A geneticist is a medical professional that works in the field of genetics. A geneticist can specialize in agriculture, biomedicine, forensics, archaeology and bioinformatics among others. A geneticist will perform tasks such as planning and conducting research. They also keep notes that record their methodology, procedures and results while results are analyzed via mathematical and statistical methods.
What is a Frozen Section?
A frozen section is a term referring to a section of tissue that has been rapidly cooled using cryostat. It is an important feature that is needed in hospitals to assist with the diagnoses of lesions and the extent of the lesion during surgery. The cryostat is an instrument used to freeze the human tissue samples and cut it for microscopic section. It is used to aid in the immediate diagnosis of lesions to help medical professionals plan the management for the relevant patient. Frozen sections are also helpful for immunofluorescence and enzyme immunochemistry studies. Another useful indication would be to stain certain carbohydrates and lipids present in the tissue.
The Principle of Frozen Section
When the tissue sample goes through rapid freezing, it converts water into ice which acts as an embedding media allowing the tissue to be sectioned. The tissue can become firmer if the temperature of the tissue sample is lowered while increasing the temperature softens the tissue. Some important factors to note are:
The temperature range in the cryostat machine usually ranges from 0⁰C to -35⁰C. The majority of the tissue can be appropriately sectioned between -15⁰C to -25⁰C. Tissue samples that contain water can be sectioned at a higher temperature while tissues that contain more fat will need to be cut at a lower temperature.
The knife inside the rotary microtome is fixed, and the tissue can be moved with the help of the rotary wheel.
A tissue shelf in one side of the microtome can be used to keep the tissue. This helps to keep the samples at a freezing temperature as the temperature in the tissue shelf is usually lower compared to the cabinet temperature.
There is a small place to place the knife and brush holder in front of the microtome machine.
To obtain an even pressure during sectioning of the tissue samples throughout the whole length, the blade should be fixed to the holder with the knife angle kept between 5⁰ to 7⁰.
An antiroll plate is available in front of the knife to prevent the rolling of the tissue during the cutting process. The antiroll plate is usually glass within a metal frame.
A cool sable hair brush is also available to obtain unrolled tissue.
Depending on the manufacturer, the specimen holder can be available in various shapes and sizes.
The optimal cutting temperature (OCT) compound such as resin and water-soluble glycols will be used as an embedding medium to hold the tissue.
The tissue sample and requisition form should first be identified.
Look at the clinical information available as it can help achieve the possible differential diagnoses.
Observe the gross appearance of the tissue in terms of color, consistency, texture, and presence of sutures used to mark the anatomical position of the sample.
Identify the resection margins and planes. Use different ink colors for identification of medial and lateral margins.
When cutting the tissue, ensure that the tissue is fresh, preferably dry, and free from any gauze, sutures, or staples. The tissue is then cut into multiple small pieces to assist freezing. Multiple sections of the tissue should be obtained to help minimize error and understand the primary pathology. Use a sharp blade to cut the most crucial area using gentle pressure.
To embed tissue in the mold, keep a small piece in the center of the mold and pour OCT in excess over it. A tissue holder is then placed over the tissue.
Place the tissue in the frozen section chamber. To hasten the process, cold spray can be used.
Load the cutting knife at the proper alignment.
Once the tissue is frozen, it will appear whitish. Place the in frozen tissue the holder of the microtome and trim to remove the excess OCT. This prepares the tissue surface for sectioning.
Cut the tissue gently and spread it over the antiroll plate using a cooled brush.
Press a glass slide firmly over the section and fix immediately in methanol for 1 minute. 95 percent ethanol can also be used for tissue fixation (for a few seconds). Rapid fixation is a must as a delay results in swollen cells and hazy cell margins.
Staining is usually done using hematoxylin and eosin (H&E) and toluidine blue stain. The slide is first rinsed in tap water and put in hematoxylin for a minute. It is then rinsed in tap water for 5 seconds followed by another rinse in Scott's tap water for another 5 seconds. The slide is then dipped in eosin for 20 seconds and rapidly rinsed in tap water after.
The frozen section refers to the process where there is rapid tissue section cooled with a cryostat to provide an immediate report of the tissue sample. The cryostat freezes the tissue allowing it to be cut for a microscopic section. The conversion of water into ice acts as the embedding media for cutting the tissue. It is a technique that is mostly used for the rapid diagnosis of lesions during intraoperative management. This helps to determine the extent of the lesion, allows for immunofluorescence and immunohistochemistry study, and staining of specific carbohydrate and lipid in the tissue. This article has described the principle, techniques, indications, and instructions on how to make a good quality frozen tissue section.
Dey P. (2018) Frozen Section: Principle and Procedure. In: Basic and Advanced Laboratory Techniques in Histopathology and Cytology. Springer, Singapore.
