WO1995014221A1

WO1995014221A1 - Processing cassette for tissue samples

Info

Publication number: WO1995014221A1
Application number: PCT/AU1994/000715
Authority: WO
Inventors: Gregory Milton Muir
Original assignee: Ramsay Hospital Holdings Pty. Ltd.
Priority date: 1993-11-18
Filing date: 1994-11-18
Publication date: 1995-05-26

Abstract

A tissue specimen processing cassette (11) having a casing (13) with a chamber (15) therein. The chamber (15) has a platform (19) on which tissue samples may be placed, and a plurality of apertures (23) extending therethrough which allow fluid to pass from the chamber (15) to the space (25) below the platform (19). The chamber (15) is covered and sealed by a cap (27), and the casing (13) is covered and sealed below the platform by a cap (29). The platform (19) has a downwardly extending skirt (35), and is supported within a sleeve member (37) for sliding movement relative thereto. The sleeve member (37) has a plurality of apertures (55) for exchange of fluids, and is telescopically slidable within the casing (13), so as to extend outside the casing to expose the apertures (55), so fluids can be exchanged from the chamber (15) to outside the casing, when processing a tissue sample. With the sleeve member (37) unextended and the apertures (55) retained within the casing (13), the cap (29) may be removed to embed a tissue sample contained in the chamber (15) in wax. While the wax is molten, the platform (19) may be slid toward the cap (27), to ensure that the tissue sample lies proximal to the cap (27).

Description

"PROCESSING CASSETTE FOR TISSUE SAMPLES"

This invention relates to the field of tissue biopsy and histological assessment. Particularly the invention relates to the handling of samples for biopsy or histological assessment and an apparatus for handling 5 tissue specimens from collection to embedding and microtome or other sectioning.

Hitherto in the collection of tissue specimens for biopsy, jars have been used to contain the tissue specimen at the point of collection. These jars typically are of plastic

10 construction, generally having a capacity of around 70ml, and are provided with a screw fitting lid which may sealingly engage thereto. These jars may be suitable for containing larger specimens, but where the sample size is small, such as around 3mm diameter as is typical with

15 current specimen collection procedures, handling difficulties become apparent. Particularly, due to the large size of the jars, the amount of formaldehyde fixative used is guite high in each case.

With present surgical treatment technigues, numbers of 20 specimens of 3mm diameter or less are collected from the gastro-intestinal tract, lung, bladder and other body sites for histological assessment. This move towards small samples has arisen from the involvement of fibre optics in medical instruments. However no matching development has ²⁵ occurred in the laboratory to efficiently handle small specimens which do not require orientation before sectioning.

Φ Current procedures for handling smaller tissue specimens have evolved from the techniques established to handle

30 large tissue pieces, and require handling each tissue fragment with forceps at least twice. These techniques impose a high risk of damage and loss while resource and time use is high.

The process for dealing with specimens has involved placing them in a fixative such as formaldehyde, whereupon they are sent to the laboratory for further processing. Further processing may involve a procedure where the specimens are immersed sequentially in ethyl alcohol, then chloroform, which results in replacement of aqueous tissue fluids with organic solvents, before immersion in molten paraffin wax, which displaces the organic solvents. When the paraffin wax is set, the specimens may be sampled, by any convenient method such as microtome, whereafter the sections may be examined.

With the advent of small tissue specimens, a system involving use of a plastic cassette to contain the specimens during the above process has been utilised. Typically these cassettes consist of a shallow box with a lid which may be closed. The lid positively locks in the closed position, containing the samples within the closed cassette. Both the lid and base of the cassette -are open mesh components having vents to permit exchange of fluids therethrough for processing the specimen. The cassettes are made from plastic which will withstand prolonged exposure to solvents without distortion. These cassettes often require an insert of additional containment for material of smaller size than the vent openings of the cassette, especially where the sample size is small enough to fit through the vent openings. Such additional containment may be porous polyurethane foam, paper or very fine metal mesh.

