Classification

Pediatric Tumours

Lecture № 5 Pediatric Tumours

Lesson 8

A tumor (American English) or tumour (British English) is commonly used as a synonym for a neoplasm (a solid or fluid-filled [cystic] lesion that may or may not be formed by an abnormal growth of neoplastic cells) that appears enlarged in size. Tumor is not synonymous with cancer. While cancer is by definition malignant, a tumor can be benign, premalignant, or malignant.

The terms "mass" and "nodule" are often used synonymously with "tumor". Generally speaking, however, the term "tumor" is used generically, without reference to the physical size of the lesion. More specifically, the term "mass" is often used when the lesion has a maximal diameter of at least 20 millimeters (mm) in greatest direction, while the term "nodule" is usually used when the size of the lesion is less than 20 mm in its greatest dimension (25.4 mm = 1 inch).

Tumor can be classified:

o benign,

o premalignant, or

o malignant.

The principal behavioristic characteristics of benign and malignant neoplasms are as follows:

The majority of the differences between benign and malignant neoplasms are relative. The critical difference between the two types is point # 7, in that benign neoplasms by definition do not exhibit metastatic growth, whereas all malignant neoplasms have the potential for successful metastatic growth. A metastasis is defined as the secondary growth of a neoplasm, originating from a primary neoplasm and growing within the host organism in a location distant from the initial or primary site of neoplastic growth.

Histogenetic Classification

Although the behavioristic classification is one of the most commonly accepted segments of the nomenclature of neoplasms, the most important principle in the classification of neoplasms is their grouping according to the type of tissue from which the neoplasm has arisen:

1. Epithelium

2. Connective tissue

3. Hemopoietic and immune systems

4. Nervous system

5. Multiple histogenetic cellular origin

6. Miscellaneous

It is very important to determine the region, origin, or tissue from which the neoplasm arose.

In addition, other descriptive terms are often utilized in classifying or diagnosing a specific problem. Such descriptive terms as papillary, cystic, follicular, and others may relate to various histological characteristics of neoplasms of epithelial origin.

Some neoplasms have been named according to the individual first describing the lesion; examples are Ewing tumor of bone, Hodgkin disease of lymph tissue, and Wilms’ tumor of the kidney.