A biopsy is a test that is used to help determine the composition and structure of the cells and tissues of the body. The test can be used to evaluate human tissue samples from part of the body to allow the examination of the tissue sample under a microscope. Since most biopsies are minor procedures, patients do not usually require sedation. Patients may only require local or no anesthesia. The term biopsy is of Greek origin “bios” and “opsis” where the word “biopsy” can be loosely translated to “appearance of life” or “view of the living”. Biopsy is a good way to evaluate for the presence of malignancy or for confirmation if the abnormality is benign. If there is cancer, a pathologist studies the tissue sample to determine the type and grade of malignancy.
Why is a Biopsy Performed?
A biopsy is usually performed when there are lesions that can be felt or seen on imaging such as ultrasound, X-ray, computed tomography (CT) scan, or magnetic resonance imaging (MRI) scan. The biopsy is used to help determine the nature of the suspected abnormality. In cases of suspected cancer, the biopsy helps determine if the area involved is malignant or benign. One good example is the biopsy of a breast lump for histologic examination to determine if it is cancerous. The laboratory analysis of the specimen is performed by a clinical pathologist. A definitive and correct diagnosis is usually arrived through histological and cytological examination.
When a tumor is malignant, biopsies of the lymph nodes and surrounding tissues are performed to determine if the cancer has metastasized. Biopsy also helps to determine the grade of cancer. Surgical biopsy is a procedure that removes the entire tumor and can be done with the guidance of endoscopy or imaging. The pathologist can usually tell if the cancer is a slow or aggressive form.
Types of Biopsies
There are many types of biopsies. The type of biopsy used for the patient will be determined based on several factors such as:
• Location, body part, or organ to be sampled
• Number of lesions
• How suspicious the lesion appears to be
• Characteristics such as shape and size of the lesion
• Existing comorbid and patient preference
• Facilities and systems available at the current healthcare facility
Some examples of biopsy procedures include
a) Aspiration or fine needle aspiration (FNA) biopsy
b) Cone biopsy
c) Core needle biopsy
d) Endoscopic Biopsy
e) Surface biopsy
f) Vacuum assisted biopsy
g) Punch biopsy
h) Surgical biopsy or excisional biopsy
Image Guided Biopsy
There are many biopsy procedures that are done with the help of image guidance such as CT and ultrasound. There are many breast biopsies that have been done with the guidance of stereotactic mammography. CT is increasingly used to guide the biopsy of liver and lung lesions. Interventional CT now helps to allow real time CT imaging during biopsy increasing diagnostic accuracy and shortening procedure times. Ultrasound is also useful as it offers great flexibility to follow the path of the needle to the lesion, provide real time display, and allows professionals unlimited imaging. In stereotactic mammography, it helps to show images of two angled directions to guide the needle. MRI helps provide real time images that guides the trajectory of the needle approaching the lesion. It also provides a high contrast resolution helping radiologists to differentiate between abnormalities and organ structures.
Risks of Biopsy
Although biopsy is a minimally invasive and relatively safe procedure, there are still certain risks that are involved. Some examples of risks for needle biopsy include:
• Infection of the area being biopsied
• Puncture of structures near the biopsy target
• Vasovagal response
For surgical biopsy, risks include
• Scarring due to stitches after excision
• Mortality due to risks of anesthesia
• Possibility of infection, bleeding, and delayed wound healing
• Longer recuperation necessary compared to needle biopsy
Biopsy results can be negative or positive. A negative result usually means that there are no abnormal cells seen in the examined tissue sample while a positive result means that abnormal cells are seen in the cell sample. Abnormal results help to identify:
- A possible infectious agent, changes to the cells caused by infection or disease.
- The presence of a benign growth or process.
- The presence of abnormal cells where cancer cells are seen. With these findings, the pathologist may be able to determine the origin of cancer cells to see if it is from a primary tumor or from metastasis.
Who Performs Biopsies?
Biopsies can be performed as an outpatient or inpatient bases by medical doctors or doctors of osteopathy. Surgeons are individuals who perform excisional and open biopsy. More invasive percutaneous biopsy such as the liver or lungs will be performed under guidance of medical imaging usually by a radiologist .The biopsy specimen is then analyzed by a pathologist who then renders a medical diagnosis based on the tissue sample.
