Abstract:
An apparatus for forming an amorphous tissue specimen into a cooled block while preserving the anatomical orientation of the specimen includes a base assembly, a system of magnetic movable wall units and a cover which may be intercoupled to form an enclosed specimen cavity. The wall units each include a hinged panel at one end, so that the wall units may be adjustably intercoupled to form various planar surfaced shapes, such as a rhomboid or eccentric block form. Each wall unit also includes a reservoir for a refrigerant such as liquid nitrogen for cooling the enclosed specimen to an optimal temperature for tissue cutting. The base is equipped with orientation indicia and temperature sensors. A synthetic resin may be applied to the specimen-contacting surfaces of the form in order to facilitate release of the cooled specimen. The invention provides a greatly improved method for rapid harvesting of the entire margin surface area a tumor to allow medical personnel to determine if any malignant tumor cells exist on the specimen margins.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is broadly concerned with an apparatus and method for forming, quick freezing and harvesting tissue from the margins of a tumor specimen, while preserving the anatomical orientation of the specimen. More particularly, it is concerned with an apparatus having a base, movable walls and a cover which may be adjustably intercoupled to frame a form for receiving and shaping an amorphous tissue specimen into a planar-surfaced block. The device further includes structure for freezing the specimen to a predetermined optimum temperature, so that the specimen will retain its shape for cutting after the form is removed. 
     Biopsy, or surgical removal of a tissue specimen for histologic examination, is frequently employed in order to establish a precise diagnosis. When a lesion is known or suspected to be malignant, the entire mass is typically excised, if possible, and an examination technique is often employed in which the tumor margin surface area is examined. This technique involves microscopic screening of the exterior surface area of the tumor for the presence of malignant cells to ensure that all such cells have been removed. If practiced effectively, tumor margin surface area examination enhances the likelihood of complete removal of all cancerous cells of a localized malignancy. Where removal of the malignancy was not complete, the method may be used to precisely identify the location of any residual malignancy for subsequent removal or, where that is not possible, for radiation therapy. 
     Once harvested, the tissue is frozen using, for example, the methods and devices set forth in Applicant&#39;s previous U.S. Pat. Nos. 4,695,339; 4,752,347; 5,628,197; 5,829,256; and 6,094,923, which patents are incorporated herein by reference, and the tissue is then sectioned into thin layers. The tissue is preferably snap frozen at a controlled rate in order to obtain a high quality frozen section which is not marred by voids and artifacts which might impair examination and diagnosis. Following dissection from the tumor, the tissue margin surfaces may also be further examined by methods such as electron microscopy. 
     In order to be effective, the technique of tumor margin surface area examination must include microscopic examination of the entire surface margin of the excised tumor. Moreover, the anatomical orientation of the tissue must be maintained throughout the procedure so that the surgeon may return to a specific source area of the tumor margin surface in order to excise additional tissue until histologic examination indicates that only healthy cells remain. 
     One of the problems associated with preparation of specimens for this method of histologic examination is that the tissue is normally excised in irregular shapes. Many tumors, such as breast cancer, are amorphous because they are comprised of fatty tissue. Anatomical orientation of the specimen is difficult to maintain when sectioning such specimens that are obtained, for example, in a lumpectomy for breast cancer. 
     It is difficult to conduct a thorough examination of the tumor margin surfaces in all planes because of the irregular geometric shape of such tumors. For example, a thin, planar surface slice of a round mass only effects a very small area of the total surface. That is, each thin section obtained by conventional methods from a tumor mass reveals only a portion of the tumor margin. However, the number of sections which can be examined microscopically is limited by practical considerations, such as time and availability of equipment and it is very difficult to orientate the excision position from an area where a large number of specimens were obtained. 
     It is important that the histologic examination be performed quickly, since the patient must be kept under anesthesia pending the microscopic evaluation, in case any additional tissue must be excised. For this reason, it is normally not possible to process large numbers of tumor margin surface sections in an effort to perform a completely thorough pathologic examination. 
     In order to obtain slices from the entire tumor margin surface area, it has been found to be expedient to form the tissue specimen into a polyhedron block having plane surfaces. Harvesting of the tissue from all of the resulting planar surfaces of the block serves to ensure that the entire tumor margin surface area has been harvested for examination. Because the block presents a limited number of such plane surfaces (six), the procedure can be conducted fairly quickly. 
