tial elements.” Although synovial cultures resemble to some degree those of growing osteoblasts or chondroblasts, Vaubel nevertheless regards synovial cells as different from either of these, forming an autonomous cell type with peculiar morphological and junctional properties; he even proposes for them SYNOVIAL SARCOMAS IN SEROUS BURSAE AND TENDON SHEATHS 503 the specific designation “ synovioblasts.” According to Vaubel, the essential function of these cells is the formation of synovial fluid, and the synovial mucin is analogous to the intercellular substance of cartilage, from which it differs chiefly in its lack of solidification. Vaubel avoids applying to this formation of mucin the term “secretion,” which he believes should be re- stricted to the enzyme-forming function of epithelial glands. Opinions as to the origin of the synovial fluid and the mechanism of its formation are not less varied. In the eyes of the older authors (Bichat, Todd) the articular fluid was a simple transudate. v. Koelliker believed that this transudate was modified by the influence of articular “ epithelium.” Frerichs (1846) was the first to show the presence of mucin and regarded it as coming from the “ serous ” lining through a continuous desquamation of cells and their subsequent dissolution in the alkaline “ serum.” Hueter, however, did not encounter any evidence which would favor such a desquamation and Kling saw in this hypothesis only an erroneous analogy with the disinte- gration of the horny layers of the epidermis. Soubbotine, Mayeda (according to Kling and Vaubel), Aschoff, and Raufmann believed that the mucus is secreted by synovial cells. For W. Mueller, on the other hand, the fluid is not-at least not exclusively-a secretory product of the membrane, but re- sults in large part from a liquefaction of articular lining cells, through some sort of mucinous degeneration, and from a constant flow of liquid from the articular surface. To Sabrazks and his fellow-workers the mucus seems to develop from a premucoid extracellular substance, for only very exceptionally are minute droplets observed in the protoplasm. These authors admit the possibility of a mucinous degeneration of protoplasm and nucleus as a whole; the mucinoid and other (fatty) degenerations observed in synovial membranes represent, in their mind, a debased function through which the synovial fluids acquire some of the chemical elements which are necessary to the lubrication of the articular surface, but which cannot be furnished by transu- dation of plasma alone. King studied the Golgi apparatus in synovial cells and concludes that they participate by active secretion in the fluid formation. He also observed desquamation of lining cells, but the fact that these appeared to be alive and capable of growth and proliferation (Vaubel) seemed to him to contradict the hypothesis of cellular degeneration. King seems, however, in some meas- ure to contradict himself, for he mentions the indistinctness of the outlines of the desquamated cells and the presence of cellular dkbris. Sabrazb, con- trary to King and others, holds the presence of more or less degenerated or senescent desquamated cells to be unquestionable, and illustrates it by convincing evidence. But according to Vaubel, this desquamation, if one accepts it, cannot be linked with mucin, which is not due to such a degenerative process, being encountered only in young and never in degenerating cultures. This necessarily brief review shows that the conceptions of various authors concerning both the synovial tissue and the fluid are far from unanimous. The differences of opinion may be reduced to the following questions: (1) Is the synovial membrane a simple endothelium, a modified cartilage, a reticulo- histiocytic or a truly autonomous and specific tissue? (2) Is the synovial fluid the result of a direct or indirect secretion? Do desquamated and dissolved 504 LOUIS BERCER cellular elements contribute to its formation, and what is the mechanism of mucin formation? It is far from our intention to draw from the study of our tumors definite conclusions as to the nature of their normal substratum. Indeed, this paper is, first of all, a discussion of the pathological aspects of malignant synovial

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