The cassette also conveniently includes a surface for attaching or writing identification of the sample for tracking through the processing procedure. The current procedure for small samples, in the order of 3mm diameter or less is as follows. The cassette is supplied in one piece, with the lid open, exposing the box interior.

The identification of the specimen is recorded on the external surface of the cassette in pencil, on a portion of the surface roughened to accept markings from a pencil.

Then a piece of polyurethane foam having an area commensurate with the base of the box and being 2mm to 3mm thick, is placed inside the box so as to overlie the vents in the base. The tissue specimens are placed on the foam, and a further like piece of polyurethane foam is placed over the tissue specimens. The lid of the cassette is then closed, to retain the polyurethane foam pieces and the tissue specimens inside the box. The closed cassette is then placed in a jar of the type described above containing fixative, whereinafter it is transported for further treatment to process the specimens for embedding in paraffin wax.

p_or the embedding procedure, the processed tissue specimens are removed from the cassette using forceps and placed in an embedding tray, containing paraffin wax which is maintained at a temperature sufficient to maintain the paraffin wax in a molten state. The portion of the cassette with the markings identifying the specimen is placed over the embedding tray, and molten paraffin wax is poured over the embedding tray. When the wax is cool the portion of the cassette and the specimens are encapsulated in the solidified wax, which is separated from the embedding tray for microtome.

The procedure discussed above has a disadvantage insofar as that it necessitates excessive handling of the tissue specimens. Furthermore, it remains necessary to use a discrete vessel to fix the tissue specimens, and to perform the processing steps prior to embedding in paraffin wax.

In accordance with one aspect of the present invention there is provided a cassette for tissue specimen processing comprising a casing having a chamber therein for containing said specimen, said chamber having a platform located therein for placement of said specimen thereon, said casing having a first removable closure for covering said chamber and removeable to provide access to said platform and said chamber, and having a second removable closure for covering said chamber and removeable to provide access to said chamber underneath said platform.

With such an arrangement it is possible to treat and process the specimen through to being ready for analysis without having to remove the specimen from the cassette.

Preferably said first removable closure sealingly covers said chamber.

Preferably said second removable closure sealingly engages said casing to prevent egress of fluid from said chamber.

Preferably said platform defines with said chamber, means for selectively allowing egress of fluid.

Preferably said platform has a plurality of apertures to allow egress of fluid between the upper surface thereof and underneath said platform.

In this manner, when the first and second removable closures are removed, the specimens may be flushed, when the second removable closure is in place, the specimen may be immersed. Preferably said casing includes a sleeve member for supporting said platform for sliding movement therein, to vary the volume of the portion of chamber above said platform. Movement of the platform along the sleeve member results in variation of the volume of the portion of the chamber above the platform.

Preferably said sleeve member is arranged for telescoping movement within said casing, between a raised position in which said platform is presented away from said casing, and a lowered position. In the raised position, a processed specimen may be conveniently presented for microtome.

Preferably said platform is slidably moveable to and from a depressed position in which the volume of the portion of chamber is minimised.

Preferably said means for selectively allowing egress of fluid includes a plurality of vents arranged around the upper portion of said sleeve, said vents being arranged to be sealingly occluded when said platform is in said depressed position.

Preferably said plurality of vents are also arranged to be occluded when said sleeve is in said lowered position. In this manner, there may only be free exchange of fluids through said vents when said sleeve is in said lowered position and said platform is moved away from said depressed position.

Preferably said platform includes sealing means for sealing against said vents in said depressed position.

Preferably said sealing means includes a skirt extending beneath and around the periphery of said platform, arranged to sealingly engage against the internal walls of said sleeve.

Preferably said first removable closure sealingly engages to said sleeve member.

Preferably said sleeve member is arranged to provide a fluid tight seal with said casing.

Preferably said sleeve member includes a circumscribing line of weakness to allow a part of said sleeve to be broken away to expose the portion.

Preferably said line of weakness is located in proximity to said vents.

