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Neoplasia

NEOPLASIA Definition The term neoplasia literally means “new growth.” A neoplasm (tumor) is an abnormal mass of tissue that grows excessively and uncoordinatedly compared to normal tissues, and persists even after the removal of the stimulus which caused it. Basic Concepts Neoplasia arises due to genetic mutations that lead to uncontrolled cell proliferation. These mutations affect genes controlling: Cell growth and differentiation Apoptosis (programmed cell death) DNA repair mechanisms Terminology Term Meaning Tumor Any swelling or mass; now commonly used for neoplasms Oncology Study of tumors (from oncos = tumor, logos = study) Benign Tumor Localized, non-invasive, slow-growing Malignant Tumor (Cancer) Invades, destroys tissue, and metastasizes Classification 1. Based on Behavior Type Characteristics Example Benign Slow-growing, well-differentiated, non-invasive Lipoma, Adenoma Malignant Rapid growth, poorly differentiated, invasive, metastasizing Carcinoma, Sarcoma 2. Based on Tissue of Origin Tissue Benign Tumor Malignant Tumor Epithelial Adenoma, Papilloma Carcinoma Mesenchymal Lipoma, Fibroma Sarcoma Lymphoid — Lymphoma Hematopoietic — Leukemia Microscopic Features of Neoplasia Microscopic pattern Differentiation & Anaplasia Differentiation = how closely tumor cells resemble normal cells. Anaplasia = loss of cellular differentiation → hallmark of malignancy. Tumor Angiogenesis & Stroma Inflammatory Reaction Characteristics of Malignant Tumors Anaplasia (loss of structure & function) Rapid growth Invasion into surrounding tissues Metastasis (spread to distant sites) Abnormal mitotic figures Loss of contact inhibition Metastasis The spread of tumor cells from the primary site to distant locations. Common routes: Lymphatic spread – typical of carcinomas Hematogenous spread – typical of sarcomas Seeding in body cavities – e.g., ovarian carcinoma in peritoneum Causes of Neoplasia Cause Examples Genetic mutations Oncogenes, tumor suppressor gene mutations Chemical carcinogens Tobacco, aflatoxin Radiation UV, ionizing radiation Viral infections HPV, EBV, HBV Hormonal factors Estrogen in breast/endometrial carcinoma Diagnosis of Tumors Clinical Examination Histopathology (Biopsy) Cytology (FNAC, Pap smear) Immunohistochemistry Molecular tests (PCR, FISH, etc.) Grading and Staging Term Description Grading Degree of differentiation and aggressiveness of tumor cells (microscopic) Staging Extent of spread in the body (clinical + radiologic) TNM System T = Tumor size, N = Node involvement, M = Metastasis AJCC Staging: Stage 0–IV: Higher stage → more advanced cancer. Clinical Effects of Tumors Local destruction Compression of surrounding structures Hemorrhage, ulceration, infection Cachexia (wasting) Paraneoplastic syndromes Treatment Surgery Radiation therapy Chemotherapy Immunotherapy Targeted molecular therapy Summary Neoplasia is a process of uncontrolled, abnormal cell growth caused by genetic mutations. The outcome depends on the tumor’s behavior — benign tumors remain localized, while malignant ones invade and metastasize, causing significant morbidity and mortality.