Glossary

macrocephalus
large head, which can be caused by a hydrocephalus (hydrocephalus) in a child with unclosed fontanelles, but also by a large tumour or both

magnetic resonance imaging
diagnostic imaging method; very precise, radiation-free examination method for the visualization of structures inside the body; with the help of magnetic fields, cross-sectional images of the body are generated, which usually allow a very good assessment of the organs and many organ changes.

measles
an infectious disease caused by the measles virus; it occurs mainly in childhood and is mainly characterised by fever and a rash typical of the disease; leaves lifelong immunity.
Example / Relevance Pediatrics: in immunosuppressed children and adolescents (e.g. in the context of cancer treatment), a measles infection can be life-threatening.

mediastinum
middle section of the thoracic cavity located between the two lungs

medulloblastoma
malignant embryonic (primitive) tumour of the cerebellum; it occurs mainly in infancy and childhood and, at almost 20 %, is the most common malignant solid tumour in childhood and adolescence.

MEN syndrome syn. multiple endocrine neoplasms
MEN stands for "multiple endocrine neoplasms"; a rare hereditary disorder belonging to cancer predisposition syndromes that promotes the cancerous proliferation of hormone glands, affecting at least two different hormone-producing (endocrine) glands; there are three types of MEN syndrome: MEN 1, MEN 2a and MEN2b. MEN type 1 (also called Wermer syndrome) is characterized by adenomas of the pituitary gland, parathyroid gland, and tumours of the pancreas. In MEN type 2a (Sipple syndrome) and MEN type 2b (Wagemann-Froboese syndrome), tumours often form in the thyroid gland, parathyroid glands and adrenal medulla (phaeochromocytoma). Depending on the type, there are different genetic defects that are inherited in an autosomal dominant manner.

meninges
layers of connective tissue that protectively envelop the brain; the three meninges are joined to the outside by the skull bones. In the area of the spinal cord, the meninges merge into the three-layered spinal cord membrane, which surrounds the rest of the central nervous system.

mesenchymal
consisting of embryonic connective tissue; mesenchymal cells have a high ability to divide and can develop (differentiate) into different tissue types, e.g. bones, cartilage, muscles, adipose tissue, tendons, blood and lymphatic vessels.
Example / Relevance Pediatrics: malignant tumours of tissues of mesenchymal origin are called sarcomas.

mesenchymal stem cells
stem cells of connective tissue; they are found in various types of tissues (such as bone marrow, bones, skeletal muscles, cartilage, blood, adipose tissue, connective tissue of the skin) and can develop into different types of cells (including bone, cartilage, muscle, fat cells).
Example / Relevance Pediatrics: malignant tumours of tissues of mesenchymal origin are called sarcomas.

metaphysis
the area in a long bone that is located (close to the joint) between the middle part (bone shaft, diaphysis) and the end piece (epiphysis) of the bone; during the growth phase, the longitudinal growth of the bone takes place in the so-called epiphyseal plate.
Example / Relevance Pediatrics: osteosarcomas usually develop in the area of the metaphyses of the long bones.

metastasis
1. tumour spread from the primary site of tumour to other parts of the body; characteristic feature of malignant tumours (cancer). 2. collective term for a disease process characterized by malignant cells spreading from their primary site to other areas of the body via the bloodstream and/or the lymphatic system.

MIBG syn. Methyliodine benzlyguanidine, 123iodine-meta-iodinebenzylguanidine (123I-mIBG)
a weakly radiolabeled substance that resembles a neurotransmitter of the sympathetic nervous system, the stress hormone norepinephrine (a catecholamine), in its chemical structure.
Example / Relevance Pediatrics: 123mIBG is used in the context of special nuclear medicine procedures (scintigraphy), especially in the diagnosis and therapy of neuroblastomas.

MIBG scintigraphy syn. 123I-MIBG scintigraphy
imaging nuclear medicine technique applied specifically for the diagnosis of sympathetic nervous system tumours by using radiolabeled methyliodine benzylguanidine (123I-MIBG). In children and adolescents, these include, for example, neuroblastoma and phaeochromocytoma as well as their metastases. MIBG is a substance that has similar chemical structure to the bodys own catecholamines (specifically the hormone norepinephrine, a messenger substance of the sympathetic nervous system). It typically accumulates in tumours that can produce catecholamines. Since weakly radioactive iodine is coupled to the MIBG, the tumour cells enriched with this substance emit signals that can be recorded by a special camera and processed into an image.