The invention will now be described with reference to the following description of one specific embodiment thereof, in which:-

Figure 1 is a cross section view of the tissue processing cassette, showing the cassette - in a convenient "as supplied" condition;

Figure 2 is a cutaway perspective view of the cassette shown in figure 1;

Figure 3 is a cross section of the cassette showing the sleeve member in the raised position;

Figure 4 is a cutaway perspective view of the cassette shown in figure 3;

Figure 5 is a cross section of the cassette showing the sleeve member in the raised position and the platform in the depressed position; Figure 6 is a cutaway perspective view of the cassette shown in figure 5;

Figure 7 is a cross section of the cassette showing a specimen ready for microtome;

Figure 8 is a perspective view of the platform for the cassette;

Figure 9 is a perspective view of the sleeve for the cassette; and

Figure 10 is a perspective view of the cassette shown in figure 1.

Referring to figures 1 to 6 and 10 of the drawings, the tissue specimen processing cassette, indicated generally at 11, has a casing 13 having a chamber 15. The chamber 15 is defined by upstanding walls 17 which extend completely therearound. While the cassette 11 is only shown in part, in the cutaway perspective views in figures 2, 4 and 6, the cassette 11 is shown in full in figure 10.

The chamber has a platform 19 on which tissue samples may be placed. The platform 19 includes an upwardly extending lip 21; and a plurality of apertures 23 extending therethrough which allow fluid to pass from the chamber 15 to the space 25 below the platform 19.

The cassette 11 includes a first removable closure in the form of a cap 27 for providing access to the chamber 15, and a second removable closure in the form of a cap 29 for providing access to the space 25 underneath the platform 19. The caps 27 and 29 each have an inwardly extending annulus 31 which are each arranged to mate in interlocking arrangement with externally extending annuli located on the cassette 11, in such a manner that an interlock is formed for positive retention of the caps 27 and 29 to the cassette 11. Furthermore, when fitted to the cassette 11, the caps 27 and 29 form a fluid tight seal therewith.

The platform 19, also shown in greater detail in figure 8, has a downwardly extending skirt 35. The platform 19 is supported within a sleeve member 37, its downwardly extending skirt 35 facilitating stable alignment of the platform 19 within the sleeve member 37, to facilitate sliding movement therealong.

In use, tissue specimens are placed in the chamber 15 above the platform 19. The platform 19 may be moved to a depressed position, to minimise the volume of the chamber 15 above the platform 19, and to pin a tissue sample or tissue samples against the cap 27, to locate all tissue samples in the same plane and present them outermost for later microtome. This may be achieved by removing the cap 29, and manipulating the platform 19 by its central spigot 39, to move it to the depressed position. If orientation of the tissue specimen is important, then the platform 19 may be removed, in order to give access to the chamber 15, and allow the tissue specimen to be orientated, before the platform 19 is replaced. In its most preferred use, the cap 27 of the cassette 11 is removed, and the tissue specimen or tissue specimens are placed in the chamber 15, on the platform 19, in the reguired orientation if necessary. A fixative fluid such as formaldehyde is poured into the chamber 15 so as to immerse the tissue specimen, whereafter the cap 27 is replaced, and the cassette 11 containing the sample and the fixative may be forwarded to the laboratory for further processing.

Extending away from the casing 13 is a plate portion 41 having an inclined portion 43. The plate portion 41 is provided merely for handling purposes, as the volume of the chamber 15 and the space 25 below the platform 19 combined, is in the order of 12mm x 12mm x 12mm, as shown in figures 1 and 2, the cassette 11 being shown in figure 1 at approximately five times its actual size. The inclined portion 43 of the cassette 11 has a surface with a roughened texture, so as to accept pencil lead markings, so that the identification of the tissue specimen contained within the chamber 15 may be recorded for later reference.

