Cowden syndrome can affect several parts of the body, and its features vary from person to person. A combination of certain signs may lead a clinician to consider PTEN hamartoma tumor syndrome (PHTS), but none of these signs alone proves that someone has it.
A larger-than-average head size, called macrocephaly, is a common feature. It may be noticed in childhood, sometimes alongside developmental delay, learning differences, or autism. A clinician considers head size in relation to age and other features; head size alone does not establish a diagnosis.

Many people develop skin or mouth growths. These may include small, often skin-colored bumps on the face; smooth or wart-like bumps in the mouth; or rough areas on the hands and feet. Some of these growths are hamartomas, which are noncancerous overgrowths of tissue normally found in that area. They may become more apparent over time. Their appearance can resemble other common skin conditions, so assessment by a clinician familiar with PHTS can be helpful.

Thyroid changes are another possible feature. These include thyroid nodules, goiter (an enlarged thyroid), or other benign thyroid growths. Thyroid nodules are common in the general population too, so their presence does not automatically indicate Cowden syndrome. A clinician will consider the full pattern of signs and family history.

Some people have polyps in the gastrointestinal tract. Polyps are growths on the inner lining of the digestive system. They may be found during an endoscopy or colonoscopy and may be of different types. Their number, type, and symptoms can vary. Abdominal symptoms or a polyp finding should be discussed with a healthcare professional, who can decide whether further assessment is needed.
Features can appear at different ages. Skin and mouth signs often become more noticeable by adulthood, while a large head size or developmental differences may draw attention earlier in childhood. A person may have some features but not others, and relatives with the same PTEN variant can have different experiences.

Doctors assess the whole picture: physical findings, personal medical history, family history of related cancers or features, and genetic test results. If the pattern raises concern, referral to a clinical geneticist or genetic counselor can help determine whether testing is appropriate. A diagnosis should not be made from a list of signs alone.