Neoplasia: Definition and Risk Factors

Neoplasia Definition and Risk Factors

• Neoplasia is an uncontrolled abnormal growth of cells or tissues in the body.
• Risk factors include:
  • Genetic predisposition: inherited genetic mutations or familial cancer syndromes.
  • Environmental exposures: exposure to carcinogenic agents, such as tobacco smoke, UV radiation, and ionizing radiation.
  • Infectious agents: chronic infections with certain viruses, bacteria, or parasites, such as HPV and cervical cancer.
  • Age and gender: advancing age is a significant risk factor, with most cancers increasing with age.

Cellular Characteristics of Malignant Neoplasms

• Variation in size
• High N/C ratio
• Cellular pleomorphism
• Nuclear pleomorphism
• High mitotic activity
• High chromatin nucleus
• Loss of polarity

Neoplasia Behavior and Classification

• Benign: well-differentiated, locally non-invasive, and non-metastatic.
• Malignant: moderately differentiated, locally invasive, and metastatic.

Types of Neoplasms

Benign Neoplasms

• Connective tissue:
  • Lipoma (adipose tissue)
  • Fibroma (fibrous tissue)
  • Chondroma (cartilage)
  • Osteoma (bone tissue)
• Epithelial tissue:
  • Papilloma (surface epithelium)
  • Adenoma (glandular epithelium)

Malignant Neoplasms

• Connective tissue:
  • Sarcoma (e.g. liposarcoma, fibrosarcoma, chondrosarcoma, osteosarcoma)
• Epithelial tissue:
  • Carcinoma (e.g. squamous cell carcinoma, basal cell carcinoma, adenocarcinoma)

Specific Types of Neoplasms

Squamous Cell Papilloma

• Benign nature
• Papillary architecture
• Koilocytosis: presence of enlarged, irregularly shaped squamous epithelial cells with perinuclear halos, often indicative of HPV infection.

Columnar Cell Papilloma

• Typically found in the subareolar region of the breast, particularly in the large lactiferous ducts near the nipple.

Follicular Thyroid Adenoma

• Encapsulation: surrounded by a fibrous capsule that separates them from the surrounding thyroid tissue.
• Causes: iodine deficiency, radiation exposure.

Fibroadenoma

• Benign breast tumors
• Composed of both glandular and fibrous tissue
• Causes: hormonal influence (estrogen and other hormonal factors)

Cystadenoma

• Benign cystic tumors
• Arise from glandular epithelial cells
• Characterized by the presence of cystic spaces filled with fluid (usually serous fluid)

Neurofibroma

• Originate from Schwann cells
• Distributed along peripheral nerves throughout the body
• Can be benign or malignant (neurofibrosarcoma)

Lipoma

• Benign
• Well-bounded
• Non-invasive
• Closely resembles the tissue of origin (fat)

Basal Cell Carcinoma

• Typically begins as a nodule, progresses to ulceration or crusting, and may subsequently invade deeper layers of the skin if left untreated.
• Causes: UV radiation exposure.

Squamous Cell Carcinoma

• Often exhibits keratinization
• Potential for metastasis
• Causes: UV radiation exposure, chronic skin damage.

Adenocarcinoma

• Causes: chronic inflammation, prolonged exposure to irritants, infections, or inflammatory conditions.
• Examples: colon adenocarcinoma, pancreatic adenocarcinoma.

Osteosarcoma

• Often causes extensive destruction of the affected bone
• Causes: bone dysplasias and growth disorders, such as hereditary multiple exostoses (osteochondromatosis).