Upsala J Med Sci 84: 255-258, 1979 Estimation of Parenchymal Cell Mass of Parathyroid Glands using a Volumeter Technique Goran Akerstrom', Lars Grimeliu?, Conny Fridh3 and Henry Johansson' From the Departments of Surgery' and Pathology', University Hospital, Uppsala and the Institute of Technology3, Stockholm, Sweden ABSTRACT A volumeter technique was used to estimate the density of the two main tissue components of the parathyroid gland - parenchymal and fat tissue. The difference in density between the two components was distinct ( 1 . 0 6 and 0.93 g/ml) and measurements of the weight and volume of parathyroid glands could therefore be utilized in calculating their parenchymal tissue content. The results of these measurements corresponded to those obtained at histopathological evaluation of parathyroid glands. The presented technique is simple and convenient and with slight improvement could be used for intraoperative characterization of para- thyroid glands. INTRODUCTION Normal parathyroid glands contain parenchymal and fat cells and a minimal amount of stroma. The parenchymal cell mass probably best reflects the glandular endocrine activity. However, there are difficulties in estimating this cell mass, because of the irregular distribution of the parenchymal cells. Histo- pathological evaluation of the parenchymal cell content therefore has to be based on examination of a large number of sections. This is possible with an objective method using an image analysing computer technique (2) or semiquanti- tatively by conventional ocular evaluation. Both these methods have their limi- tations, however, in that the image analysing computer is not available in many centres and the ocular evaluation requires great experience on the part of the examiner. A more suitable method for determining the parenchymal cell content of parathyroid glands is therefore greatly needed. As the two main glandular components, parenchymal and fat tissue, differ in density (according to the estimate of Gilmour and Martin ( 1 ) the respective densities are approximately 1.10 and 0.90 g/ml), it should be possible to use glandular density as an indirect measure of parenchymal cell content. This report presents a method for density determination of parathyroid glands, using values of weight and volume. The volumes of the glands were 255 measured in a sensitive volumeter. METHODS AND MATERIAL A volumeter was constructed according to the diagram in Fig. 1. Phosphate- buffered saline (0.1 M, pH 7.2, 300 mOsm/l) was used as the fluid in the volu- meter measurements. To represent the density of pure parenchymal cell tissue, pieces of histologically verified, fat-free, solid parathyroid adenomas were weighed and measured in the volumeter. The density of intraglandular fat tissue was calculated from measurements of small pieces of fat taken from the sur- roundings of the parathyroid glands. Volumes were determined as the mean of five A [ 0-J- gland in cylinder Fig. 1. Volumeter. In measuring the volume of the gland Archimedes' principle is applied. Part A of the apparatus can be disconnected when the gland to be measured is put in the cylin- der. Before disconnecting part A, the fluid is drawn below the cylin- der (to a') with the piston in or- der to keep the fluid in the system The connection B is a watertight, carefully ground glass-plate con- nection. When the gland is in the apparatus and the surface of the fluid is adjusted (to a), the other surface of the fluid column is moved from bo to bl. The volume of the capillary from bo to bl is the volume of the gland. consecutive measurements on the same piece of tissue. To prevent dehydration due to evaporation the pieces of tissue were kept in a moist chamber between measurements. The reproducibility of the volumeter technique was evaluated and the maximal deviation from the mean value in series of repeated measurements was 1 . 2 3 % . The volumeter technique was tested on ten parathyroid glands taken from autopsy cases within 24 hours after death. The glands were cleared of surround- ing fat and weighed, and their volume was estimated in the volumeter. After these measurements they were fixed in formalin and stained with hematocylin- -eosin, and the parenchymal cell content was evaluated by conventional light microscopy on 10-12 sections of each gland. 