Gorlin basal cell nevus syndrome or nevoid basal cell carcinoma syndrome (NBCCS) is an autosomal-dominant disease most commonly characterized by frontal bossing, broad nasal root, and hypertelorism. Patients present with basal cell carcinoma (BCC), which tend to be more aggressive in those with NBCCS.
NBCCS is caused by mutations in the human homolog of the patched (PTCH) gene on chromosome 9q. These mutations are highly penetrant (97%) but variably expressed. NBCCS occurs most often in whites (75%-80% in whites vs 30%-38% in blacks) and causes characteristic palmoplantar pits that start singly in childhood or adolescence and continue throughout life.
Skin lesions range from small pinpoint size to larger nodular BCC. However, nodular, ulcerating, and sclerosing BCC also occurs. Tumors on the eyelids, axillae, and neck are generally pedunculated and often symmetric. Palmoplantar lesions occur in 50% of patients as small pits that are pinpoint to several millimeters in size and 1 mm deep.
Other symptoms may also occur in other organ systems. These include skeletal malformations and manifestations in the eyes, soft tissue, central nervous system, and endocrine organs. A review of systems may show congenital anomalies including undescended testes and hydrocephalus and mandibular jaw odontogenic keratocysts, which may be numerous and unilateral or bilateral. There may be defective dentition, bifid or splayed ribs, pectus excavatum, short fourth metacarpal, scoliosis, or kyphosis. Eye lesions include strabismus, hypertelorism, dystopia canthorum, cataracts, glaucoma, and coloboma with blindness. There may be agenesis of the corpus callosum, calcification of the falx cerebri, and medulloblastoma. Intellectual disability is rare. Fibrosarcoma of the jaw, ovarian fibromas, teratomas, and cystadenomas have been reported.
Sun exposure and radiation therapy increase the risk for BCC. Radiation therapy should be avoided in those with NBCCS.
The following studies are indicated for those suspected of having NBCCS:
- Skull radiograph or computed tomography, which can show calcified falx cerebri, complete or partial bridging of the sella turcica, or broadened nasal root.
- Panoramic films, which may help identify odontogenic keratocysts and magnetic resonance imaging, which shows the internal composition of the cysts.
- Chest x-ray to document rib abnormalities.
- Hand and foot x-rays to reveal flame-shaped lucencies (lytic bone lesions), present on 30% of hand films and 17% of foot films.
- Skin biopsy of BCC that displays nodules and/or strands of atypical basaloid cells showing nuclear palisading, cellular apoptosis, and scattered mitotic activity in the dermis. Artifactual cleft formation may be seen between the tumor lobules and the surrounding stroma and may be mucinous. Solar elastosis is normally present in the dermis.