Adnexal tumour

Cutaneous adnexal tumours are numerous types of benign and malignant tumours that arise from:

• Hair follicles
• Sebaceous glands
• Eccrine and apocrine sweat glands

Adnexal tumours may be sporadic but are sometimes due to syndromes, such as:

• Birt-Hogg-Dube
• Brooke-Spiegler syndrome
• Cowden disease
• Muir-Torre syndrome (Lynch syndrome).

They are usually diagnosed by biopsy findings, rather than clinically. Their histological features are combined with special immunohistochemistry stains for a pathological diagnosis.

Benign eccrine and apocrine tumours include:

• Syringoma
• Poroma
• Cylindroma and spiradenoma
• Cutaneous mixed tumor
• Syringofibroadenoma
• Syringocystadenoma papilliferum
• Hidradenoma papilliferum
• Hidradenoma
• Tubular/papillary adenoma, including papillary cystadenoma.

Malignant eccrine and apocrine tumours include:

• Porocarcinoma
• Adenoid cystic carcinoma
• Mucinous carcinoma
• Microcystic adnexal carcinoma
• Digital papillary adenocarcinoma
• Extramammary Paget disease.

Benign follicular tumours include: 

• Trichoblastoma and trichoepithelioma
• Trichoadenoma
• Trichofolliculoma
• Trichilemmoma
• Trichodiscoma and fibrofolliculoma
• Tumour of the follicular infundibulum
• Panfolliculoma
• Pilomatricoma
• Proliferating trichilemmal tumour.

Malignant follicular tumours include: 

• Trichoblastic carcinoma
• Trichilemmal carcinoma
• Pilomatrix (matrical) carcinoma.

Sebaceous tumours include:

• Sebaceous hyperplasia
• Sebaceous adenoma and sebaceoma
• Sebaceous carcinoma.