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Researcher in immunotherapy. Richard A. Morgan and collaborators reported a serious adverse event after engineered T-cell administration, documenting why target recognition must be assessed in healthy tissues as well as tumours.^[ref]

A malignant tumour with mesenchymal differentiation, including cancers of bone and soft tissues. It differs from epithelial carcinoma in cellular lineage rather than simply in anatomical depth.

A tumour-graft model using a genetically compatible host and donor, enabling investigation in an immune-competent setting. It generally uses mouse rather than human tumour biological cells.

A tumour arising in the testis. Germ-cell and other cellular origins produce different categories, so location alone does not determine histology or malignant potential.

The gene encoding the p53 regulatory protein, frequently altered in tumours. Different alleles can cause loss of function, dominant-negative effects or additional context-dependent effects.

Tumor necrosis factor, abbreviated TNF and also called TNF-alpha, is a signalling cytokine acting through cell-surface receptors. It occurs in membrane-associated and soluble forms, is produced prominently by macrophages, and can induce cell death in susceptible tumour cells. The biological outcome depends on the responding cells and signalling context.^[ref]

Its name records an experimental discovery. In1975, investigators found that blood serum from mice first infected with BCG and then treated with endotoxin could cause necrosis in transplanted tumours. Tests indicated that the active material was a host-derived factor, rather than residual endotoxin. The authors proposed release from macrophages; that proposed cellular origin should be distinguished from their directly observed serum activity.^[ref]

An illuminating comparison was the different response of cultures: the preparation was toxic to two tested neoplastic cell lines but not to mouse embryo cultures. This separates a measurable activity from a universal property of all cells. The historical tumour assay identified a signalling substance; it did not establish that TNF kills every tumour or has only one physiological role.^[ref]

An abnormal tissue mass. The term includes benign as well as malignant growths, so tumour and cancer are not always interchangeable.

Tumour angiogenesis is the growth of new blood vessels from pre-existing vessels in response to a tumour and its surrounding tissue. It supplies a route for oxygen and nutrients to reach growing cells. Vessel formation and effective perfusion are distinct: a vascular image alone does not measure the delivery of oxygen to every part of a tumour.

A foundational experiment by Judah Folkman, Ezio Merler, Charles Abernathy and Gretchen Williams tested tumour-derived material in a rat dorsal air sac assay. A membrane wick delivered separated material locally; after 48 hours the investigators inspected the vascular response with a stereoscope and took tissue sections. A wick without the active preparation provided a negative control. The response was graded from 0 to 5+, rather than measured as an absolute endothelial cell count.^[ref] This connected an isolated preparation to a reproducible biological effect. It did not identify a unique modern molecule or establish that inhibiting one signal would cure all cancers.

An original diffusion model explains why access to vessels matters. Approximate a vessel-free tumour as a sphere of radius $R$ with uniform oxygen consumption $q$ per unit volume per unit time. Let $D$ be a constant diffusion coefficient and fix the surface oxygen concentration at $C_s$. At steady state, the diffusion equation with consumption and spherical symmetry becomesFiniteness at the centre removes the singular integration term. Integrating again and imposing $C(R)=C_s$ givesIf a stipulated threshold $C_{\mathrm{crit}}$ is required to avoid hypoxia, the model predictsFor illustration, take $D=2\times 10^{-9}{\mathrm{m}}^2{\mathrm{s}}^{-1}$, $C_s-C_{\mathrm{crit}}=0.05\mathrm{mol}{\mathrm{m}}^{-3}$ and $q=0.01\mathrm{mol}{\mathrm{m}}^{-3}{\mathrm{s}}^{-1}$. The limiting radius is approximately $2.45\times 10^{-4}\mathrm{m}$, or $0.245\mathrm{mm}$. These are chosen model inputs, not measurements from the historical study or a universal size limit. Quadrupling consumption halves the limiting radius. A predicted negative concentration indicates failure of the assumed uniformly consuming viable sphere, not physically negative oxygen.

The calculation isolates a transport constraint; it does not model vessel branching, changing consumption or delivery by flowing blood. Signals such as vascular endothelial growth factor can influence endothelial cells, but their action and the resulting perfusion require biological measurements beyond this spherical model.

An antigen associated with malignant cells that can also be expressed in normal tissues. Association with a tumour is not proof of tumour-specific expression.

The organization of a tumour into related lineages sharing inherited changes. A clonal alteration need not be a causal driver because passengers can hitchhike during expansion.

A lymphocyte recovered from within a tumour specimen. Presence in a specimen does not alone establish effective recognition or killing of malignant cells.

The interval between a defined starting event and detection of tumour development under a specified assay. Detection threshold and competing causes of death affect interpretation.

The non-malignant cells, extracellular material, signals and physical conditions surrounding and interacting with a tumour. Its components can support or restrain progression depending on their state and context.

The number of somatic mutations per defined amount of tumour sequence under a specified assay. It is an imperfect proxy for the number of useful immunogenic targets.

The proportion of a sampled tumour preparation contributed by malignant biological cells. It affects interpretation of copy number, variant fractions and expression measurements.

A gene whose normal activity restrains tumour development. Loss-of-function alterations can be diverse, and allelic requirements vary among genes and contexts.

A benign smooth muscle tumour of the uterus, also called a leiomyoma. Effects depend partly on location: a small cavity-distorting lesion can have different consequences from a larger outward-growing one.^[ref]

Vascular endothelial growth factor, a family of signals that regulate vascular development and function, including angiogenic responses in tumours.

Coordinated tissue repair involving growth, migration, matrix remodelling and immune responses. Persistent deployment of related activities can support a tumour without constituting productive repair.

A graft transferred between species. Tumour xenografts test behaviour in the recipient setting, which may lack immune interactions present in the original host.