Cowden syndrome (PTEN hamartoma tumour syndrome)
PHTS — the umbrella term in current usage; Bannayan-Riley-Ruvalcaba syndrome, PTEN-related Proteus-like syndrome and Lhermitte-Duclos disease are part of the PHTS spectrum; "multiple hamartoma syndrome"
Cowden syndrome is a PTEN hamartoma tumour syndrome (PHTS) — an autosomal dominant cancer predisposition caused by germline mutations of the PTEN tumour suppressor gene on chromosome 10q23.31. The cardinal mucocutaneous features — multiple trichilemmomas, oral papillomatosis ("cobblestoning"), acral keratoses and palmoplantar pits — develop in adolescence and adulthood and are pathognomonic. The dermatologist or plastic surgeon is often the first to recognise the syndrome through these distinctive skin findings; prompt referral matters because affected individuals carry markedly elevated lifetime risks of breast carcinoma (lifetime risk up to ~85%; modern prospective cohort estimates vary widely between ~67% and ~85% — comparable to high-penetrance breast cancer syndromes such as BRCA1 and BRCA2, rather than clearly exceeding them), epithelial thyroid carcinoma (~25–35%), endometrial carcinoma (~20–28%), renal cell carcinoma (~15–35%), colorectal cancer (~10–15%) and melanoma (~5–6%). Lifelong organ-specific surveillance reduces cancer mortality.
Genetics
- Germline loss-of-function mutations of PTEN on chromosome 10q23.31 — a phosphatase tumour suppressor regulating PI3K-AKT-mTOR signalling.
- Autosomal dominant; high (~80–90%) but incomplete penetrance.
- De novo mutations common.
- Other PTEN-related conditions (Bannayan-Riley-Ruvalcaba syndrome, PTEN-related Proteus syndrome) overlap clinically — collectively termed PTEN hamartoma tumour syndrome (PHTS).
Mucocutaneous features (the dermatologist's clues)
- Multiple trichilemmomas — small skin-coloured papules around the eyelids, nose and mouth in adolescence; pathognomonic when multiple.
- Oral papillomatosis ("cobblestoning") — multiple small white papules on the gingivae and dorsum of the tongue.
- Palmoplantar pits — small (1–2 mm) translucent or punctate pits on palms and soles.
- Acral keratoses — flat-topped hyperkeratotic papules on the dorsa of hands and feet.
- Sclerotic fibromas, lipomas, vascular malformations.
- Macrocephaly (head circumference >97th centile) — useful clinical marker present in >80%.
Associated cancers (lifetime risk; ranges from modern prospective cohorts)
- Breast carcinoma in women — up to ~85% lifetime; modern prospective cohort estimates ~67–85%. Ductal carcinoma is the dominant histology; bilateral disease in up to half. Risk is broadly comparable to high-penetrance breast cancer syndromes (BRCA1 ~72%, BRCA2 ~69%) rather than clearly exceeding them.
- Epithelial thyroid carcinoma — ~25–35%; follicular and papillary; younger age at onset than sporadic.
- Endometrial carcinoma — ~20–28%.
- Renal cell carcinoma — ~15–35% (estimates vary widely across cohorts); predominantly papillary.
- Colorectal cancer — ~10–15%; multiple GI hamartomatous polyps.
- Melanoma — ~5–6%.
- Other: meningioma, glioma, dysplastic gangliocytoma of cerebellum (Lhermitte-Duclos disease — pathognomonic).
Diagnosis
- Suspect in any patient with multiple trichilemmomas, oral cobblestoning, macrocephaly, or two or more PHTS-spectrum cancers.
- 2013 Cleveland Clinic PHTS scoring system to estimate pre-test probability of a PTEN mutation.
- Genetic counselling and germline PTEN testing in clinical genetics service.
- Cascade testing of first-degree relatives.
Surveillance (NCCN-aligned)
- Breast — annual MRI from age 30; annual mammography from age 40; consider risk-reducing mastectomy from age 30 (after counselling).
- Thyroid — annual ultrasound from age 7 (paediatric onset described); thyroidectomy considered for nodular disease.
- Endometrium — annual transvaginal ultrasound and patient education to flag postmenopausal bleeding; consider hysterectomy at completion of childbearing.
- Renal — biennial renal MRI or ultrasound from age 40.
- Colorectum — colonoscopy every 5 years from age 35 (younger if symptoms or polyps).
- Skin — annual full-skin examination; biopsy any new lesion.
- Brain — MRI if neurological symptoms (Lhermitte-Duclos).
Management of skin lesions
- Cosmetic / functional excision of trichilemmomas; electrosurgery, laser or curettage acceptable.
- Topical / oral retinoids may suppress trichilemmoma development.
- Surveillance for atypical pigmented lesions (melanoma).
- Referral for genetic counselling and cancer surveillance is the priority.
References
- Pilarski R et al. Cowden syndrome and the PTEN hamartoma tumor syndrome — systematic review and revised diagnostic criteria. J Natl Cancer Inst; 2013.
- NCCN Clinical Practice Guidelines in Oncology. Genetic / Familial High-Risk Assessment: Breast, Ovarian, Pancreatic, and Prostate. Version 2.2026.
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