Extraction of tissue and body fluids

Author:  Gesche Tallen, MD, PhD, Editor:  Maria Yiallouros, Reviewer:  Prof. Dr. med. Dr. h. c. Günter Henze, English Translation:  Hannah McRae, Last modification:  2015/04/22

The extraction of tissue and body fluids requires penetration into a patient's body. Therefore, the corresponding techniques like biopsy and puncture (please see below), are called invasive procedures. Biopsies and punctures are performed to obtain material for special laboratory tests, such as blood, cerebrovascular fluid or bone marrow tests.

Laboratory tests based on the analysis of biopsied tissue or punctured fluids are needed to further define the diagnosis of a childhood cancer, as well as to monitor its response to therapy as well as to detect possible treatment- and/or disease-related side-effects.

Biopsy

In paediatric oncology, the term “biopsy” refers to the extraction of a tissue sample indicative of cancer. Biopsy samples are necessary for getting detailed information on the disease, such as the origin and type of the cancer cells and their growth behaviour. This information is required to plan the treatment.

A biopsy can be done by a puncture with a fine needle or by the use of certain surgical instruments. Biopsies can also be performed as a surgical procedure (for example as a sample-excision during open surgery, as a so-called stereotactic biopsy, during a laparoscopy). Most biopsies are considered to be minor surgical procedures.

For a biopsy, young patients are usually sedated or receive anaesthesia (depending of the extent of the biopsy). A biopsy in a child or teenager under 18 years of age can only be performed after informed consent of the parents or legal guardian.

Puncture

The term “puncture” generally refers to the insertion of a hollow needle into a blood vessel, body cavity, tumour tissue and/or normal tissue. Diagnostic punctures are done to obtain liquid or tissue for the purpose of laboratory testing and/or histological (microscopical) examination. The use of ultrasound (please see ultrasound) and computed tomography imaging procedures (please see computed tomography) is frequently used to visualise the exact location of the area to be punctured.

Laboratory tests based on tissue or body fluids obtained by biopsy or puncture

Tissue and blood samples obtained by biopsy or puncture, respectively, are tested in routine or special laboratories depending on the type of tissue and the information needed to plan the treatment.

In a so-called histopathology laboratory, the extracted material is first processed by a pathologist to be examined under a microscope. The pathologist carrying out the investigation (for example, a paediatric pathologist or neuropathologist) has a major role in the caregiver team of a child with cancer, since he or she decides whether the tissue under the microscope is cancerous or not.

The pathologist must also conclude what type of cancer is present, as well as recognise any special characteristics the cancer tissue may have on a microscopic or molecularc level. The word of the pathologist is therefore the ultimate diagnosis, pursuant to the results of any other examinations.

To avoid the risk of error, each sample of each child is also reviewed by a pathologist in a second and a third paediatric oncology treatment centre. Bone marrow and blood samples from patients leukaemia or lymphomas are additionally investigated by a paediatric oncologist.

The following biopsy and puncture techniques are described in this chapter: