The development and further growth of benign tumors (adenomas) that arise from these glands seem to be connected to the presence of sex hormones (the growth is stimulated by male hormones and suppressed by female). These tumors are regularly found together with certain testicular tumors (Leydig cell tumor).
Perianal adenomas only appear in bitches when their uterus and ovaries have been removed, although it is possible in exceptional cases by excessive production of testosterone by the adrenal glands.
Perianal adenomas grow slowly. They can become very extensive locally, but metastases do not occur.
These tumors appear in intact as well as in neutered males and females. It is however possible that hormones played a role in the transformation of this gland into a tumor. These tumors have a tendency to grow faster than the benign form, be less loose and firmer.
Perianal adenocarcinomas metastasize seldom (in about 15% of cases). The most frequent places metastases occur are the local lymph nodes, seldom the lungs, liver, kidneys and bone.
The benign form (adenoma) occurs relatively frequently (more than 50% of tumors around the anus), at an average age of 10 years, whilst the malignant form (adenocarcinoma) appears less frequently (between 3-21% of tumors around the anus) at an average age of 11 years.
The benign form occurs more in the Beagle, Bulldog, Cocker Spaniel and Samoyeed, whereas the malignant form mainly affects males of large races.
- Benign form: slowly growing (during months or years) tissue mass(es) which aren’t painful and usually aren’t associated with anomalies. They can also occur on the foreskin, ball sac or tail.
These tissue masses can ulcerate and infect, but are rarely really attached to the underlying structures. Usually, they are well delineated (average of 0.5 to 3 cm in diameter) and raised.
- Malignant form: this form resembles the benign one, but grows faster, is firmer, ulcerates, attaches to underlying tissues, relapses when the margins were very limited during surgery and is generally larger than the benign form. For large tissue masses the chances are higher this leads to obstruction and difficulties defecating, pain or irritation around the anus. Although rarely the case, it’s possible that the lymph nodes which contain metastases swell up so much, they’ll cause pressure on the intestines and severely complicate the stool passage.