Benign neoplasia including nomenclature and characteristics of Benign & Malignant Tumours

Neoplasia

An abnormal mass of tissue with uncontrolled uncoordinated irreversible proliferation that persists after the initiating stimulus is removed

Benign tumour

A localized slow-growing well-differentiated non-invasive tumour that does not metastasize

Malignant tumour

A rapidly growing invasive tumour capable of metastasis and tissue destruction

Most important feature distinguishing benign from malignant tumours

Metastasis

Leiomyoma

A benign tumour of smooth muscle origin commonly occurring in the uterus

Leiomyosarcoma

A malignant tumour of smooth muscle origin

Basal cell carcinoma

A locally invasive malignant skin tumour commonly occurring on the nose that rarely metastasizes

Rodent ulcer

A basal cell carcinoma with rolled heaped-up margins and central ulceration

Heaped up ulcer margins

Classic gross feature suggesting malignancy

Punched out ulcer

Gross feature more suggestive of a benign ulcer

Common site of basal cell carcinoma

Nose and sun-exposed skin

Fibrosis

Healing by scar tissue deposition commonly seen in cirrhosis

Cirrhosis

Chronic liver disease characterized by fibrosis and regenerative nodules

Benign tumour growth

Slow expansive and often encapsulated

Malignant tumour growth

Rapid infiltrative and destructive

Encapsulation

Feature commonly present in benign tumours but absent in malignant tumours

Differentiation

Degree to which tumour cells resemble the normal tissue of origin

Well-differentiated tumour

Tumour closely resembling the parent tissue with better prognosis

Poorly differentiated tumour

Tumour showing marked atypia and little resemblance to the parent tissue

Anaplasia

Complete lack of differentiation seen in aggressive malignant tumours

Pleomorphism

Variation in size and shape of cells and nuclei characteristic of malignancy

Hyperchromasia

Darkly staining nuclei due to excess nuclear DNA seen in malignant cells

Increased N:C ratio

Nuclear to cytoplasmic ratio approaching 1:1 typical of malignant cells

Atypical mitoses

Abnormal mitotic figures indicating malignancy

Necrosis in tumours

Common in rapidly growing malignant tumours due to inadequate blood supply

Parenchyma

The proliferating neoplastic cells that determine tumour behaviour

Stroma

Supportive connective tissue and blood vessels within a tumour

Less tumour stroma

More tumour necrosis due to inadequate vascular support

Papilloma

A benign epithelial tumour producing finger-like projections

Adenoma

A benign epithelial tumour forming glandular patterns

Adenocarcinoma

A malignant epithelial tumour with glandular differentiation

Fibroma

A benign tumour of fibrous tissue

Fibrosarcoma

A malignant tumour of fibrous tissue

Lipoma

A benign tumour of adipose tissue

Liposarcoma

A malignant tumour of adipose tissue

Osteoma

A benign bone tumour

Osteosarcoma

A malignant bone-forming tumour

Chondroma

A benign cartilage tumour

Chondrosarcoma

A malignant cartilage tumour

Polyp

A projection above a mucosal surface usually benign

Teratoma

A tumour arising from more than one germ cell layer

Melanoma

A malignant tumour of melanocytes despite the benign-sounding suffix “-oma”

Glioma

A tumour of glial cells that is usually malignant despite the suffix “-oma”

Seminoma

A malignant germ cell tumour of the testis

Leukaemia

A malignant neoplasm of haematopoietic cells involving bone marrow and blood

Lymphoma

A malignant tumour of lymphoid tissue

Metastasis

Formation of secondary tumour deposits discontinuous from the primary tumour

Most definitive evidence of malignancy

Metastasis

Lymphatic spread

Main pathway of spread for carcinomas

Haematogenous spread

Main pathway of spread for sarcomas

Transcoelomic spread

Tumour seeding across body cavities such as the peritoneum

Example of transcoelomic spread

Ovarian carcinoma seeding the peritoneum

Tumour progression

Accumulation of mutations leading to increasingly aggressive tumour behaviour

Multistep carcinogenesis

Sequential accumulation of genetic damage transforming normal cells into malignant cells

Sequence of carcinogenesis

Normal cell → metaplasia → dysplasia → anaplasia → invasion → metastasis

Non-lethal genetic damage

Central underlying mechanism of carcinogenesis

Proto-oncogene

A normal growth-promoting gene that can become an oncogene when mutated

Oncogene

A mutated gene promoting uncontrolled cellular proliferation

Tumour suppressor gene

A gene that inhibits cell growth and prevents neoplasia

p53

Tumour suppressor protein called the guardian of the genome that arrests the cell cycle after DNA damage

Main function of p53

Stops the cell cycle and induces apoptosis after DNA damage

Rb

Tumour suppressor protein regulating the G1 to S phase transition in the cell cycle

APC

Tumour suppressor gene commonly mutated in tubular adenomas and familial adenomatous polyposis

Tubular adenoma mutation

Most commonly associated with APC mutation

KRAS

Oncogene involved in signalling pathways promoting cell proliferation

MLH1

DNA mismatch repair gene associated with Lynch syndrome

Cyclins

Proteins that regulate progression through the cell cycle

CDKs

Cyclin-dependent kinases that drive cell cycle progression

Immune surveillance

Recognition and destruction of tumour cells by the immune system

Mechanism of immune surveillance

T-cell activation due to tumour antigen presentation

PD-L1

Immune checkpoint protein targeted by monoclonal antibody therapy in metastatic cancers including NSCLC

Immune checkpoint inhibitors

Therapies blocking PD-L1 or PD-1 to enhance anti-tumour T-cell activity

Hyperplasia

Controlled reversible increase in cell number

Hypertrophy

Increase in cell size causing organ enlargement

Metaplasia

Reversible replacement of one mature cell type by another mature cell type

Dysplasia

Disordered cellular growth with atypia and loss of uniformity that may progress to cancer

Invasion

Direct infiltration and destruction of surrounding tissues by malignant cells

Basement membrane invasion

Key histological feature distinguishing invasive carcinoma from carcinoma in situ

Carcinoma

A malignant tumour of epithelial origin

Sarcoma

A malignant tumour of mesenchymal origin

Carcinomas spread mainly by

Lymphatics

Sarcomas spread mainly by

Blood vessels

Most common molecular target in checkpoint immunotherapy

PD-L1

Most important tumour suppressor in DNA damage response

p53

Classic benign smooth muscle tumour

Leiomyoma

Classic malignant smooth muscle tumour

Leiomyosarcoma

Most likely malignant feature in an ulcer

Heaped up margins

Healing process most associated with cirrhosis

Fibrosis