INTRODUCTION

Plastinated specimens were introduced to morphological disciplines more than twenty-five years ago and  have proven to be of great use (von Hagens et al., 1 987). They are dry and hygienic which  enables them  to be used in an everyday environment  (von Hagens  et  al.,  1985).  Our previous study  along with numerous others reported that both instructors and students have found plastinated specimens as useful supplements in the anatomy curriculum (Mansor,  1996; Alpar et al., 2001; Latorre et al., 2004; Lozanoff, 2004; Riederer et al., 2004 ; Serodio et al., 2004 ; Latorre et al., 2006).

Recently, we have broadened our activity in plastination to include pathological  specimens as have many institutions (Kularbkaew and Cook, 1996; Martin­ Alguacil and Martin-Orti, 2004).  More than one hundred specimens have been plastinated in the Department of Anatomy, Histology and Embryology for the Department of Pathology, Semmelweis University of Medicine. Preservation of pathologic specimens has produced new challenges.  Instead of  the fixation of healthy organs, pathologically transformed tissues  have to be preserved showing the characteristics which differ from those of normal tissues. Tumorous, inflamed, or degenerated tissues need to be plastinated with their typical surroundings preserved as well. In other cases, subtle color differences which were of primary importance in pathological diagnoses need to be retained.

Although plastinated specimens cannot replace the experience of dissection and the survey of fresh, unfixed organs, they can be used outside the dissection room. For this reason, they are useful supplements to student studies and in the preservation of precious rarities.

MATERIALS AND METHODS

In order to investigate the conservation of different types of diseased tissues, specimens destined for plastination were selected from a broad range of diseases. Specimens were fixed in 4% formalin for a minimum of three weeks.  Subsquently, they were dehydrated by freeze substitution with -25°C acetone. Four changes of acetone were carried out over an eight­ week period.  After dehydration,  specimens   were impregnated in a reaction-mixture of SR10 polymer (Biodur™) with l% Catalyst SH03 (Biodur™) . Vacuum was adjusted to a slow rising of bubbles in the silicone. Bubbles lasted four weeks. The specimens were returned to atmospheric pressure,  removed from the silicone bath, warmed to room temperature and prepared for curing with Gas Cure SH06 (Biodur™). In order to preserve the often rather vulnerable mutations, specimens were handled with care. Specimens were placed in a closed atmosphere, which was saturated by gas cure using an aquarium air pump working continuously for seven hours per day the first two days. Calcium chloride was used to control moisture in the curing chamber.  Specimens were wiped every two hours the first day. Thereafter they were kept in the container for seven days and wiped as needed .

RESULTS

Figure 1. Coronal section of human brain with blood filled lateral ventricles (A), longitudinal section through human heart and pericarial sac demonstrating cardiac tamponade with the causative lesion at arrow (B), longitudinal section of human descending aorta with ulcerated, hemorrhagic atherosclcrotic plaques at arrows (C), transverse section through human brain with intraparenchymal hemorrhage at arrows (D).

Hemorrhage

Although significantly different in  consistency, extensive brain hemorrhage which fully invaded the ventricles was plastinated preserving the typical location of the hemorrhage (Fig. l a). Similarly, pericardiac tamponade was also demonstrable along with the exact locus of the ventricular wall rupture (Fig. l b).  The  striking color of ulcerated, hemorrhagic atherosclerotic plaques was preserved after plastination in the wall of  the descending aorta  (Fig.  l e). Preservation of color  differences  aided  identifcation of intraparenchymal  bleedings in the brain caused by multiform glioblastoma (Fig. I d).

Tumors

The typical fine structure of the  tumor  was recognized on most specimens. The vortical, fibrous construction of an ovarian fibroma was visible (Fig. 2a) as was the spreading and osteolytic character of a bone metastasis (Fig. 2b).

Inflammation

Characteristic  features,  i .e. color or surface differences of inflamed tissues were preserved.  The typical multiple pin shaped and sized microabscesses of purulent pyelonephritis were  recognizable on the surface of the kidney (Fig. 3a). The yellow-green color of a purulent meningitis could also be demonstrated after plastination  (Fig. 3b).

Surface preservation

After plastination the characteristic fibrous, uneven surface of fibrinous pericarditis remained demonstrable (Fig. 4a). As well, erosions could also be observed on the mucosa of a metastatic infiltrated stomach (Fig. 4b).

Figure 2. Longitudinally sectioned human ovary with ovarian fibroma (A ), osteolytic metastasis in the epiphyseal region of a bone (B).

Figure 3. Plastinated kidney demonstrating purulent pyelonephritis (A). Plastinated brain (B) demonstrating purulent menengitis at arrows.

Figure 4. Subsinousal surface of plastinated human heart demonstrating fibrinous pericarditis (A), mural erosions (at arrows) in a metastatic infiltrated human heart ( B).

DISCUSSION

During the  last decade, the Department of Pathology at Semmel weis University of Medicine has collected a hundred specimens which represent outstanding examples of different pathological diseases or rarities in medicine. Tumors and other pathologies are fixed to healthy tissues which presents a challenge in collecting, as well as, preparing tissue for plastintion. In spite of these problems many pathological tissues have now been plastinated.

Numerous preparations of various diseases and organs were successfully plastinated which suggests that diverse types of pathological  tissues can be properly conserved by this method. The present study offers insight into the possibilities in the plastination of pathological specimens. A great challange in preserving these specimens by plastination is the preservation of small, but diagnostically important colors and textures of the tissues.

Subtle changes on the surface of organs remained demonstrable irrespective of the kind of the mutation; degenerative (Fig. le), tumorous (Fig. 2b) and inflammatory (Fig. 3a) changes were equally recognizable. The inner structure of various diseased tissues could also be studied on the cut surface of the organ, typically in tumors which enabled the observer to identify both the type and the extension or demarcation.

Color differences are of primary importance in pathological diagnostics which can be properly studied only on fresh and unfixed specimens.  On  most plastinated preparates, the true colors were faded. This was due to formalin fixation and dehydraton but not to the silicone plastination process. Nevetherless, typical color differences could be properly demonstrated on numerous specimens (Figs. I a, I c, 3b).

Diagnostics also depend upon recognition of alterations in the consistency of the diseased tissue. This helpful feature is completely lost when the organ is plastinated which much be acknowledged as an inevitable shortcoming of the method.  It has to be mentioned, however, that the consistency of both health and tumorous or degenerative tissues is changed during formalin fixation as well.

Fixation of non-stable tissues, e.g. bleeding  (or hemhorrage) is another problem to be solved. In addition to the risk that the hemorrhage could be easily washed out, its shrinkage is different from that of the surrounding tissues.  Still,  hemorrhages could be plastinated in loco on severa l specimens (Fig. 1 A-C).

Considering the large number and variety of plastinated specimens, we suggest that plastination can be usefully applied in the conservation of pathological tissues.

Acknow ledgements

We would like to thank M. Toth and L. Patonay for the quality photos.