= Solution
\b[An historically appropriate classification distinguishes the hard, soft, gelatinous, pigmented and epithelial malignant growths, together with recurrent and destructive growths whose place in “cancer” was disputed. Modern classification instead distinguishes <tumours> by cellular lineage and biological behaviour.]
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.<Review of Demonstrations of Microscopic Anatomy (1866 book)>[Discussion under “tumours”, contrasting scirrhus with encephaloid, melanotic and colloid growths and rejecting an indiscriminate use of “cancer”]{ref}
A useful period classification, without pretending that every contemporary author drew the same boundaries, is:
* \b[<Scirrhous carcinoma>, or hard <cancer>.] Abundant firm fibrous supporting tissue makes a hard, often contracted growth, classically in the <breast>. Retraction and fixation reflect invasion and contraction of that supporting tissue. “Hard” describes the gross appearance; it is not a separate modern cellular lineage.
* \b[<Encephaloid cancer>, or medullary/soft <cancer>.] The name refers to soft, brain-like tissue, often richly cellular and prone to rapid growth, breakdown and <haemorrhage>. The historical label could include more than one modern diagnosis; it does not mean a <tumour> of the <brain>.
* \b[<Colloid cancer>.] A gelatinous appearance associated with abundant <mucin>. Some such lesions would now be classified as <mucinous carcinomas>; appearance alone cannot retrospectively determine their modern identity.
* \b[<Melanotic tumour>.] Dark pigment supplied a gross category. Many malignant examples belong to modern <melanoma>, arising from <melanocytes>, but pigmentation is neither necessary nor sufficient for <melanoma>. Pigmented examples could also be treated as varieties within other period categories.
* \b[<Epithelioma>, or epithelial <cancer>.] A growth exhibiting epithelial structure, especially at <skin> and <mucous membrane> surfaces. Many examples correspond to <squamous cell carcinoma>. A locally destructive <rodent ulcer>, now generally <basal cell carcinoma>, was sometimes separated because distant spread was unusual.
* \b[<Recurrent fibroid tumour> and related “fibroplastic” or other <sarcomas>.] These could return repeatedly and invade locally despite differing from the period's typical <cancer>. They were sometimes called semi-malignant. A reported 1866 <recurrent fibroid tumour> developed distant deposits after apparently successful local treatment: a vivid reason that a purely local category could fail.<St George's Hospital Reports (1866)>[Case of recurrent fibroid tumour of the thigh, subsequent constitutional disease and post-mortem deposits; terminology is the report's historical terminology]{ref}
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.<What Is Cancer? by the National Cancer Institute>[“Types of Cancer”, especially carcinoma, sarcoma, leukaemia, lymphoma, melanoma and other tumour types]{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.
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