Basal Cell Carcinoma ((Rodent Ulcer):
● It is locally aggressive cutaneous tumor associated with mutations that activate the Hedgehog pathway signaling.
■ It is most common invasive skin cancer in human being.
■ Most common site (90%) is face (usually above a line from the lobe of the ear to the corner of the mouth).
■ They are slow growing and rarely metastasize.
■ Risk factors include chronic sun exposure, fair complexion, immunosuppression, and defects in DNA repair (xeroderma pigmentosum).
■ Nevoid basal cell carcinoma syndrome (NBCCS or Gorlin syndrome) :
> It is a rare autosomal dominant disorder.
> Due to mutation in PTCH gene on chromosome 9q22 which encodes the receptor for the sonic hedgehog gene (SHH) gene product.
> Characterized by multiple basal cell carcinomas occurring before 20 years of age.
> Patients also develop medulloblastomas, ovarian fibromas, odontogenic keratocysts, and pits of the palms and soles.
■ Tumors typically present as pearly papules, often with prominent telangiectatic vessels; some are melanin-pigmented.
■ Advanced lesions ulcerate and can show extensive local invasion, hence the term rodent ulcer.
■ Microscopically, most characteristic feature is the proliferation of basaloid cells (resembling basal layer of epidermis)
■ The cells at the periphery of the tumor cell islands tend to be arranged radially with their long axes in parallel alignment (palisading).