Introduction to Neoplasia

1. Benign Neoplasms
2. Malignant Neoplasms
3. Nomenclature of Neoplasms
4. Eponyms
5. In-situ and Invasive Carcinomas
6. Staging and Grading of Tumours
7. Cancer Screening
8. Quiz

• Tumours are clinically detectable masses or swellings, which may be neoplastic or non-neoplastic in origin.
• Benign neoplasms are non-invasive and well circumscribed, and under the microscope the cells appear well differentiated.
• Malignant neoplasms invade surrounding tissue and may spread to distant sites. Their microscopic appearance varies: well-differentiated cancers can resemble their tissue of origin, whereas poorly differentiated tumours may show little resemblance, marked nuclear atypia and abnormal mitoses.
• Grading is used to determine the behaviour of the malignancy, and staging illustrates the growth.
• Screening can be used to detect early cervical, bowel and breast cancers.

Any nucleated cell has the potential to form a neoplasm - an abnormal growth of cells that persists after the stimulus is removed. This happens through accumulation of genetic alterations that change the appearance and behaviour of the cell. Tumours are any clinically detectable lump or swelling, and can be defined as either neoplastic or non-neoplastic.

Neoplasms are classified according to their behaviours and morphology. Broadly they can be classified into benign and malignant. Malignant neoplasms are commonly known as cancers.

Benign Neoplasms

This type of tumour is non-invasive and remains confined to its site of origin. They are often well circumscribed and may be encapsulated by a thin layer of connective tissue, with a pushing outer margin. Under the microscope the cells are typically well differentiated and resemble the tissue from which it originates.

Diagram - The growth of a benign neoplasm. It is regular and well circumscribed

SimpleMed original by Dr. Emily Smith

Image - A benign neoplasm under the microscope. The cells show nuclear changes, but still resemble the original tissue

Creative commons source by No machine-readable author provided. KGH assumed (based on copyright claims). [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/)]

Malignant Neoplasms

The ability to invade surrounding tissues and spread to different sites (metastasise) are key defining factors of malignant neoplasms. They often grow more rapidly than benign tumours and may have irregular edges, no clear margin, with invasion into surrounding tissues. This type of neoplasm often has central necrosis due to inadequate perfusion when it outgrows its blood supply.

The degree of differentiation varies between malignant tumours. Well-differentiated cancers retain features of their tissue of origin; poorly differentiated tumours may show little resemblance. Atypical nuclei may show enlargement, hyperchromasia (dark staining), chromatin clumping and variation in size and shape (pleomorphism). Increased or abnormal mitotic figures can also be present. These findings support diagnosis but are not universal features of every cancer.

Diagram - The growth of a malignant neoplasm. It is invading into the surrounding tissues, giving it an irregular edge. The tumour is growing fast, resulting in ulceration and areas of necrosis

SimpleMed original by Dr. Emily Smith

Image - A malignant peripheral nerve sheath tumour under the microscope. This example illustrates abnormal spindle-cell morphology; malignant tumours vary in their resemblance to normal tissue.

Creative commons source by Nephron [CC BY-SA 3.0 (https://creativecommons.org/licenses/by-sa/3.0)]

Table - Differences between benign and malignant neoplasms

SimpleMed original by Dr. Emily Smith

Nomenclature of Tumours (Tumour naming)

The naming of tumours often depends on the origin tissue, and whether the tumour is benign or malignant.

Epithelial Tumours

• Benign Tumours
  • Benign tumours of epithelium are classified as either a papilloma or an adenoma and require the name of the tissue or cell it originates from. 
  • A papilloma is a benign tumour of non-glandular epithelium and is prefixed by the cell type, e.g. stratified squamous papilloma.
  • An adenoma is a benign tumour of glandular epithelium e.g. colonic adenomas.
• Malignant Tumours
  • A malignant tumour of non-glandular epithelium is called a carcinoma prefixed by the cell type e.g. squamous cell carcinoma.
  • A malignant tumour of glandular epithelium is called an adenocarcinoma, e.g. colonic adenocarcinoma.
    

Connective Tissue Tumours

• These tumours have a prefix associated with each tissue as shown in the table below, for example cartilage has the prefix ‘chondro-‘.
• Benign
  • This type of tumour has the suffix ‘-oma’.
• Malignant
  • This type of tumour has the suffix ‘-sarcoma’.

Table - Nomenclature of benign and malignant tumours

SimpleMed original by Dr. Emily Smith

Eponyms

Despite these rules of nomenclature, there are some tumours which don’t follow them. These tumours are often named after a person.

• Burkitt’s lymphoma - a type of B cell lymphoma
• Hodgkin’s lymphoma - malignant lymphoma
• Ewing’s sarcoma - malignant neoplasm of bone
• Kaposi’s sarcoma - malignant neoplasm of vascular endothelium

Preview the Introduction to Neoplasia quiz