     While it is important to form the entire excised tumor mass into a block, not all tumor masses are of the same size or shape, and many do not present bilateral symmetry. Although some tumor masses can be formed into a cube-shaped block having right angles or a rhomboid block having opposed complementary acute and obtuse angles at the vertices, there is a need for a form which can be adjusted to accommodate eccentric masses, which may lack parallel sides and angular symmetry. 
     In order to speed the examination process, the specimen must be quickly frozen to a predetermined temperature which will permit the tissue to retain a structured form. The specimen must then be promptly released from the form for harvesting of the tumor margin surfaces. 
     The apparatus and method of the present invention are specifically designed to quickly form and freeze an amorphous or eccentric specimen into a shape having a limited number of planar surfaces which are easily sectioned for rapid microscopic evaluation of the entire tumor margin. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an apparatus and method for forming an amorphous tissue specimen into a chilled block with generally planar surfaces, while preserving the anatomical orientation of the specimen. The invention provides a greatly improved method for rapid harvesting of the entire margin surface area of a tumor. The apparatus has a base supporting a system of movable wall units that are at least partially magnetic and a cover which are intercoupled, especially by magnetic attraction, to form a horizontally enclosed specimen cavity. The wall units each include a hinged panel at one end, so that they may be adjustably magnetically intercoupled to form a rhomboid or eccentric block form. Each wall unit also includes a reservoir for a cryogenic, liquid such as liquid nitrogen, for cooling the enclosed specimen to an optimal temperature for tissue cutting. The base is equipped with orientation indicia and temperature sensors. A synthetic resin coating may be applied to the specimen-contacting surfaces of the form in order to facilitate release of the chilled specimen. 
     OBJECTS AND ADVANTAGES OF THE INVENTION 
     The principal objects of the present invention are to provide a method and apparatus for forming a tissue specimen; to provide such a method and apparatus for forming an amorphous tissue specimen into a tissue block having planar surfaces; to provide such a method and apparatus for forming a tissue block having a limited number of planar surfaces which may be easily and quickly sectioned by a knife or other cutting instrument; to provide such a method and apparatus which maintain the anatomical orientation of a tissue specimen obtained by surgical excision; to provide such a method and apparatus which quick freeze the specimen to a predetermined temperature; to provide such a method and apparatus which permit rapid harvesting of tissue from the entire margin surface area of a tumor; to provide such an apparatus having magnetic wall units which may be adjusted in relative position to form a tissue specimen into a block; to provide such an apparatus having a magnetic base for supporting magnetic wall units in place; to provide such an apparatus having hinged wall units; to provide such an apparatus wherein the wall units each include a reservoir for holding a cryogenic liquid; to provide such an apparatus including a temperature indicator device; to provide such an apparatus having a base including a trough for collecting excess cryogenic liquid; to provide such an apparatus having walls and a base coated with a non-stick or easy release coating; to provide a method for using such an apparatus to form a surgically excised tissue specimen into a block, while retaining its anatomical orientation, cooling the specimen to an optimal freezing temperature, releasing the specimen, cutting a slice from each of the planar surfaces of the block, microscopically examining the slices for malignant cells, and excising additional specimens from a patient; providing such an apparatus and method which are relatively easy to use, inexpensive to produce and particularly well-suited for their intended usage. 
     Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of the invention. 
     The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a specimen preparation apparatus in accordance with the present invention, showing a tissue specimen in place with the cover unit removed. 
     FIG. 2 is a perspective view of a single wall unit of the specimen preparation apparatus, illustrating a hinged panel in an extended position. 
     FIG. 3 is a perspective view of a partial frozen tissue block formed in the apparatus of FIG. 6, and illustrating harvesting of a formed, planar tissue margin surface by slicing with a heated knife. 
     FIG. 4 is an exploded perspective view of the apparatus of FIG. 1, including multiple wall units having hinged panels and showing a magnetic insert removed from a reservoir of one of the wall units, the cover unit, a base platform, a base plate and a tray with portions removed to show detail thereof. 
     FIG. 5 is a top plan view of a second embodiment of the apparatus of FIG. 1, illustrating the use of high-Gauss permanent magnet. 