256 F i g . 2 . Diagram r e l a t i n g d e n s i t y o f p a r a t h y r o i d g l a n d s t o p a r - enchymal c e l l c o n t e n t . Parenchymal tissue The e f f e c t s upon t h e measurement r e s u l t s o f e v a p o r a t i o n due t o e x p o s u r e t o a i r between measurements were i n v e s t i g a t e d . RESULTS The d e n s i t i e s o f parenchymal and f a t t i s s u e were f o u n d t o be 1.059 * 0 . 0 0 5 g/ml ( n = 1 0 ) and 0 . 9 3 +_ 0 . 0 2 g/ml ( n = l o ) , r e s p e c t i v e l y . From t h e s e r e s u l t s t h e diagram i n F i g . 2 was c o n s t r u c t e d , t o r e l a t e t h e d e n s i t y of g l a n d s t o p a r - enchymal c e l l c o n t e n t i n p e r c e n t . The r e s u l t s o f t h e s e c a l c u l a t i o n s of t h e parenchymal c e l l c o n t e n t were i n a g r e e m e n t w i t h t h e f i n d i n g s a t l i g h t m i c r o s c o p y on 10-12 s e c t i o n s of e a c h g l a n d . Water loss d u e t o e v a p o r a t i o n of t i s s u e was found t o have a marked e f f e c t upon t h e measurements. The t o t a l w e i g h t of g l a n d s exposed t o t h e a i r f o r 15 min d e c r e a s e d by 10-15 % due t o w a t e r loss. T h i s w a t e r loss c o u l d b e minimized by k e e p i n g t h e tissues i n a moist chamber o r c o v e r e d w i t h a p i e c e of f a t t i s s u e be tween measurements . DISCUSSION I n t h i s s t u d y a v o l u m e t e r t e c h n i q u e was used t o estimate t h e d e n s i t y o f t h e t w o main t i s s u e components o f t h e p a r a t h y r o i d g l a n d - parenchymal and f a t t i s s u e . The d i f f e r e n c e i n d e n s i t y between them was pronounced ( 1 . 0 6 and 0 . 9 3 g / m l ) . From t h e s e v a l u e s d e n s i t i e s r e p r e s e n t i n g 100 % and 0 % parenchymal c e l l c o n t e n t were c a l c u l a t e d and a d i a g r a m was c o n s t r u c t e d whereby g l a n d u l a r d e n s i t y c o u l d be u s e d f o r e s t i m a t i o n o f t h e c o n t e n t of parenchymal c e l l s . V a l u e s ob- t a i n e d by t h e u s e o f t h i s diagram were i n agreement w i t h parenchymal c e l l con- t e n t s o b t a i n e d by a c o n v e n t i o n a l method, u s i n g l i g h t m i c r o s c o p y on 1 0 - 1 2 sec- t i o n s o f e a c h g l a n d . The d e s c r i b e d t e c h n i q u e i s a new way of e s t i m a t i n g t h e parenchymal c e l l mass o f t h e p a r a t h y r o i d s and is c o n s i d e r e d a u s e f u l advancement 257 in the histopathological characterization of these glands. The reproducibility of the volumeter measurements was good. However, effects of tissue evaporation necessitated procedures to prevent water loss. The volumeter technique is rapid compared to conventional histopathological methods for determination of the parathyroid parenchymal cell content. However, to get reproducible results measurements with the volumeter have to be made with great care, which makes them somewhat time-consuming. The method could be de- veloped further, however, by electronic reading and automatic adjustments of the volumeter pistons. With such improvement it could well be of value for intra- operative characterization of parathyroid glands. The density technique for histopathological evaluation of parathyroid glands has on basis of the preliminary results presented above now been further de- veloped using a more convenient and reproducible density gradient column tech- nique (3). ACKNOWLEDGEMENT This work was supported by a grant from the Swedish Medical Research Council, Project No. B77-17X-04787-02. REFERENCES 1. Gilrnour. J.R. & Martin, W . J . : The weight of the parathyroid glands. 2. Grimelius, L., Akerstrom, G., Johansson, H. Ei Lundqvist, H.: Estimation of J Pathol Bacteriol 44:431-462, 1937. parenchymal cell content of human parathyroid glands using the image ana- lysing computer technique. Am J Pathol 93:793-799, 1978. 3. Akerstrom, G., Grimelius, L., Johansson, H., Lundqvist, H. & Pertoft, H.: Estimation of the parenchymal cell content of parathyroid glands by means of density gradients. (To be published). Accepted January 15, 1979 Address for reprints: Goran Akerstrom, M.D. Department of Surgery University Hospital S-750 14 Uppsala Sweden 258