Which of the following differentiates invasive carcinoma from carcinoma insitu
Correct Answer: Basement membrane invasion
Description: Ref Robbins 9/e p271 Basement membrane invasion is the most impoant differentiating features between invasive carcinoma from carcinoma insitu A benign neoplasm remains localized at its site of origin. It does not have the capacity to infiltrate, invade, or metas- tasize to distant sites, as do malignant neoplasms. For example, as adenomas slowly expand, most develop an enclosing fibrous capsule that separates them from the host tissue. This capsule probably is derived from the stroma of the host tissue as the parenchymal cells atrophy under the pressure of the expanding tumor. The stroma of the tumor itself also may contribute to the capsule (Figs. 5-7 and 5-8). Of note, however, not all benign neoplasms are encapsulated. For example, the leiomyoma of the uterus is discretely demarcated from the surrounding smooth muscle by a zone of compressed and attenuated normal myometrium, but there is no well-developed capsule. Nonetheless, a well-defined cleavage plane exists around these lesions. A few benign tumors are neither encapsulated nor discretely defined; such lack of demarcation is paicularly likely to be seen in some benign vascular neoplasms of the dermis. These exceptions are pointed out only to emphasize that although encapsulation is the rule in benign tumors, the lack of a capsule does not mean that a tumor is malignant. Cancers grow by progressive infiltration, invasion, destruc- tion, and penetration of the surrounding tissue (Figs. 5-9 and 5-10). They do not develop well-defined capsules. There are, however, occasional instances in which a slowly growing malignant tumor deceptively appears to be encased by the stroma of the surrounding host tissue, but microscopic examination usually reveals tiny crablike feet penetrating the margin and infiltrating adjacent structures. The infiltrative mode of growth makes it necessary to remove a wide margin of surrounding normal tissue when surgical excision of a malignant tumor is attempted. Surgical pathologists carefully examine the margins of resected tumors to ensure that they are devoid of cancer cells (clean margins). Next to the development of metastases, local invasiveness is the most reliable feature that distinguishes malignant from benign tumors.
Category:
Anatomy
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