Plasmacytoma of the mandible.

Abstract 1. 1. A case of plasmacytoma of the mandible is presented. 2. 2. Protein electrophoresis studies are discussed. 3. 3. The probable relation between plasma cells and gamma globulin is noted. Because of the important revelations made by the electrophoretic analyses of both the serum and the tumor tissue in this case I thought it might be of interest to learn something of the apparatus and methods of analysis that were employed. I therefore asked Professor Moore, who did these analyses to comment on this subject. (L. R. C.) Prof. Dan. JH. Moore. ∗ —Electrophoresis is the migration of colloidal particles under the influence of an electric current. This gives us a method of separating the various components of proteins which cannot be done chemically or by other physical means. The electrophoresis analyses were carried out by the use of the Tiselius apparatus. 1 This consists of a U-tube having a rectangular cross-section, the end walls of which have a high optical quality so that light refraction caused by concentration gradients in the solution can be detected accurately. The colloidal solution is placed in the bottom section and in one limb of the U-tube in such a way that sharp boundaries are formed between the solution and a buffer against which the solution had been dialyzed until its conductivity and pH assumed approximately the same value as that of the buffer. To facilitate filling and recovery of material after separation, the electrophoresis cell (U-tube) is divided into sections with sliding flange plates, so that each section may be sealed off from the rest of the system. The tops of the U-tube connect to large buffer vessels containing electrodes. The whole is placed in a water bath thermostatically maintained at a low temperature (0.0° C. in our work). A boundary is formed by aligning the sections containing the colloidal solution with the rest of the cell. A constant voltage applied to the electrodes causes a current to flow (since the solutions are conducting). Convectional disturbances due to heat are minimized by maintaining the mean temperature (temperature is highest at center and lowest at walls of cells) of the solution at the point where the change of density with temperature is least (temperature of maximum density). Convection limits the wattage which may be dissipated in the cell. The current produces an electrical field throughout the cell. If the cell has uniform cross-sectional area, A, cm. 2 , the field E equals I KA where I is the current in amperes and K is the specific conductance of the solution in reciprocal ohms. This electric field causes the different components of the colloidal mixture to migrate at a rate proportional to the statistical surface charge per unit area of the particles or molecules and in a direction determined by the sign of this charge. This rate of migration in cm./sec. per unit field in volts per cm. is designated as the mobility of the component. Bending of light rays caused by concentration gradients at the boundaries of each component may be detected by various optical methods; in this work we have used the Toepler Schlieren method with the adaptation of Longsworth. 2 A simple diagram of the optical method is illustrated (Fig. 6). A horizontal source slit S illuminates the Schlieren lenses L 1 and L 2 between which is located the electrophoresis cell C (U-tube). These lenses image the source slit in the plane of the moveable edges E . The camera lens, L 3 , causes an image of the cell, C , to fall on the plate P . The electrophoretic patterns are obtained by a synchronized movement of the photographic plate (horizontally) and the Schlieren diaphragm E (vertically). A mask with a narrow vertical slit is placed just in front of the plate to mask out all light except that through the cell limb being scanned. As the Schlieren diaphragm, E , is raised, the first light to enter the camera is that which passes through the strongest refractive index gradient and thus suffers the greatest deviation. As the diaphragm is further raised, those rays which are less deviated are allowed to pass until finally the undeviated light which traverses the cell ahead of, or between, boundaries is transmitted to the plate. The shape of the curve thus obtained indicates the concentration gradients existing at each boundary and the area under each peak corresponds to the total refractive index difference caused by that component. Dr. Lester R. Cahn. —Abnormal protein metabolism is one of the prominent features of multiple myeloma. This is seen in the hyperproteinemia, the increase in gamma globulin, and the inverted albumin-globulin ratio. Also the disease produces an abnormal protein manifested in the urine in some 50 per cent of cases as Bence-Jones protein. On very rare occasions, this protein is found in the spinal fluid. Amyloid, another abnormal protein, is found in 30 per cent of the cases of multiple myeloma. It is believed that the plasma cells are responsible for the changes in protein metabolism and for the formation of the abnormal protein. It would seem that Dr. Lane's case offers a strong suggestion that the plasma cells were responsible for the changes in the serum protein. As he stated, they had a tumor composed of almost 100 per cent plasma cells, and the electrophoretic analysis showed the increase in the protein to be the gamma globulin fraction in both the tissue and the patient's serum. After operation the gamma globulin curve returned to normal as did the albumin-globulin ratio, all of which showed that the small tumor of plasma cells exerted the influence accountable for the protein changes. Histologically the tumor resembled the type of lesion seen in multiple myeloma. Biochemically the changes found in the serum resembled those seen in myeloma. These biochemical changes were mild because of the single lesion, but nonetheless were significant. This case shows that there may be a difference between plasma cell tumors, and that the differentiation cannot be made by the microscope but only by chemical and electrophoretic studies. Further investigation along this line is in order. It is quite unlikely that the tumor just reported will recur locally as it has been completely removed. However, similar tumors may occur in other parts of the skeleton. If this should take place it would indicate that myeloma is multicentric in origin, which is the general belief. Future skeletal involvement in this instance could not be said to be due to metastasis, since there was no such evidence at the time of operation, and since the biochemical and electrophoretic changes returned to normal after the removal of the lesion. If this patient, after a reasonable lapse of years, should remain free from disease, then it might be said that there is a strong possibility that myeloma starts as a local disease, which, if removed early enough, will result in cure. Finally, the serum of every patient with a plasma cell tumor, no matter how innocuous it may appear, should be studied biochemically and electrophoretically. If changes are noted such as occurred in this case, wide surgical excision, so as to accomplish complete ablation, is indicated.