**Core Concept**
Rhabdomyosarcoma is a type of soft tissue sarcoma that originates from skeletal muscle cells. The prognosis of this malignancy largely depends on the site and extent of the tumor, as well as the age of the patient. Specifically, the site of the tumor is a critical determinant of the overall outcome.

**Why the Correct Answer is Right**
Tumors located in the extremities (e.g., arms or legs) tend to have a poorer prognosis compared to those found in other sites. This is because extremity tumors often present at a more advanced stage, with larger tumor size and higher metastatic potential. Additionally, the extremities have a rich network of lymphatic vessels, which can facilitate the spread of cancer cells. In contrast, tumors in other sites like the orbit, paratesticular region, or urinary bladder tend to present at an earlier stage and have a better response to treatment.

**Why Each Wrong Option is Incorrect**
**Option A:** Orbit tumors tend to have a relatively better prognosis due to their localized nature and the effectiveness of surgical resection and adjuvant therapy.
**Option C:** Paratesticular rhabdomyosarcoma, particularly in children, has a favorable prognosis due to its high sensitivity to chemotherapy and radiation therapy.
**Option D:** Urinary bladder tumors, although rare, tend to have a relatively good prognosis compared to extremity tumors, mainly due to their early detection and effective treatment options.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the prognosis of rhabdomyosarcoma is also influenced by the age of the patient, with infants and children generally having a better outcome than adults.

**Correct Answer:**
✓ Correct Answer: B. Extremity