Referring to figure 9, the sleeve member 37 is shown in greater detail. Immediately below the externally extending annulus 33 is an outwardly extending rib 45 spaced in parallel relationship with the external extending annulus 33 so as to define a groove 47 therebetween. Referring to figure 1, the casing 13 has an inwardly extending annulus 49 extending therearound. The groove 47 in the sleeve member 37 is sufficiently wide to accept both the inwardly extending annulus 31 of the cap 27 and the inwardly extending annulus 49 of the sleeve member 37, so as to positively retain these parts in the interlocked condition shown in figures 1 and 2.

Referring again to figure 9, the sleeve member 37 includes a further externally extending rib 51, located approximately two thirds along its body. At the base of the sleeve member 37 is an annular step 53 extending therearound. Located around the upper periphery of the sleeve member 37 are a number of vents 55 which extend through the wall of the sleeve member 37, so as to permit the exchange of fluids, as will be understood from the description which follows.

Referring to figures 1 and 3, the sleeve member 37 may be moved between a lowered position as shown in figure 1, to a raised position as shown in figure 3. The further externally extending rib 51 of the sleeve member 37 positively interlocks with the inwardly extending annulus 49 of the casing 13, to lock the sleeve member 37 in the raised position.

The annular step 53 abuts a complementary shaped portion 54 of the casing 13, to limit the outward extent of movement of the sleeve member 37 with respect to the casing 13 of the tissue specimen processing cassette 11.

In the raised position, the vents 55 of the sleeve member are exposed, and the fixative may be drained therethrough. Before the tissue sample is subjected to further processing, the cap 29 should be removed from the base of the casing 13, so as to permit fluid flow through both the vents 55 of the sleeve member 37 and the apertures 23 in the platform 19. The cassette 11 containing the tissue specimen or specimens may be then immersed sequentially in ethanol, and then chloroform. The cassette 11 should be subjected to fluids immersion in the normal manner that tissue samples have previously been processed. In this fluid processing step, the fluids may easily -flow and disperse through the vents 55 and the apertures 23. The plate portion 41 of the casing 13 is provided with vents 57 to further assist with flow and dispersal of the fluids during this step.

As a final step in the embedding procedure, the cassette 11 containing the tissue specimen or specimens is inverted so that the cap 27 is lowermost, whereafter a small amount of molten paraffin wax is poured into the space 25 below the platform 19, so as to percolate through the apertures 23 in the platform, and around the issue specimen, up to the vents 55. While the paraffin wax remains molten the platform is pushed to the depressed position by its central spigot 39, as shown in figures 5 and 6. In this position, - l i ¬

the downwardly extending skirt 35 of the platform 19 occludes the vents 55 of the sleeve member 37, to prevent outflow of molten wax therethrough. The wax is topped up to a level to cover all moving parts, via the space 25 beneath the platform 19, while the cassette 11 remains inverted with its cap 27 lowermost. The cassette 11 is retained in this position, while the wax solidifies, providing rigid support for microtome.

Once the wax has solidified, the cap 27 is removed to expose the tissue specimen or specimens embedded in the wax. A line of weakness 59 is included in the sleeve member 27, extending between the externally extending rib 45, and that portion of the sleeve member 37 planar with the upper most vent 55a. The line of weakness 59 extends around the sleeve member 37, and enables that portion of the sleeve member 37 containing the externally extending annulus 33 and the externally extending rib 45, to be peeled away from the remainder of the sleeve member 37, to expose the sides 60 of the wax 61 containing the embedded tissue specimen or specimens 63, as shown in figure 7. At this stage, the embedded specimens may be subjected to microtome or otherwise sectioned, for pathological analysis.

Depending on the plastics material utilised, it may be necessary to provide a line of weakness extending upward toward the cap 27, to enable the start of the peeling of the portion.

The plate portion 41 of the casing 13 serves as a convenient holder for the specimens during the microtome step, and as will be apparent, lends itself to being fitted to a jig₇ for holding during the microtome or sectioning process. It will be understood that the cassette should be sufficiently strong or reinforced to withstand any clamping forces it may be subjected to at this stage.

