Fragile bones are challenging specimens while grossing in surgical pathology. Among them the most vulnerable are bones in the maxillary ethmoidal area, but even a rib can be damaged by an inappropriate cutting technique. Needless to say that some bone/soft tissue tumors, malformations or bones with degenerative disease present various technical particularities during grossing and decalcification.
These remarks are the continuation of the previous detailed description of the general approach to bones processing presented in “Bones in the surgical pathology grossing room” and “Grossing technique of a mandible bone” articles (link “Grossing Techniques”). Some references will be made to devices that enhance the technical abilities while grossing (link “Instruments and Gadgets”). The main goal is to provide specific details that are crucial in successful fragile bones processing.
Three main principles of bone processing should be reiterated: Immobilization, Appropriate cutting instrument, and Definite area of cutting. They apply to fragile bones as a necessity. In most cases there is no a second chance to repair a wrong cut.
The maxillary bone is a difficult specimen due to the combination of firm facial scull bones and fragile bones of the maxillary sinus. Usually there is only a part of the maxilla with attached tumor. In most cases the diagnosis is known already. The main goal of the examination is predominately to determine the relationship between the tumor and the surrounding tissue, especially bones.
If it is necessary to make serial sections and there are enough firm bones, the immobilization in a vise is the best option (See “The vise on the grossing table” at the link “Instruments and gadgets”). The specimen is wrapped in paper or small bubble wrapping material and placed in the vise throat’s center as much as possible, in order to have the sinus part exposed to the cut.
Fig. 1 Maxillary sinus in the vise’ throught.
However, occasionally an eccentric placement of the specimen does not provide a satisfactory immobilization. The vise, although appropriate for serial sections, cannot be used for the final cut of the bone that is held by the vise’s jaws. The final cut requires a firm surface outside the vise, but as the main cuts have already been completed, this is relatively easy task.
Serial sections are rare and, unfortunately, often the maxillary specimens do not have enough firm bones to be held by the vise’s jaws. It seems that the most universal immobilization device for maxillary bone specimens is hard- pressed carton. (See “Hard-pressed packing carton in grossing room” at the link “Instruments and gadgets”). There are a variety of configurations of the packing carton that can be adjusted to the various configuration of maxillary bones surgical specimens. The most available as well as the most suitable is the cup holder of a disposable cafeteria tray. Slightly wet paper (the best is White All Purpose towel) is put beneath and around the specimen, making it congruent to the shape of the carton “mold”. If the procedure is not performed in a hurry (rare situation), the sinus can be stuffed with paper for better immobilization of the specimen’s most vulnerable part.
For most fragile bones, the cutting instrument of choice is a hand saw, although in rare occasions, a mechanical saw, for example Stryker type, can be used. The general rule for the choice of a saw is: the thinner the bone, the lighter the saw, with the blade ranging from 24 to 32 TIN. I prefer Mini Hack Saw. Another important requirement is that the blade should be in the metal variant that makes the cut more manageable, although it takes more time. Sometimes it is a good idea to use Liston Bone Cutting Forceps for initial cut of the thinnest part of the walls of the maxillary sinus, followed by the saw.
Unless it is necessary for some diagnostic reasons, the cut should be initiated and followed eccentrically to ensure effective immobilization by the holding device (a vise, a forceps, a clamp or …a hand). Sometimes the section comes out thicker than it is intended. Although there are methods to make it thinner immediately, it does not make any sense to do so because it is easier and more effective to trim after fixation and decalcification.
Speaking of decalcification, it is imperative to mention that although there is an opinion that maxillary specimens arrive with a known diagnosis and they can be placed for decalcification entirely after the fixation process, appropriate cutting technique can help to avoid this violation of the rules of tissue processing. (See “Bones in grossing room” at the link “Grossing techniques”).
A rib is an example of different kind of fragile bone, as an incidental specimen during a nephrectomy or as part of mediastinal tumor resection. Although the first situation is of no diagnostic importance, a good section requires some technique that includes firm support (better wood or thick hard pressed carton), reliable immobilization (better with a MOPEC’s 10” Russian Tissue Forceps) and a Mini Hack Saw with 32 TIN blade.
The variety of clinical and anatomical situation of a tumor with a rib involvement requires individual approach in each case where the main technical aspect is an appropriate choice of adequate firm support of the specimen. In this regard the best is hard- pressed carton which can be adjusted to the variety of the specimen’s configurations.
Here is a mediastinal tumor that growth in the sternum and ribs placed in a four cup cafeteria tray. This immobilization is optimal for serial sections.
Figure 2. Sternum and the rib section
It is challenging to make longitudinal cuts in ribs from cases of metastases or myeloma. For this procedure, the rib or area of interest of the rib should be cut in straight fragments. The rib is placed on a support device with a border at one side, for example a hard- pressed packing carton box. It is immobilized between the border and piece of wood or Styrofoam. A cut with a 32 TIN blade hacksaw can provide a longitudinal section.
A larynx has a hyoid bone that is not fragile and often contains calcified cartilages. This combination, however, makes the specimen inconvenient for grossing, which leads to completely erroneous recommendation by some pathologist to put the entire larynx in decal after fixation. Appropriate technique can avoid this violation of standard rules of histology and provide satisfactory sections.
