Neoplasia is new growth. The terms benign and malignant correlate to the course of the neoplasm. Benign neoplasms stay localized in one place; malignant neoplasms invade surrounding tissue and, in most cases, can metastasize to distant organs. To become neoplastic, a normal cell must develop mutations that allow it to no longer obey boundaries of adjacent cells, thus allowing for uncontrolled growth, and the neoplasm must be able to produce its own blood supply. If the neoplasm is malignant, the cells must also gain the ability to invade the basement membrane and surrounding tissue, enter the blood stream, and spread to and grow within distant organs.
This chapter will discuss the basic terms associated with neoplasia, features used to distinguish benign neoplasms from malignant neoplasms, epidemiology and etiology of neoplasms, effects of tumors (including paraneoplastic syndromes), basic carcinogenesis (including proto-oncogenes and tumor suppressor genes), diagnosis (including tumor markers and immunohistochemistry), and basic grading and staging.
Overview: The terms tumor, nodule, and mass are nonspecific terms that refer to an abnormal proliferation of cells. The term neoplasm means new growth and does not imply benign or malignant (i.e., there are benign neoplasms, and there are malignant neoplasms).
Nomenclature for general categories of neoplasms
- Adenoma: Benign neoplasm derived from glandular cells.
- Carcinoma: Malignant neoplasm derived from epithelial cells (Figures 4-1 and 4-2).
- Sarcoma: Malignant neoplasm derived from mesenchymal cells (e.g., fat, muscle).
- Lymphoma: Malignant neoplasm derived from lymphocytes.
- Melanoma: Malignant neoplasm derived from melanocytes.
- Germ cell tumor: Malignant neoplasm derived from germ cells.
Squamous cell carcinoma. Squamous cell carcinoma is one of the major forms of carcinoma, occurring within many organs including the mouth, upper respiratory tract, and lungs. In the center of the photomicrograph is a keratin pearl, a characteristic feature of a well or moderately differentiated squamous cell carcinoma. Hematoxylin and eosin, 400×.
Prostatic adenocarcinoma. Adenocarcinoma is one of the major forms of carcinoma. In well and moderately differentiated forms, the glandular histology is readily apparent (as in this section). Hematoxylin and eosin, 400×.
Nomenclature for benign neoplasms
In general, the name of a benign neoplasm often ends with –oma.
- Examples: Adenoma (benign neoplasm of glandular epithelium), fibroadenoma (benign neoplasm of the breast), and leiomyoma (benign neoplasm of smooth muscle).
- Some exceptions: Hepatoma (malignant neoplasm of liver), melanoma (malignant neoplasm of melanocytes), mesothelioma (malignant neoplasm of mesothelial cells), and seminoma (malignant germ cell neoplasm of testis).
Nomenclature for malignant neoplasms
In general, the name of a malignant neoplasm often ends with –carcinoma or –sarcoma.
- Examples: Adenocarcinoma (malignant neoplasm of glandular tissue), rhabdomyosarcoma (malignant neoplasm of skeletal muscle), and leiomyosarcoma (malignant neoplasm of smooth muscle)....