As will readily be apparent, the embodiment of the invention described above has significant advantages over the prior art. Particularly, it obviates the need to use the disposable plastic jar which is used to contain the specimen and formaldehyde fixative, or the specimen and the previously known processing cassette and formaldehyde fixative, while in transit from the clinic or theatre to the laboratory. Furthermore, it minimises the handling, particularly obviating the need to handle the tissue with forceps, except where the tissue specimen must be orientated in a particular manner prior to embedding. The specimen processing cassette according to the invention also eliminates the need to use a separate embedding tray, which eliminates the need for handling the tissue specimen at the end of the processing cycle, prior to embedding the specimen with wax.

It should be understood that variations may be made to the embodiment described, for example to enable handling of larger specimens the size of the casing may be increased to include the area occupied by the plate portion 41 of the embodiment, with appropriate adjustments being made to the size of the sleeve member, platform, and caps.

Furthermore, additional vents may be included around the chamber, for example in the upstanding walls 17, to allow fluid processing while the platform 19 is away from the depressed position, and the sleeve member 37 is in the lowered position, as shown in figures 1 and 2.

For convenience a tear off tag may be included to support a label for use by the person collecting the specimens. In this manner, the labelling of the cassette could be left to the technicians, at the stage when the tissue is about to be processed in the laboratory.

It should be understood that the scope of the invention is not limited by the embodiment described herein.

Claims

THE CLAIMS defining the invention are as follows:-

1. A cassette for tissue specimen processing comprising a casing having a chamber therein for containing said specimen, said chamber having a platform located therein for placement of said specimen thereon, said casing having a first removable closure for covering said chamber and removeable to provide access to said platform and said chamber, and having a second removable closure for covering said chamber and removeable to provide access to said chamber underneath said platform.

2. A cassette as claimed in claim 1 wherein said first removable closure sealingly covers said chamber.

3. A cassette as claimed in claim 1 or 2 wherein said second removable closure sealingly engages said casing to prevent egress of fluid from said chamber.

4. A cassette as claimed in any one of the preceding claims wherein said platform has a plurality of apertures to allow egress of fluid between the upper surface " thereof and underneath said platform.

5. A cassette as claimed in any one of the preceding claims wherein said casing includes a sleeve member for supporting said platform for sliding movement therein, to vary the volume of the portion of chamber above said platform.

6. A cassette as claimed in claim 5 wherein said platform is slidably moveable to and from a depressed position in which the volume of the portion of chamber is minimised.

7. A cassette as claimed in claim 5 or 6 wherein said sleeve member is arranged for telescoping movement within said casing, between a raised position in which said platform is presented away from said casing, and a lowered position.

8. A cassette as claimed in any one of the preceding claims wherein said platform defines with said chamber, means for selectively allowing egress of fluid.

9. A cassette as claimed in claim 8 wherein said means for selectively allowing egress of fluid includes a plurality of vents arranged around the upper portion of said sleeve, said vents being arranged to be sealingly occluded when said platform is in said depressed position.

10. A cassette as claimed in claim 9 wherein said plurality of vents are also arranged to be occluded when said sleeve is in said lowered position. In this manner, there may only be free exchange of fluids through said vents when said sleeve is in said lowered position and said platform is moved away from said depressed position.

11. A cassette as claimed in claim 9 or 10 wherein said platform includes sealing means for sealing against said vents in said depressed position.

12. A cassette as claimed in claim 11 wherein said sealing means includes a skirt extending beneath and around the periphery of said platform, arranged to sealingly engage against the internal walls of said sleeve.

13. A cassette as claimed in any one of claims 5 to 12 wherein said first removable closure sealingly engages to said sleeve member.

14. A cassette as claimed in any one of claims 5 to 13 wherein said sleeve member is arranged to provide a fluid tight seal with said casing.

15. A cassette as claimed in any one of claims 5 to 14 wherein said sleeve member includes a circumscribing line of weakness to allow a part of said sleeve to be broken away to expose the portion.

16. A cassette as claimed in claim 15 wherein said line of weakness is located in proximity to said vents.

17. A cassette substantially as herein described with reference to the description of the embodiment.