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Basal cell carcinoma: Etiology, Morphology-NotesMed

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What is Basal cell carcinoma?

Basal cell carcinoma is a locally invasive, slow-growing tumor mass of the skin of middle-aged people that rarely metastasizes. It occurs exclusively on the hairy area of the skin, the face is the most common location being about 90%.
Site: Hair skin exposed to sun, usually above a line joining lobe of the ear to the corner of the mouth.


  • Chronic sun exposure in those living in New Zealand and Austria
  • Incidence increases with immunosuppression
  • Mechanisms of inheritance defects in DNA repairs in xeroderma pigmentosa
  • Nevoid basal cell carcinoma syndrome
    • Autosomal dominant condition in which multiple times basal cell carcinoma appears at a younger age mostly under 20 years.
    • Inheritance defects of one allele PTCH gene on chromosome number 9 while another allele undergoes mutation in early life by sun exposure are (Hudson’s two-hit hypothesis).


Morphology Basal cell carcinoma 


The most common form is a nodulo-ulcerative BCC in initially slow-growing small nodules which undergo central ulceration (lesion) with rolled, pearly margins.
At an advanced lesion, the tumor becomes enlarged in size by destroying the tissues locally by burrowing like a rodent and hence the name ‘rodent ulcer’.
However, less frequently non-ulcerated nodular patterns with pigmented basal cell carcinoma (BCC) and fibrosing variants are also encountered.


In BCC, the most common characteristic feature is the proliferation of basaloid cells which resembles the normal basal layer of the epidermis.
Tumor cells resemble the normal basal cell layer of the epidermis and are referred to by some as basaloma (germinative) cells.
Tumor cells are deeply basophilic epithelial cells and have an oval, large, or elongated nucleus with a narrow rim present in the cytoplasm.
This carcinoma have two patterns of tumor including;

  • Multifocal growth: it is originating from the epidermis and extending multifocal superficially along the surface.
  • Nodular growth:
    • They grow downward into the dermis as cords and islands of basophilic cells with a hyperchromatic nucleus in a mucinous matrix.
    • The peripheral cells of the tumor cell island tend to be arranged readily as peripheral palisading.
    • The stroma shrinks away from the tumor nests-retraction separation artifact.

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