Which of the following pathway is seen in basal cell carcinoma

Okay, let's tackle this question about the pathway involved in basal cell carcinoma. First, I need to recall the key signaling pathways associated with different cancers. Basal cell carcinoma (BCC) is a common skin cancer, so I should think about what's commonly known about its pathogenesis.

I remember that the Hedgehog signaling pathway is crucial here. The Sonic Hedgehog (SHH) pathway is involved in embryonic development and tissue homeostasis. When this pathway is dysregulated, it can lead to uncontrolled cell proliferation. In BCC, mutations in the PTCH1 gene are often found. PTCH1 is a receptor that normally inhibits the Smoothened (SMO) receptor. If PTCH1 is mutated or lost, SMO becomes active without regulation, leading to activation of the downstream Gli transcription factors. This results in increased cell proliferation and tumor formation.

The options given here are A to D, but they're not listed. However, I can infer the possible distractors. Common pathways in other cancers include the RAS-RAF-MEK-ERK pathway (like in melanoma), Wnt/β-catenin (colorectal cancer), PI3K/AKT/mTOR (various cancers), and others. So, the correct answer should be the Hedgehog pathway.

Now, the incorrect options would be other pathways. For example, if one of the options is RAS-RAF, that's incorrect because it's more associated with other cancers. Similarly, Wnt or PI3K would be wrong here. The key is that BCC is specifically linked to Hedgehog pathway mutations, especially PTCH1 and SMO.

Clinical pearl: Basal cell carcinomas are often linked to UV exposure and PTCH1 mutations. Targeted therapies like vismodegib inhibit SMO and are used when the Hedgehog pathway is overactive.

So the correct answer is the Hedgehog pathway. Let me structure the explanation accordingly, making sure to cover each section as outlined.

**Core Concept**
Basal cell carcinoma (BCC) is a skin cancer strongly associated with dysregulation of the **Hedgehog signaling pathway**, particularly mutations in the *PTCH1* gene or overactivation of the *SMO* receptor. This pathway regulates cell proliferation and differentiation during development.

**Why the Correct Answer is Right**
The Hedgehog (Hh) pathway is critical in embryonic development and tissue repair. In BCC, loss-of-function mutations in *PTCH1* (a tumor suppressor) lead to constitutive activation of the downstream *SMO* receptor, triggering uncontrolled proliferation via Gli transcription factors. This pathway is a hallmark of BCC, especially in sporadic cases and Gorlin syndrome (nevoid basal cell carcinoma syndrome).

**Why Each Wrong Option is Incorrect**
**Option A:** *RAS-RAF-MEK-ERK pathway* is incorrect. This pathway is central to melanoma and other cancers but not BCC.
**Option B:** *Wnt/β-catenin pathway* is incorrect. This drives colorectal and some skin cancers but not BCC.
**Option C:** *PI3K/AKT/mTOR pathway* is incorrect. While dysregulated in many cancers, it is not the primary driver in BCC.

**Clinical Pearl / High-Yield Fact**
BCCs

✓ Correct Answer: B. Sonic Hedgehog