     FIG. 6 is a perspective view of a third embodiment of a specimen preparation apparatus employed for forming a rectangular or cube-shaped block of tissue. 
     FIG. 7 is a top plan view of the apparatus of FIG. 6, illustrating a tissue specimen in place in the apparatus and depicting movement of the wall units into position surrounding the specimen. 
     FIG. 8 is a top plan view of the apparatus of FIG. 6, illustrating the wall units in a tissue receiving configuration and engaging the surfaces of a tissue specimen. 
     FIG. 9 is a partially exploded perspective view of the apparatus of FIG. 6, illustrating a specimen cover unit. 
     FIG. 10 is a perspective view of the apparatus of FIG. 6, illustrating a tissue specimen engaged in a specimen compartment and an operator pouring liquid nitrogen onto the apparatus to cool the specimen. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. 
     I. Variable Shape Specimen Block-Forming Apparatus 
     Referring now to the drawing, a specimen preparation apparatus  1  for forming a tissue specimen  2  into various planar sided shapes such as the illustrated rhomboid or diamond shaped block  3  in accordance with the invention broadly includes a base assembly  4  supporting a form assembly  5  and a cover unit  6 . Each of these elements is constructed so that when intercoupled, they cooperatively define a generally enclosed, specimen-receiving compartment  7  having planar surfaces for engaging the outer surface of a spherical or odd shaped specimen  2  and forming the specimen into a block  3  with planar sides. The resulting block  3  is often rectangular or square in cross section; however, the block  3  may have other shapes including, but not limited to, shapes having a diamond, trapezoidal, triangular or other polyhedral cross section. The shape of the form assembly  5  may be adjusted to accommodate tissue specimens of elongate or eccentric shape and to form specimens into an irregular polyhedron block  3 . 
     In more detail, the form assembly  5  includes wall units  11 , see FIG. 2 where a wall unit  11  is shown inverted, each having a generally L-shaped planar bottom wall  12  coupled with a relatively thin sidewall  13  extending perpendicularly from the edge of the bottom wall and circumscribing an interior reservoir  14 , having an elongate back portion  15  and a shorter, transversely extending leg portion  16 . The bottom wall  12  includes spaced indents  17  for receiving synthetic resin guides  18 , to facilitate movement of the wall units  11  over the base  4  and to prevent scratches which might result in adherence of the tissue specimen  2  to the surface of the base  4 . 
     Each unit sidewall  13  includes an elongate back wall  21 , a generally dog-leg shaped front wall  22  which is slightly shorter in length than the back wall  21 , a first end wall  23  and a second end wall  24 . The upper portion of the front wall  22  flares outwardly to form a lip  25 . Because of the difference in length between the back wall  21  and front wall  22 , the back wall  21  extends beyond the short end wall  23  so as to form a planar flange  26 . A hinge  31  intercouples the flange  26  with a rotatable panel  32  that is adjustable and rotatable about the hinge  31  to join with the flange  26  at an infinite number of angles. The second end wall-facing surface of the panel  32  is coupled with a magnet  33  positioned on one side thereof. 
     A generally L-shaped magnet cage  34  (see FIG. 4) is positioned in each unit reservoir  14  and has a back  35  coupled with a perpendicularly extending leg  36 , the back including a plurality of spaced apertures  37 . The cage leg  36  is coupled with a magnet  38  positioned on one side thereof. The cage  34  is designed for registry with the reservoir  14 , so that, when in place, the magnet  38  is positioned in the reservoir leg portion  16 , and the back  35  rests against the reservoir back wall  21 . The remainder of the reservoir back portion  15  which is not occupied by the cage back  35  may be doped or filed with cotton  39  or other suitable dampering material. 
     Magnets  33  and  38  are employed to selectively magnetically join or couple the wall units  11  in backward facing relationship in an infinite number of positional relationships. The magnets  33  and  38  also hold the units  11  in place so that back walls  21  and panels  32  cooperatively frame a form assembly  5  which is horizontally adjustable along multiple axes. The illustrated magnets  33  and  38  are generally square in shape although it is foreseen that many shapes may be used in accordance with this invention. Magnets  33  and  38  are permanent and may be constructed of any suitable magnetic material. 