MIBG therapy
treatment with radiolabeled methyliodine benzylguanidine (MIBG; 123-I-MIBG), a substance that accumulates primarily in catecholamine-producing tumours of the sympathetic nervous system (e.g. neuroblastoma). The radioactive dose is chosen so high for treatment purposes that the tumour tissue is irradiated "from the inside" by the MIBG accumulation and is subsequently destroyed.

microorganisms
microscopic organisms that are usually not visible to the naked eye; microorganisms include single-cell organisms, bacteria, some fungi and viruses. Some microorganisms can cause infectious diseases.

microscope
an instrument that allows you to magnify objects or certain structures of objects that are not visible to the human eye

midbrain
part of the brainstem; adjacent to the diencephalon at the top and the bridge at the bottom, the latter of which is also part of the brainstem. In the midbrain, there are important pathways that ascend and descend between the brain and the spinal cord. The midbrain is also home to the eye muscle nerves (cranial nerves III and IV) and to the nerve cell nuclei for certain muscle activities (e.g. of the face and neck).

molecular
at the level of molecules

molecular biological
referring to the structure, formation, function and interactions of DNA and RNA (with each other and with proteins) at the molecular level
Example / Relevance Pediatrics: molecular biological methods play an important part in modern biological and medical research.

molecular genetic
referring to structure, formation, development, function and interactions of cells and cell building blocks (e.g. nucleic acids, proteins) at the molecular level; the focus is on the analysis of the genetic information stored in the nucleic acids (DNA and RNA) and its processing in the context of protein synthesis as well as gene regulation.

molecular genetics
a branch of genetics and biology that investigates the inheritance, structure, metabolism, differentiation and interactions of cells at the molecular level; the focus is on the analysis of the genetic information of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) and their processing in the context of protein synthesis as well as gene regulation.

molecule
chemical compound of two or more atoms joined together

monoclonal antibodies
antibodies produced by the derivatives of a single B lymphocyte (cell clone) that are completely identical; they can be genetically engineered for diagnostic and therapeutic purposes and target a small molecular segment (epitope) of a specific antigen.

monocytes
subtype of white blood cells (leukocytes); after maturing in the bone marrow, they circulate in the blood for one to two days and serve as an immune defense. Subsequently, they migrate into various tissues and develop there into local, tissue-typical macrophages ("large scavenger cells").

monosomy 7
congenital condition associated with an increased risk of developing acute myeloid leukaemia (AML); the disease is caused by a genetic change (mutation) in which chromosome 7 is only present in a single rather than double version due to chromosome loss.

morphological
in this context: concerning the structure and shape of tissues or cells; the term morphology comes from the Greek and means "study of shape/form". As a branch of biology, morphology is the study of the structure and shape of organisms, their tissues and cells. At the cellular level, this is referred to as "cytomorphology".

MRI
abbreviation for magnetic resonance imaging, a very precise, radiation-free examination method for imaging structures inside the body

mTOR inhibitor syn. mechanistic target of rapamycin inhibitor (mTOR)
an active component (agent) that inhibits the mTOR signaling pathway, which plays a crucial role in the cell cycle; mTOR is a kinase found in all mammals, i.e. an endogenous enzyme. It regulates various processes at the central level and controls cell metabolism as well as growth, maturation and reproduction of cells.

mucoepidermoid carcinoma
rare malignant tumour of the salivary glands

mutation
alteration of genetic material; it can arise without any identifiable external cause (so-called spontaneous mutation) or be caused by external influences (induced mutation). External influences include, for example, ionizing radiation or certain chemical substances (mutagens). If somatic cells are affected, it is referred to as a somatic mutation, and if germ cells are affected, it is referred to as a generative mutation. Somatic mutations are not heritable, while germ cell mutations can lead to hereditary damage. Depending on the extent of the change (single or multiple genes, larger chromosome segments or complete chromosomes), a distinction is made between point and block mutations as well as numerical and structural chromosomal aberrations.

MYCN syn. MYCN oncogene
stands for MYCN oncogene, a carcinogenic gene that can be detected in various types of tumours, such as some neuroblastomas and medulloblastomas; tumour cells harbouring the MYCN oncogene are particularly resistant to chemotherapy and radiotherapy.

MYCN amplification
duplification of the MYCN oncogene, a cancer-causing gene that can be detected in various types of tumours (for example, some neuroblastomas and medulloblastomas); amplification of oncogenes (such as MYCN) is associated with the development and/or spread of some tumors. Tumor cells with the MYCN oncogene are particularly resistant to chemotherapy and radiotherapy.