METHOD OF IMPREGNATING A TISSUE SPECIMEN WITH PARAFFIN

Abstract: In a method of impregnating a tissue specimen with paraffin either directly after an optional treatment of the tissue specimen with a fixing agent or after the tissue specimen optionally has been treated with a fixing agent and/or a dehydrating agent an immersion of the tissue specimen into a bath of liquid paraffin takes place. The bath is kept below a predetermined temperature at which thermolabile components and properties of the tissue specimen undergo changes. The pressure of the bath is then lowered from atmospheric pressure to a predetermined pressure at which water present in the tissue specimen and/or, when appropriate, the dehydrating agent vaporizes, the pressure of the bath then being increased again to atmospheric pressure.

Description: Method of impregnating a tissue specimen with paraffin. TECHNICAL FIELD The invention refers to a method of impregnating a tissue specimen with paraffin. BACKGROUND ART Such methods are known from GB 1 536 422 and GB-A- 2 065 9 In both these known methods the tissue specimens are trea with a dehydrating agent, alcohol and acetone, respective before the tissue specimens are immersed in a bath of liquid paraffin. After the tissue specimens have been immersed in the paraffin bath, the pressure of the bath is lowered so muc that the respective dehydrating agent is vaporized and thereby evaporates from the tissue specimens as well-as from the paraffin bath, the pressure of the bath then being increased again to atmospheric pressure. From GB 1 536 422 it is apparent that the operating temperature is 65 C, while no temperature information can be found in GB-A-2 065 912. However, it could be assumed that the operating temperature also in the last mentioned case is about 60-65 C. However, it has been found that a temperature higher ' .than about 45-47 C destroys the structure of the tissue specimens and also has a shrivelling effect on the tissue i has also been found that proteins and other thermolabi tissue components as well as thermolabile properties are changed at higher temperature in such a way that antigen structures cannot be recognized to a sufficient extent in a subsequent histochemical tissue diagnosis. Moreover, membranes and organelles become shrivelled and are destroyed. DISCLOSURE OF INVENTION An object of the invention is to provide a method of impregnation that eliminates the disadvantages of the methods known hitherto. Another object of the invention is to provide a method of impregnation in which the treatment with a dehydrating agent can be eliminated. This is attained by the method according to the invention in that the tissue specimen is immersed, either directly after an optional treatment of the tissue specimen with a fixing agent or after the tissue specimen optionally has been treated with a fixing agent and/or a dehydrating agent, in a bath of liquid paraffin which is kept below a predetermined temperature at which thermolabile component and properties of the tissue specimen undergo changes, and that thereafter, the pressure of the bath is lowered from atmospheric pressure to a predetermined pressure, at which water and/or, when appropriate, the dehydrating agent vaporizes. Then the pressure of the bath is increased again to atmospheric pressure. PREFERRED EMBODIMENTS When carrying out a histochemical diagnosis, normally a tissue specimen is first treated with a fixing agent, usually formalin, and thereafter with a dehydrating agent, e.g. methanol, ethanol or acetone, before the tissue specimen is immersed in a bath of liquid paraffin. In this bath the tissue specimen is impregnated with paraffin. The tissue specimen impregnated in this way with paraffin is then embedded in a paraffin block which can be cut by means of a microtome knife to obtain thin cuts (1-5 urn thic which can thereafter be examined in a microscope after the paraffin has been removed and after dyeing. According to the invention it is suggested that after an optional treatment of the tissue specimen with a fixing agent, the tissue specimen is directly immersed into the paraffin bath. For this bath a paraffin having a melting point of about 37-44 C has been chosen and the bath is kept at a temperature of about 47 C at the most, i.e. below the temperature at which it has been observed that thermolabile components and properties of the tissue specimen begin to change. It should be pointed out that this temperature can vary somewhat depending on which type of tissue specimen one wants to examine. According to the invention the pressure of the paraffin bath is thereafter lowered from atmospheric pressure to at least about 76 mm Hg, i.e. the pressure at which water boils at a temperature of about 46 C. In this way, water present in the tissue specimen will vaporize and evaporate from the tissue specimen as well as from the paraffin bath. Then, the pressure of the bath is increased again to atomospheric pressure. The lowering of the pressure as well as the pressure increase must not take place too abrupt. The tissue material and cells present therein can burst through sudden pressure changes during the pressure lowering phase and can be compressed during the pressure increasing phase. According to another embodiment of the invention the tissue specimen can also be treated with a dehydrating agent, for example methanol, ethanol or acetone, before the sample is immersed into the paraffin bath which also in this case is kept below the temperature at which thermolabile components and properties of the tissue specimen are changed. When acetone is used as a dehydrating agent, the pressure of the paraffin bath has to be lowered to at least about 510 mm Hg, i.e» the pressure at which acetone vaporizes at a temperature of about 45 C. Thus, the acetone will vaporize and evaporate from the tissue specimen as well as from the paraffin bath. To ensure that any remaining water also will evaporate from the tissue specimen, the pressure of the bath must also in this case be lowered to at least 76 mm Hg. By the paraffin impregnating method according to the invention it has been found that the quality of the tissue specimens is improved compared to paraffin impregnating methods known hitherto.

Claims: CLAIMS 1. Method of impregnating a tissue specimen with paraffin, characterized in that either directly after an optional treatment of the tissue specimen with a fixing agent or after the tissue specimen optionally has been treated with a fixing agent and/or a dehydrating agent, the tissue specimen is immersed in a bath of liquid paraffin which is kept below a predetermined temperature at which thermolabile components and properties of the tissue specimen undergo changes, that the pressure of the bath is then lowered from atmospheric pressure to a predetermined pressure at-which water present in the tissue specimen and/or, when appropriate, the dehydrating agent vaporizes, whereupon the pressure of the bath is increased to atmospheric pressure. 2. Method according to claim 1, characterized in that the temperature of the bath is kept at about 47 C at the most. 3. Method according to claim 1, characterized in that the pressure of the bath is lowered to at least about 510 mm Hg. 4. Method according to claim 3, characterized in that the pressure of the bath is lowered to at least about 76 mm Hg.

Inventors: RENVALL HENRIK GERHARD, RENVALL, HENRIK, GERHARD
Applicants: RENVALL HENRIK GERHARD, RENVALL, HENRIK, GERHARD
Application year: 1986
Main classification: G01N1
IPC codes: G01N1