     As best shown in FIGS. 1 and 4, in use the wall units  11  are joined in a selected configuration best suited to form the basic tissue sample  2  into the desired block  3 . The intercoupled wall units  11  are supported by a base  4 , having a platform  41 , a base plate  42  and an overflow tray  43 . The platform  41  has a planar deck  44  presenting an upper surface  45  that is supported by dependent sidewalls  46 . The deck  44  includes a plurality of peripherally spaced slots  51 , and the sidewall  46  includes a pattern of spaced apertures  52 . As will be discussed later, cryogenic liquid is used to cool the apparatus  1  and the slots  51  and apertures permit excess cryogenic liquid  53  flowing away from the form assembly  5 , to pass downwardly to collect in the overflow tray  43 . The platform upper surface  45  includes a recess  54  for receiving a temperature sensitive indicator strip  55 , and specimen orientation indicia  56 . The indicia  56  may be stamped, engraved or printed onto the surface  45 . Alternatively, it is foreseen that a movable tag bearing the indicia  56  may be placed on the surface  45  and held in place by a magnet, or other suitable means. 
     The platform  41  surmounts an imperforate planar base plate  42 , presenting upper and lower surfaces  61  and  62  and a perimeter margin  63 . The plate  42  is sized for registry with the platform  41 , so that the deck  44  rests upon the plate upper surface  61  and the plate perimeter margin  63  fits within the circumscribing sidewalls  46  of the platform  41 . 
     Except for the panels  32 , the wall units  11  and base platform  41  are preferably constructed of aluminum or other material having a high coefficient of thermal conductivity. The panels  32 , magnet cage  34  and base plate  42  are constructed of a magnetic stainless steel alloy or other suitable material which is subject to the attractive forces of magnets  33  and  38 . 
     The platform-surmounted plate  42  is supported by a tray  43 , having an upper surface  64 , four side walls  65 , and a lower surface  66 . The upper surface  64  includes a planar central portion  71  bounded by a narrow recess  72 , configured to receive the dependent platform sidewalls  46 . The outer perimeter of the recess  72  is bounded by a substantially wider, shallow trough  73  for receiving any overflowing cryogenic liquid  53 . The tray  43  includes a planar margin surface  74  circumscribing the outer perimeter of the trough  73 . The tray  43  is preferably constructed of a synthetic resin or plastic, such as polyvinyl chloride or other suitable material. 
     A cover unit  6  includes a specimen cover  78  and a cover plate  79 . The specimen cover  78  is preferably constructed of a transparent synthetic resin material or plastic which may be trimmed to fit the surface dimensions of the desired shape of the specimen compartment  7 . The cover plate  79  is generally L-shaped, having a collar portion  80  and a planar portion  81 . The cover plate  79  is constructed of a magnetizable material, such as a magnetizable stainless steel alloy, so that attraction of the collar portion  80  to the form assembly magnets  33  and  38 , holds the cover plate  79  in place surmounting the specimen cover  78 . 
     An excised tissue specimen  2  is generally amorphous in shape, although it may be regular or irregular. The base platform  41 , wall units  11  and cover plate  79  cooperatively form a specimen-receiving compartment  7  that is selected to best fit the specimen  2  and form it into the block  3  having planar walls. While the purpose of the compartment  7  is to form the specimen  2  into a solid polyhedron block having plane faces, the shape of the compartment  7  may be adjusted to conform generally with that of the specimen  2 . If the specimen is elongate or otherwise eccentric, an irregular polyhedron having incongruent plane faces may be formed by manipulation of one or more of the magnetic wall units  11 . 
     The specimen preparation apparatus is used in association with a knife  85 , depicted in FIG.  3 . The knife  85  is preferably a hand-held thermocutter, having a handle  86  and a generally straight blade  87 . The handle  86  incorporates a transformer which heats the blade  87 . The handle  86  may also include a temperature controller as well as a switch. 
