The basic components of a tumor are the parenchyma and stroma.
— The parenchyma comprises the neoplastic cells.
— The stroma comprises the supporting connective tissues, blood vessels, and immune cells.
Interactions between these components determine the growth and behaviors of the neoplasm.
Benign tumors are localized, organized, and tend to display slower growth.
— Because of these characteristics, benign tumors are typically amenable to surgical removal, which may be necessary when benign tumors grow large enough to impair functioning of the surrounding tissues.
Malignant tumors are invasive, disorganized, and often grow erratically; they are potentially metastatic, which means they can cross anatomical boundaries.
Benign tumors are often named by combing the cell type of origin with the suffix "-oma;" however, some important exception to this rule are the malignant tumors of lymphoma, mesothelioma, and melanoma.
Adenoma of the thyroid gland
Well differentiated, which means that the tumor cells resemble that of the normal thyroid gland.
It is functional, as we can see numerous colloid-filled follicles.
Relatively normal looking nuclei.
Pancreatic tissue with serous cystadenomas
Microcysts
The
pancreatic acini are relatively normal looking.
Serous cystadenomas are also often commonly found in the ovaries.
Squamous papillomas on the tongue
Numerous macroscopic fingerlike and warty projections.
When such projections extend into a lumen, they are called "polyps."
Sarcomas are malignant tumors that form in sold mesenchymal tissue, such as bone, fat, and muscle.
Leukemias and lymphomas are cancers of the white blood cell lines.
Carcinomas are tumors that form from epithelial cells, such as in the skin or the internal linings of the organs.
—
Squamous cell carcinomas: the tumor cells look like stratified squamous epithelium, and,
—
Adenocarcinomas: the tumor cells grow in a glandular pattern.
"Undifferentiated malignant tumors" are those of unknown tissue origins.
Adenocarcinoma in the colon
This is
anaplastic, that its, it is not well differentiated. The glandular tissue that has proliferated is not like that of the normal colon mucosa.
Even if this wasn't a malignant tumor, we can see how this would obstruct normal bowel functioning.
Oral squamous cell carcinoma
Pleiomorphic cells, which range from small to giant.
Large, hyperchromatic nuclei.
Several of the cells are in various stages of mitosis, reflective of their hyper-proliferative state.
Thyroid adenocarcinoma
The malignant tumor is anaplastic and disorganized.
It is nonfunctional, which we can see from the absence of colloid-filled follicles.
Metastatic brain tumor
It has irregular edges without a distinct enclosing capsule, which lends to its invasive nature.
Mixed tumors
The parenchymal cells of most tumors are uniform; however, denote that mixed tumors comprise multiple cell types.
For example, a mixed tumor of the salivary gland may comprise epithelial cells as well as other types not typically found in the gland.
Teratomas
The cells of most neoplasms are derived from a single germ cell layer; however, denote that teratomas comprise cells and tissues from multiple germ layers.
For example, we can see multiple tissue types in an ovarian teratoma, even hair and tooth-like structures.
