In this rare form of mammary tumour, the mucous tissue develops from the stroma of the gland, and it may involve one or more lobules, or the whole gland, which is then converted into a bulky tumour. Sometimes the mucous tissue grows into the milk-ducts, forming the Myxoma intrantnalicukm arberescetu of Virobow.

Section of an adenoma of mamma.

Fig. 467. - Section of an adenoma of mamma. Glandular structures of well-formed outline are shown in the midst of fibrous tissue, x 90.

Mammary adenoma. Gland tissue with partial dilatation of duct.

Fig. 468. - Mammary adenoma. Gland tissue with partial dilatation of duct.

The tissue may be pure mucous tissue, but it is subject to various modifications. It may be unduly cellular so as to approach to the sarcoma, or it may be mixed with fat or fibrous tissue. It also contains glandular tissue, which may be dilated into cysts.

This form is more malignant than the adeno-fibroma, being more liable to recur after removal.