56. Structure and shape of tumors - macroscopic and microscopic characteristics. Role of immunohistochemistry for the diagnosis of tumors.

Introduction

This topic covers how a tumour is built (parenchyma and stroma), the shapes and growth patterns it takes macroscopically and microscopically, and how immunohistochemistry and tumour markers are used to diagnose it.

Structure of tumours

Tumours consist of two components:

• Parenchyma - the functional tumour cells.
• Stroma - connective tissue, blood vessels, nerves and extracellular matrix.

Depending on the ratio between the two components there are:

• Cirrhotic (scirrhous) tumours - contain a well-defined stroma.
• Medullary tumours - contain predominantly parenchyma.

Growth types of tumours

1. Unicentric - one proliferative centre.
2. Multicentric - several proliferative foci.
3. Exophytic - growing outwards, towards a cavity or surface (papillomas, polyps, mushroom-like (fungating) and cystic tumours).
4. Endophytic - growing inwards, into the underlying tissues (spherical/nodular and ulcerous tumours).

In relation to the surrounding tissue:

• Expansive growth - the tumour compresses the surrounding tissue.
• Infiltrative (invasive) growth - the tumour invades and destroys the surrounding tissue.
• Apposition - normal cells turn into cancer cells.