These remarks apply only to technique as far as the bone part of cutting is concerned, although there are many details of processing the larynx specimen that are described in dissection manuals. It is assumed that the larynx is flattened, inked, and fixed overnight
The importance of the right choice of the initial cut in a larynx specimen is particularly crucial from a technical point of view. The main rule of grossing dissection, which is the preservation of the specimen’s integrity as a whole, is especially important in this case. The first longitudinal cut should be done on loose immobilized specimen. A hard- pressed carton is the best option, especially a cup holder of a disposable cafeteria tray.
Figure 3. Larynx in a vacuum vise
Some moistened paper is placed beneath and around the specimen to make it congruent to the carton’s mold. If the epiglottis is present, it is best to cut it first. The initial cut through the soft tissues is made to the hyoid bone and cartilage. If the latter is not calcified, the cut can be made with a firm movement of the blade. If there is a resistance, it is best to start sawing of the hyoid bone. The area of the hyoid bone should be placed on the firmest part of the support device. A Mini Hack Saw is preferable. The sawing is continued through the calcified cartilages.
To get a satisfactory sections for histology, the most representative part of the previously cut part of the larynx should be placed in a carton mold in a way that the already cut area is secured against the wall of the mold.
Figure 4. Larynx at the hard pressed carton.
The hyoid bone rarely is of diagnostic importance, but occasionally the pathologist has to answer some questions about hyoid bone involvement. Again, a longitudinal section should start with the hyoid bone. The problem is that sometimes the bone disappears under the saw due to the contraction of the surrounding soft tissue and muscles. Firm pressure by saw can crash the bone while sawing. An option is to press the bone to something steady on the section side (the third hand). After the hyoid bone had been cut, the following section is made with a blade to the point when it has resistance by the calcified cartilage. The Mini Hack Saw is the preferable instrument. The cartilage is pressed against something firm otherwise the section comes out too thick and requires additional trimming under inconvenient condition. When the complete longitudinal section is ready, it is tailored to fit the cassette in the way with minimal soft tissue adhered to the bone or calcified cartilage.
Miscellaneous fragile bones require individual approach. All principles apply to them in more strict form. Some examples do not excide the variety of clinical situations.
For example, a femoral head with avascular necrosis and detached cartilage should be placed with the relatively firm part down on the steady support device (wood or hard- pressed carton). The initial cut should be made with a 32 TIN blade hack saw with a holding forceps close as much as possible to the area of the cut. It is better to finish the sawing with the same blade unless the rest of the bone is too firm or large.
Another example of a challenging fragile bone is a semilunar bone with osteochondrosis (Kienbock disease) that requires a firm grasp with a teethed large forceps (like MOPEC’s 10” or 6” Russian Tissue Forceps) and sawing between the branches with a 32 TIN blade on a steady support surface. (See also “Bones that do not fit the cassette” at the link “Grossing techniques”). The gentle cut maintains all layers of the fragile bone on the section.
A soft tissue tumor adhered to a hard palate can be another example of a fragile bone processing. The diagnosis of bone involvement is very important in this situation. The cut with a knife should start serially from the soft tissue part towards the bone. Then the soft tissue should be cut off. The rest of the specimen is placed on hard-pressed carton between branches of a forceps (better MOPEC’s Russian Tissue Forceps 6”). Sawing with a light pressure of Mini Hack Saw (prevent bone crash!) should continue until the saw’s blade is definitely in the carton.
For bone tumors, malformations, as well as other different kinds of fragile bones the overall handling is similar to above described osteochondrosis bone. The only difference is in the choice of the immobilization device.
In a case of a pathological fracture, sometimes a longitudinal cut is appropriate. This situation requires two kinds of saws: a regular 18 TIN and a Mini Hack Saw to maintain the integrity of the specimen. The fractured area itself should be placed on hard- pressed carton “mold” otherwise the fragile fractured bones fall apart during cutting.
A femoral head with tumor is placed in a hard pressed carton mold that enables to adjust adherent to the bone soft tissue by making serial sections.
Figure 5. Femoral head with a tumor on the hard pressed carton is cut through the carton
Another example of the crucial importance of immobilization is a specimen of a completely removed nose due to squamous cell carcinoma with ulcer at the nose’s dorsum. The specimen is placed in the carton mold and pressed against the mold’s wall.
Figure 6. Resected nose is pressed agaist the vertical wall of hard pressed carton.
After the line of resection margins had been cut that included bone, septal cartilage, turbinates and soft tissue, the specimen was placed in another carton mold to make serial sections of areas of interest.
Figure 7. Resected nose is placd flat on the hard-pressed carton after the margin of resection was cut.
Calcified lymph nodes, for example at hilus of the lung area, can imitate a bone. They require special treatment by using a combination of soft/hard background (hard pressed carton), soft/firm grasp by a holding forceps (Russian Tissue Forceps) and fine saw blade Mini Hack Saw). This technique provides serial sections of the entire specimen with keeping the capsule intact.
Decalcification is a significant particularity in fragile bones processing. All rules of careful timing of decalcification apply to fragile bones, but more diligently. For example, prolonged decalcification in Pindborg tumor can be a reason for difficulties of revealing amyloid by Kongo Red staining. The rinsing after the decalcification also should be made more meticulously.
Decalcification issues require a separate discussion. All efforts during grossing can be compromise as the result of inappropriate decalcification.
Although it requires some training, with the appropriate tools and techniques, satisfactory sectioning of every fragile bone can be achieved.