Benign tumors

Benign Neoplasms: Overview

  • Definition: Benign neoplasms are non-cancerous growths. They do not invade surrounding tissues or metastasize.

General Principles

  • Types of benign neoplasms include:

    • Papilloma

    • Polyp

    • Fibroadenoma of the breast

    • Uterine leiomyoma

    • Hemangioma

    • Pleomorphic adenoma / Mixed tumor of parotid gland

    • Mature teratoma of the ovary

Characteristics

  • Nomenclature:

    • Benign tumors often end with -oma (e.g., adenoma, papilloma).

    • Malignant tumors typically end with -carcinoma (epithelial origin) or -sarcoma (mesenchymal origin).

    • Notable exceptions: melanoma and lymphoma are malignant but end with -oma.

  • Clarification: Neoplasia refers to abnormal, excessive cellular growth resembling the tissue of origin, not necessarily cancer.

Histogenesis (Origin of Tumors)

  • Epithelial: -adenoma / -carcinoma

  • Mesenchymal: -fibroma / -sarcoma

  • Lymphocytic: pseudolymphoma / -lymphoma

  • Melanocytic: nevus / melanoma

  • Neural: neurofibroma / schwannoma / malignant peripheral nerve sheath tumor

  • Glial: astrocytoma (malignant)

  • Mixed tumors: adenofibroma / carcinosarcoma / adenosarcoma (benign epithelial with malignant mesenchymal component)

Gross Features of Benign Tumors

  • Characteristics:

    • Encapsulated

    • Well demarcated

    • Slow-growing

    • Compress adjacent tissues without invading

    • Do not cause tissue damage

    • Are cured by surgical removal or surveillance.

Microscopic Features

  • Organized growth

  • Well differentiated cellular elements

  • Absence of atypical mitoses and nuclear atypia

  • Uniform nuclei with low nuclear-cytoplasmic ratio

  • No invasion of surrounding tissues.

International Classification of Diseases (ICD-10)

  • D12: Benign tumors

  • D37: Uncertain behavior (benign or malignant)

  • Specific codes exist for various tumors (e.g., carcinoid).

Benign vs. Malignant Tumors

  • Benign: Excessive proliferation, single mass.

  • Malignant: Cancer that invades surrounding tissue.

    • Classifications include carcinomas, sarcomas, and others.

Choristoma vs. Hamartoma

  • Choristoma: Pseudotumoral growth made of ectopic tissue (normal tissue in abnormal location).

  • Hamartoma: Native cells with disorganized disposition, normal growth rate (e.g., chondroma).

Papilloma

Overview

  • Definition: Benign tumor of the squamous epithelium; can exist in various locations (cervix, vagina, skin, etc.).

    • Types:

      • Sessile: Broader base, grows parallel to surface.

      • Pedunculated: Narrow base, grows perpendicular to surface.

Gross Features

  • Exophytic, firm consistency proportional to keratinization, rough surface, size < 1.5 cm.

Microscopic Features

  • Acanthosis: Hyperplasia of the spinous layer.

  • Hyperkeratosis: Thickening of the stratum corneum.

  • Papillomatosis: Finger-like projections from dermal papillae.

  • Inflammatory infiltrate in the papillary dermis.

Differential Diagnosis of Papilloma

  • 1. Seborrheic Keratosis:

    • Exophytic, pigmented, firm texture, located on scalp/trunk/face.

  • 2. Verruca Vulgaris:

    • Characterized by HPV-infected cells (koilocytes).

Polyp

  • Definition: Exophytic proliferation of glandular epithelium, found in various organs such as:

    • Gastrointestinal tract (colon, stomach)

    • Uterine cavity (endometrial polyp)

    • Cervix (endocervical polyp)

Types of Colonic Polyps

  • Adenomatous Polyps: Always associated with dysplasia (tubular, villous, tubulovillous).

  • Hyperplastic Polyps: Generally no dysplasia.

  • Hamartomatous Polyps: Associated with conditions like Peutz-Jeghers syndrome.

Fibroadenoma of the Breast

Overview

  • Definition: Most common benign tumor in fertile women, composed of glandular epithelium and stroma.

Features

  • Tumor is solid, painless, mobile, usually < 3 cm, may appear gray-white, elastic, and well-defined.

Microscopy

  • Both epithelial and stromal components proliferate; subtypes include:

    • Intracanalicular: Compressed glands.

    • Pericanalicular: Glands with open lumens.

Leiomyoma of the Uterus

Definition

  • Most common benign tumor in the uterine corpus with proliferation of smooth muscle.

Clinical Features

  • Can be asymptomatic, or may cause abnormal bleeding, pain, or infertility.

Gross Features

  • Nodular, well-demarcated tumors, frequently multiple with a whorled appearance.

Microscopy

  • Fascicular smooth muscle bundles with distinct cell membranes and spindle-shaped nuclei.

Hemangioma

Definition

  • Benign tumor of proliferated blood vessels; can affect various organs.

Types

  • Congenital Hemangioma: Present at birth, may involute.

  • Juvenile Hemangioma: Growth post-birth, eventual involution.

  • Cavernous Hemangioma: Large dilated vessels, often found in the liver.

Gross Features

  • Red-purple color, elastic consistency, can be flat or papular.

Microscopy

  • Unencapsulated, thin-walled capillaries lined by bland endothelial cells with red blood cells present.

Mature Teratoma

Definition

  • Benign tumor containing cells from two or more germ layers. Common in young women.

Gross Features

  • Large cysts filled with greasy, yellowish content, possibly containing teeth and hair.

Microscopy

  • Covered by ectodermal structures, with mesodermal and endodermal elements present.

Pleomorphic Adenoma / Mixed Tumor of Parotid

  • Definition: A benign tumor composed of both epithelial and mesenchymal (stromal) elements, primarily found in the parotid gland.

  • Characteristics:

    • Can exhibit varied histological features, such as cartilage-like areas and different cellular types.

    • Often slow-growing and well-circumscribed.

  • Clinical Presentation: Typically presents as a painless mass in the parotid region, common in adults, especially females.

  • Microscopy: Features a mix of cell types, including ductal epithelial cells and myoepithelial cells, within a stromal background that may appear chondroid or myxoid.

  • Treatment: Surgical excision is the standard management, with careful removal to prevent recurrence.