Benign vs. Malignant Tumors

Benign Tumor

A slow-growing, well-circumscribed neoplasm that does not invade or metastasize; usually well-differentiated.

Malignant Tumor

A rapidly-growing, infiltrative tumor capable of invading tissues and metastasizing; often poorly differentiated.

Metastasis

Spread of tumor cells to a discontinuous site; the most definitive sign of malignancy.

Differentiation

Degree to which tumor cells resemble the normal tissue of origin.

Anaplasia

Complete lack of differentiation; a hallmark of malignancy.

Pleomorphism

Variation in size and shape of tumor cells and their nuclei.

Hyperchromasia

Dark-staining nuclei due to increased DNA content; seen in malignant cells.

Increased Nuclear:Cytoplasmic Ratio

Malignant cells often have large nuclei that occupy most of the cell's volume.

Coarse Chromatin

Abnormal clumping of nuclear chromatin; common in malignant cells.

Atypical Mitoses

Irregular mitotic figures (e.g., tripolar or multipolar) seen in malignancy.

Loss of Polarity

Disruption of normal nuclear alignment relative to the basement membrane in epithelial tissues.

Tumor Necrosis

Ischemic death of tumor cells due to rapid growth outpacing blood supply; common in malignancy.

Encapsulation

Feature of benign tumors; presence of a fibrous capsule separating the tumor from normal tissue.