As there are many glands of different structure, so are there various forms of adenoma. The several forms will be more particularly described under their respective organs, and it will only be necessary here to enumerate them. We have the mammary (see Fig. 92), the prostatic, the thyroid, the renal, and the hepatic adenomas. Besides these, the so-called mucous polypi, although often formed of hyper-trophied mucous membrane, frequently contain glandular tissue which is apparently, in some cases, new-formed. Again, in ovarian tumours there is frequently a new-formation of gland-tissue out of which cysts develop, so that the tumour is called an adenocystoma.

Mammary adenoma.

Fig. 92. - Mammary adenoma. Gland spaces are shown in a cellular fibrous stroma, x 64.

The term adenoma is not commonly used for tumours composed of lymphatic-gland tissue, although the expression lymph-adenoma is not infrequently employed. As the structure of lymphatic glands differs so markedly from that of the epithelial glands it is perhaps better to reserve the term adenoma for the latter, and to use that of lymphoma for the former.

A rather unfortunate custom of calling lymphatic tissue "adenoid tissue," without specifying that it is lymphatic, has become somewhat prevalent. It would conduce to clearness if the term lymphoid tissue were used instead.