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The typical contrast is between a highly cellular, relatively scantily supported encephaloid cancer and a fibroplastic growth composed predominantly of elongated cells and developing fibrous material. Neither historical name is a complete modern tumour classification.

In encephaloid cancer, a thin preparation from a viable region shows crowded, variably sized cells, often rounded, oval, polygonal or irregular, with conspicuous cell nuclei and a prominent cell nucleolus. Some cells have more than one cell nucleus; the cytoplasm and nuclear proportions vary. In sections, the cells form masses or groups separated by a comparatively delicate vascular stroma. Where the lesion is a carcinoma, cohesive epithelial arrangements and invasion of surrounding tissue help establish its nature. The scant support helps explain the soft, brain-like gross consistency denoted by “encephaloid”; it does not mean that the growth is made of brain tissue.

A rapidly growing soft tumour may also show evidence of mitosis, haemorrhage, necrosis and granular or fatty cellular debris. These features vary with sampling and are not the definition of every historical encephaloid lesion. The viable advancing edge is more informative about cell type and invasion than a completely broken-down centre. A modern interpretation combines architecture, cell morphology and, where needed, immunohistochemistry; one large nucleolated cell is not a universal “cancer corpuscle.”^[ref][ref]

In a typical fibroplastic growth, the conspicuous elements are oval or spindle-shaped cells, with elongated cell nuclei, tapering processes and intercellular material taking on a fibrillar character. The cells may run in parallel bundles or interlacing groups. Some areas contain many apparently free oval cell nuclei; other areas show more mature fibres and fewer obvious cell bodies. A teased preparation helps display individual elongated cells and fibres, whereas a section shows how the bundles relate to vessels and surrounding tissue.

The historical interpretation was of a growth resembling developing connective tissue. It should not be translated automatically into either a harmless fibroma or a specific modern fibrosarcoma. Contemporary descriptions recorded recurrence and malignant behaviour in some growths put in this broad category.^[ref] Cell shape must be read with tissue architecture and behaviour. Apparent resemblance to fibroblasts does not establish benignity, and a scant-fibred soft growth is not by itself proof of epithelial origin.

Examine the whole body before disturbing the wound, recording its situation, dimensions, margins and relation to damaged blood vessels. Then expose the wound track by careful dissection. An injury received while the blood circulation was active may show substantial hemorrhage, blood infiltrating the surrounding tissue, and adherent blood clots. Infiltration is more informative than loose blood merely lying on the surface: serial cuts can show whether blood has penetrated the tissue rather than simply coated it.

The interval of survival changes what can reasonably be expected. If the person survived long enough, surrounding inflammation, cellular reaction, formation of granulation tissue, or an established scar is evidence of a process that began during life. Such findings can make the conclusion much stronger than the appearance of a fresh cut. They do not furnish a universal clock: wound healing varies with site, severity, health and environment.

A post-mortem cut will often have relatively pale margins and little infiltration, although it can gape because skin and other tissues are elastic. Blood may still escape from a recently dead body, particularly from dependent or congested parts, and coagulation can occur around the time of death. Livor mortis can resemble bruising, while drying and putrefaction alter colour and consistency. A body moved, compressed or subjected to attempts at resuscitation presents further opportunities for artefact. Therefore neither “it bled” nor “the edges retracted” establishes that the wound was inflicted during life.

For modern corroboration, sample the margin, underlying tissue and an uninjured comparison site for histology, interpreting inflammation and other markers in the context of the whole examination. A primary study of decomposed forensic cases illustrates the use of immunohistochemistry while explicitly warning that extravasated red blood cells alone do not reliably establish wound vitality.^[ref]

Consequently, a rapidly fatal wound may be impossible to distinguish confidently from one inflicted immediately after death by gross aspect alone. Absence of developed inflammation is expected when survival was extremely brief; it is not proof of post-mortem injury. The answer should express the degree of support, rather than force an unwarranted yes-or-no conclusion.

The quotation marks around “Malignant” matter. In 1867 the clinical grouping did not have a single settled boundary in histology. Infiltration, destructive growth, return after removal, spread to distant sites and progressive constitutional illness were warning features; hardness or rapid growth alone was not a sufficient definition. A contemporary review of an 1866 textbook explicitly disputed confused descriptions of hard and soft cancer, illustrating that this was already a live diagnostic controversy.^[ref]

A useful period classification, without pretending that every contemporary author drew the same boundaries, is:

Those are overlapping historical descriptive groups, not six mutually exclusive modern diagnoses. Nor does every growth historically called “sarcoma” meet the modern definition of sarcoma.

The modern organising principle asks what cells are malignant. Carcinoma arises from epithelium; sarcoma arises in bone or soft tissue; melanoma arises from melanocytes; lymphoma and leukaemia concern blood-forming or immune cells. Other families include central nervous system and germ cell tumours. A solid lump is not essential for cancer. Within a family, histology, immunohistochemistry and appropriate molecular diagnostics refine the diagnosis. Tumour grade describes features of aggressiveness, whereas tumour stage describes extent of disease.^[ref]

This also corrects the old inference that recurrence must reflect a mysterious constitutional deposit: local residual disease and metastasis are distinct mechanisms, and an apparently circumscribed growth may already have disseminated.

Original research, Frontiers in Medicine 8:802841, published 24 December 2021. A pilot study of immunohistochemistry in decomposed forensic material; the authors describe its conclusions as inconclusive and advocate combined markers.