     In use, a surgeon excises a tissue specimen  2  to be prepared for tumor margin surface area examination and places it in the approximate center of the base platform upper surface  45  so that the anatomical orientation of the specimen  2  corresponds to the platform orientation indicia  56 . An operator places three or more wall units  11  in upstanding position on the base platform surface  45  with the back wall surfaces  21  facing the specimen  2  and the panels  32  in closed position with the magnet  33  resting adjacent the flange  26 . The operator urges the wall units  11  toward the specimen  2  in order to approximate the overall shape of the specimen  2  and continues convergent movement of the units  11  until the back wall surfaces  21  engage the tissue specimen  2  with sufficient force to conform the generally curvate surfaces of the specimen  2  to the planar wall surfaces  21 . In order to hold the wall units  11  in place against the tissue specimen  2 , the panels  32  are rotated about the hinges  31  so that each magnet  33  is attracted through back wall  21  to either a cage back  35  or another magnet  38 . In addition, the attractive forces of magnets  33  and  38  to the base plate  42  serve to maintain the form assembly  5  in place on the base  4 . 
     The operator trims the cover  78  to the surface dimensions of the specimen compartment  7 , and places it atop the specimen  2 . The operator installs the cover plate  79  over the specimen cover  78 , pushing it downwardly so that the cover  78  engages the tissue specimen  2  with sufficient force to conform the generally curvate surfaces of the specimen  2  to the planar cover surface  78 . The position of the cover plate  79  is maintained by attraction of the collar  80  to one or more of the magnets  33  and  38 . 
     Once the tissue specimen  2  is engaged by the surfaces of the specimen compartment  7 , an operator pours a cryogenic liquid, such as liquid nitrogen  53 , over the lip  25  and into each reservoir unit  14 , pouring additional liquid nitrogen over the specimen compartment cover plate  79 . The liquid nitrogen  53  flows through cage apertures  37  to cool the specimen-contacting back walls  21 . Some liquid nitrogen flows out of the specimen compartment  7  at the joints between wall units  11  and flows through platform slots  51  and apertures  52  to partially fill the tray recess  72 . Any excess cryogenic liquid  53  overflows the recess  72  and is collected in the trough  73 . 
     The operator monitors the temperature indicator strip  55 , and when a predetermined, optimum temperature for tissue cutting is reached, the operator disengages the cover plate  79 , specimen cover  78  and wall units  11  to release the frozen specimen. In order to facilitate release of the specimen block  3 , the operator may remove the liquid nitrogen from the reservoirs  14  by lifting the unit from the tray and pouring off the cryogenic liquid  53 , or by use of an automatic pipette or other similar means. 
     Those skilled in the art will appreciate that the reservoir rear walls  21  may be equipped with heating elements which may be actuated to facilitate release of the specimen block  3 . Alternatively, the operator may apply heat from an external source to the walls  21  using a wand. 
     Once the form assembly  5  and cover unit  6  are removed, the block  3  may be removed from the base assembly  4  for harvesting of the planar tissue surfaces. In preferred embodiments a thermal knife  85  is employed to quickly cut through the frozen tissue. The tissue margin surfaces, such as cut specimen surface  90 , are labeled, mounted on object holders and thin-sectioned on a microtome, such as a cryostat for viewing under a microscope. 
     If malignant cells are observed on one or more of the tissue margin surfaces, the anatomical orientation is noted, and an additional specimen is surgically excised from the corresponding location, and the process is repeated until all possible malignant cells are removed. If additional excision is not possible, the anatomical orientation of the residual malignancy is recorded for use in radiation therapy. 
     II. Apparatus With High Gauss Permanent Magnet 
     As best shown in FIG. 5, a second embodiment of a specimen preparation apparatus  101  for forming a tissue specimen  102  is illustrated. The structure of this embodiment is substantially identical to that previously described, except that high-powered magnets are employed, obviating the need for the larger magnets and magnetically attractive magnet cages previously described. 
     The specimen preparation apparatus  101  includes a base assembly  104  supporting a form assembly  105 , and cover unit  106 . A specimen receiving compartment  107  is cooperatively formed by the magnetic coupling of wall units  111 , each having a bottom wall  112 , coupled with a sidewall  113  circumscribing an interior reservoir  114 , having an elongate back portion  115  and a shorter, leg portion  116 . The wall units  11  in FIG. 5 are joined to form a block  102  with a trapezoidal cross section. 
     The sidewall  113  includes a back wall  121 , extending beyond a front wall  122  in a planar flange  126 , first and second end walls  123  and  124 , and a hinge  131  coupling the flange  126  with a panel  132 . A pair of magnets  133  and  138  is employed to couple the wall units  111  in backward-facing relationship. The magnets  133  and  138  are generally disk-shaped and are constructed of a particularly high Gauss material. Rare earth permanent magnet compounds such as, for example, neodymium-iron-boron are particularly preferred. Because of their strength, magnets  133  and  138  are substantially smaller in size than the panels  132 , and are generally disk-shaped. 
