Cavernous angioma of the liver is the commonest form of primary tumour. Its structure has already been described (see p. 229 and Fig. 86). It develops apparently by dilatation of the existing capillaries and atrophy of the intervening hepatic cells, so that the tumour replaces a certain portion of hepatic tissue. When seated immediately under the capsule the tumours are visible as red blotches, and on section they have a red colour and collapsed appearance. Usually it is only after the blood is washed out that the white trabeculae become visible. The tumours present great varieties of size and may be as large as the fist. They occasionally project outwards from the general surface of the liver, but are generally level with this surface.

A case has been described by Ziegler of multiple Fibroneuroma in the liver on the fibres of the sympathetic, there being similar tumours on the various nerves of the body except the olfactory and optic.

Cysts are not infrequent in the liver, and they may be multiple. It is curious that multiple cysts of the kidneys and liver frequently co-exist, both forms being probably of congenital origin. The cysts in some cases replace a considerable portion of the liver tissue. A group of bulky thin-walled cysts occupies a large part of the liver substance. There is rarely an extreme transformation of the whole liver or a great part of it, such as occurs in cystic transformation of the kidneys.

In Leukaemia the liver is very frequently the seat of new-formations. This may take the form of a general infiltration of the interstitial connective tissue, but it often occurs as individual small nodules, somewhat resembling miliary tubercles but without the presence of giant-cells or any tendency to caseation. The round cells which form the nodules have been observed to show evidences of karyomitosis. The capillaries are commonly filled with leucocytes and the liver as a whole is much enlarged. Similar conditions are observed sometimes in Hodgkin's disease.

Concerning Adenoma of the liver there is considerable variety in statement and opinion, mainly because, on the one hand, this form of tumour is rare, and, on the other, there are tumours concerning which it is difficult to say whether they should be called cancers or adenomas. The form designated Nodular hyperplasia is clearly an adenoma, and the name may with convenience be confined to this form, as the other so-called adenomas have more the habit of cancers. It occurs as solitary or multiple tumours which, while perfectly defined, have a similar structure to the proper hepatic tissue, the cells being usually larger and some having double nuclei. If single the tumour may reach the size of a cherry or larger; if multiple they are smaller. The larger ones are sometimes surrounded by a connective tissue capsule. These tumours are of no practical consequence and are met with accidentally. They are not uncommon in the liver of the dog.

Adenoma of the liver is not infrequently associated with Cirrhosis, but the nature of the connection is not apparent.

Primary Cancer

This form of tumour is infrequent compared with secondary cancer, but in itself is not very uncommon. It occurs sometimes as a massive tumour involving a large part of the liver, but in addition to this large tumour there are frequently numerous secondary ones in the liver substance (see Fig. 411). In some cases the growth seems to arise from the bile ducts at the porta of the liver, and to extend into the substance of the organ. In regard to structure several forms have been distinguished, of which the principal are these:

Cylinder-celled epithelioma is a rare form of tumour in the liver: it is sometimes described under the name of tubular adenoma. In its structure it closely resembles the similar tumours of the stomach and rectum, consisting of tubular gland-like processes with cylindrical epithelium. As is usual with this class of tumours the cells in many of the alveoli are variously shaped and the typical structure is only visible at the growing margins. There may be several tumours or one large one. The structure of the tumour suggests an origin from the hepatic ducts, but according to Rindfleisch the gland processes arise from the hepatic cells inside the lobules. This form of tumour is not usually malignant, but in a case recorded by Greenfield secondary extension to a lymphatic gland and to the lungs had occurred.

Fig. 411. - Primary cancer of liver with secondary nodules. The bulky tumour in the anterior part of the right lobe is the primary cancer. (From a painting by Dr. A. Macphail).

The primary cancer in the liver has more frequently the structure of Ordinary cancer, which sometimes has the dense characters of Scirrhus. It may involve a considerable portion of the liver, perhaps the whole left lobe, and by shrinking reduce it to small dimensions. In structure the tumour presents the ordinary characters. At the marginal parts it may be seen sending processes into the hepatic capillaries and into the branches of the portal and hepatic veins.

There are also cases of so-called Infiltrated or Diffuse cancer in which the whole liver is affected. The organ is enlarged and granular on the surface, resembling the appearances in cirrhosis. There is here also a great increase of connective tissue, but in its meshes there is cancerous and not liver tissue. This form is sometimes called Cirrhosis carcino-matosa. It is as if there had been a great transformation or replacement of the liver tissue by cancer.

Lastly there is the form in which the cancer originates in the larger ducts and extends along the capsule of Glisson. The radiating appearance of the new formation is visible in this form, and there is also obstrnction of the ducts with retention of the bile and icterus.