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benign tumors

Tuesday 24 March 2009

In general, benign tumors are designated by attaching the suffix -oma to the cell of origin.

Tumors of mesenchymal cells generally follow this rule. For example, a benign tumor arising from fibroblastic cells is called a fibroma, a cartilaginous tumor is a chondroma, and a tumor of osteoblasts is an osteoma.

In contrast, nomenclature of benign epithelial tumors is more complex. They are variously classified, some based on their cells of origin, others on microscopic architecture, and still others on their macroscopic patterns.

Adenoma is the term applied to a benign epithelial neoplasm that forms glandular patterns as well as to tumors derived from glands but not necessarily reproducing glandular patterns.

On this basis, a benign epithelial neoplasm that arises from renal tubular cells growing in the form of numerous tightly clustered small glands would be termed an adenoma, as would a heterogeneous mass of adrenal cortical cells growing in no distinctive pattern.

Benign epithelial neoplasms producing microscopically or macroscopically visible finger-like or warty projections from epithelial surfaces are referred to as papillomas.

Those that form large cystic masses, as in the ovary, are referred to as cystadenomas. Some tumors produce papillary patterns that protrude into cystic spaces and are called papillary cystadenomas.

When a neoplasm, benign or malignant, produces a macroscopically visible projection above a mucosal surface and projects, for example, into the gastric or colonic lumen, it is termed a polyp.

The term polyp is preferably restricted to benign tumors. Malignant polyps are better designated polypoid cancers.