1) Biopsy procedure – what is a biopsy. Imaginis. Accessed 12/11/2018. http://www.imaginis.com/biopsy/biopsy
2) What is biopsy: overview, benefits, and expected results. Docdoc. Accessed 12/11/2018. https://www.docdoc.com.sg/info/procedure/biopsy/
What is a Biorepository
A biorepository is a center that functions to:
Biospecimens help support present and future research studies and investigations. It is a place where various specimens from many living organisms such as, animals and humans are contained and managed. Many life forms such as arthropods, vertebrates and invertebrates can be analyzed and studied through the preservation and storage of their tissue samples. Besides maintaining the relevant biological specimens, biorepositories also have a role to collect the associated information from these specimens for future use in research. One of the most crucial roles the biorepository plays is to ensure the quality of the collected samples. They also have to manage the accessibility of biospecimens while handling the disposition and distribution of their collection.
As previously mentioned, the four main operations of a biorepository are collection, processing, storage and distribution. For elaboration purposes:
a) Collection – This is the first step where biospecimens are obtained and recorded in the records. This can be done by scanning the sample’s barcode where the information regarding the sample is then transferred into the biorepository’s laboratory information management system. Examples of the information recorded would include the origin of the sample and the time the sample arrived.
b) Processing – This phase involves the testing of the biospecimens to minimize variation and preparing them for storage. One example is the processing of DNA samples into a salt buffer to stabilize the DNA for long-term storage.
c) Storage – After the biospecimens are collected and processed, they are stored accordingly based on the required temperature and environment. Some samples are stored in freezers while some can be stored at room temperature. This is where all biospecimens are held before distribution.
d) Distribution – This occurs when the biorepository fills an order or request from a research team from the biorepository’s inventory system.
Biorepository Standard Operating Procedures
Standard operating procedures or SOPs are vital in a biorepository. It helps to:
· Minimize variation between samples and reducing issues through standardized guidelines
· Ensure that biospecimens closely resemble their natural state
· Provide a framework of how operations should be conducted in a biorepository
· Ensure reliable and seamless process during operations
· Provide guidelines for backup during emergencies
An Overview of Biobanks
A biobank is a type of biorepository that stores biological samples that are usually human for research. Biobanks are an important resource for medical research as it helps support various types of contemporary research. It allows access to data for researchers that represent a large population. Samples and data available in biobanks can also be used by many different researchers for various studies. This is crucial as there are many researchers who have difficulty acquiring samples before biobanks existed.
Although many issues such as privacy, medical ethics, and research ethics have been raised, a consensus has been reached that operating biobanks should consider the policies and governing principles that protect the communities that participate in their programs. The term “biobank” can be defined as “an organized collection of human biological material and associated information stored for one or more research purposes”. While biospecimen collections from other living organisms can also be called biobanks, many prefer to reserve the term only for human biospecimens.
Types of Biobanks
Biobanks can be classified based on their purpose or design. Both the terms “biobanks” and “biorepositories” have been used interchangeably. In the United States, the National Cancer Institute thinks of biorepository as a place or organization where biospecimens are stored. The term “biobank” is also being used in the same context in the United States and European institutions. Biobanks can be classified based on different approaches such as:
Hospital or academic based biobanks
Non-profit organizations or commercial companies
Biobanks can also vary in nature, contents, participants, and scale. For example, a human biobank can be classified based on the tissue type, their research purpose, or ownership of the biobank. The size of the biobank can be based on the disease group, national, statewide, or regional. Other experts classify biobanks into four different basic types:
Clinical or control based biospecimens from non-diseased donors and donors with specific diseases.
Biobanks that follow their participants over a long period of time, also known as longitudinal population-based biobanks.
Biobanks with twin registries that obtain samples from both dizygotic and monozygotic twins.
Population isolate biobanks that have a setup using homogenous genetic donors.
Despite the various classifications of biobanks from various experts, the currently accepted classification is from the pan-European Biobanking and Biomolecular Resources Research Infrastructure (BBMRI). They distinguish only two types of biobanks which are:
Disease-oriented biobanks where it contains clinical data and tissue samples
Population-based biobanks where the focus is on the study and development of complex and common diseases.
In conclusion, both the terms “biorepository” and “biobank” are often used interchangeably as the distinction is blurry. However, one of the most significant differences is that biobanks often refer to collections of human biological material while biorepositories can refer to collections of all living organisms.
1) Biorepository. Wikipedia. Accessed 11/8/2018. https://en.wikipedia.org/wiki/Biorepository
2) Biobank. Wikipedia. Accessed 11/8/2018. https://en.wikipedia.org/wiki/Biobank
3) Kinkorova J. Biobanks in the era of personalized medicine: objectives, challenges, and innovation. EPMA J. 2016; 7(1):4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4762166/
FFPE Tissue Blocks is a great commodity to the research and medical field as it is an inexpensive and easy way to store and archive Human and animal tissue specimens. It also preserves the integrity of the specimen for a long time and can therefore be used retrospectively in many studies which reduces the time needed to track down specific tissues that fit the criteria of the study.