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A rare non-malignant adnexal sweat gland neoplasm characterized by asymptomatic, skin-colored to pink papules or plaques with a highly variable appearance, most commonly in the head and neck area.
ORPHA:840Classification level: Disorder
- Fistulous vegetative verrucous hydradenoma
- Naevus syringocystadenomatosus papilliferus
- Syringadenoma papilliferum
- Prevalence: Unknown
- Inheritance: Not applicable
- Age of onset: Childhood, Neonatal, Infancy, Adolescent
- ICD-10: D23.9
- OMIM: -
- UMLS: C0406803
- MeSH: -
- GARD: 5100
- MedDRA: 10042926
The prevalence of SCAP is not known. About 300 cases have been reported to date. The condition has been reported in various ethnic groups.
Syringocystadenoma papilliferum usually develops during childhood or adolescence, but some patients report lesions from birth. SCAP presents as generally slow developing, non-specific, smooth skin-colored to pink papules, often solitary or hairless plaques (smooth or raised, usually less than 4 cm in diameter, and are skin-colored to brown). Three clinical types of the SCAP have been described: the plaque type, the linear type and the solitary nodular type. At puberty, nodular or verrucous transformation is often observed, and lesions may increase in size and become crusted. Rarely, linear and segmental variants are found. The most common sites are the scalp and forehead (75% of cases occurring in the head and neck area). Unusual sites include the eyelids, arms and axilla, chest, back, breast, abdomen, genitalia and inguinal regions, perineal area, and lower limbs. SCAP may develop de novo or be associated with nevus sebaceous in about a third of cases, or with basal cell carcinoma in 10% of cases. Other commonly associated lesions include sebaceous epithelioma, apocrine hidrocystoma, clear cell syringoma, trichoepithelioma, tubular apocrine adenoma, and eccrine spiradenoma. Transition to malignancy is possible. Syringocystadenocarcinoma papilliferum is the malignant counterpart to this lesion.
The etiology of SCAP has not been elucidated. It is not known whether SCAP derives from eccrine or apocrine glands. The role of pluripotent stem cells has also been suggested.
Diagnosis is based on the clinical presentation of non-distinctive lesions which can be misleading, and confirmation is obtained through biopsy and histological examination revealing cystic, papillary, and ductal invaginations into the dermis lined by double-layered outer cuboidal and luminal high columnar epithelium and connected to the epidermis. Dilated capillaries and a dense infiltrate of plasma cells are characteristic. Immunohistochemically, the tumor stains positively for carcinoembryonic antigen.
The differential diagnosis is broad, requiring histological confirmation of cases. Conditions to consider include viral warts, subcutaneous fungal infection, linear verrucous nevus, pyogenic granuloma, warty dyskeratoma, inverted follicular keratosis, as well as eccrine nevus, nevus comedonicus, cylindroma, and basaloid follicular hamartoma.
Management and treatment
Treatment involves complete surgical excision. Carbon dioxide laser treatment can be useful for lesions in anatomic areas not favorable for surgery.
The condition is mostly benign but extensive lesions may have an impact on quality of life and transformation to malignancy cannot be ruled out.