     The intercoupled wall units  111  are supported by a base assembly  104 , having a platform  141 , base plate  142  and base tray  143 . A cover unit  106  includes a specimen cover  178  and a cover plate  179  that is magnetically attractable and having a collar portion  180  and a planar portion  181 . 
     In use, three or more wall units  111  are positioned on the base platform  141 , with the back wall surfaces  121  facing a tissue specimen  102 . Magnets  138  are placed in reservoir legs  116  in contact with the bottom wall  112 , and are magnetically attracted to the base plate  142 . Each panel  132  is rotated about hinge  131  until it contacts an adjacent back wall  121 . The operator positions a magnet  133  at a location on the inside surface of the reservoir back wall  121  so that the magnet  133  is attracted to the panel  132 . The operator installs the cover plate  179  over the specimen cover  178 . The operator may adjust the location of a magnet  133 , if necessary, so that attraction of the magnets  133  to the collar  180  holds the cover plate  179  in place. 
     Those skilled in the art will appreciate that tissue specimen  102  may be conformed to the back wall surfaces  121  until it completely fills the specimen compartment  107  to the upper margins of the walls  121 . In that case, the cover plate planar surface  181  may held in place atop the wall units  111  by one or more additional magnets (not shown) placed atop the planar portion  181  in magnetic attraction with one or more magnets  133  or top margins of panels  132 . 
     III. Cube-Forming Apparatus 
     FIGS. 6-10 depict a third alternate embodiment of a specimen preparation apparatus  201 , suitable for use to form a generally regular tissue specimen  202  into a polyhedron block having a 90° angle at each of the vertices, such as a cube or other solid with a generally rectangular cross section. 
     In more detail, the specimen preparation apparatus  201  includes a base assembly  204  supporting a form assembly  205  and cover unit  206 . A specimen receiving compartment  207  is cooperatively formed by four magnetically coupled wall units  211 , each having a generally rectangular bottom wall  212  orthogonally coupled with a sidewall  213  circumscribing an interior reservoir  214 , having a back portion  215  and a front portion  216 . 
     The sidewall  213  includes generally rectangular back and front walls  221  and  222 , and a pair of generally square end walls  223  and  224 . The endwalls  223  and  224  are coupled with one or more generally square-shaped magnets  233  and  238 . Either or both of the magnets  233  and  238  may have multiple individual magnetic units. A generally rectangular spacer unit  240  of a synthetic resin material occupies the reservoir front portion  216 , and the remaining reservoir back portion  215  is filled with cotton  239  or other suitable dampering substance adapted to receive cryogenic fluid. The magnets  233  and  238  are employed to couple the wall units  211  in generally end to side relationship and to maintain the wall units  211  in place to frame a form assembly  205 , which is adjustable along the X and Y axes. 
     The intercoupled wall units  211  are supported by a base assembly  204  having a base plate  242  and base tray  243 . A cover unit  206  includes a specimen cover  278  and a magnetizable cover plate  279 , having a collar portion  280  and a planar portion  281 . 
     In use, the form assembly  205  operates much as previously described. A surgeon excises a tissue specimen  202 , having an irregular curvate surface. The specimen is placed on the base platform  241 , and four wall units  211  are positioned on the platform  241 , with the back wall surfaces  221  facing the specimen  202 . An operator moves the wall units  211  along the X and Y axes to converge toward and exert force on the specimen  202  until the reservoir back wall surfaces  221  engage the curvate surfaces of the tissue specimen  202  and reform the tissue into a block with generally planar surfaces. The wall units  211  are held in place by the attraction of magnets  233  to magnets  238 , and by the attraction of all of the magnets to the base plate  242 . The operator trims the specimen cover  278  to fit and installs it in contact with the upper surface of the specimen  202 . The cover plate  279  is then installed over the specimen cover, forming the specimen into a six-sided block. The cover unit  206  is held in place by attraction of magnets  238  to the collar portion  280 . The operator pours a cryogenic liquid  253  into reservoir back portions  215  to chill the specimen  202 . 
     It is understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangements of parts described and shows.