A middle-aged man presents with a markedly enlarged tonsil and recurrent infections with serum immunoglobulin deficiency. Chromosome analysis demonstrates a translocation between the immunuglobulin heavy chain locus on chromosome 14 and an unidentified gene on chromosome 8. Which of the following is the most likely cause of his phenotype?

**Core Concept**
The underlying principle being tested involves the **pathogenesis of lymphomas**, specifically those related to **chromosomal translocations** affecting **immunoglobulin genes**. This scenario suggests a **malignant transformation** of B cells, given the involvement of the immunoglobulin heavy chain locus.

**Why the Correct Answer is Right**
The description points towards a **Burkitt lymphoma**, characterized by a translocation between the **immunoglobulin heavy chain locus on chromosome 14** and the **c-MYC gene on chromosome 8**, leading to **uncontrolled B-cell proliferation**. This translocation, t(8;14), is a hallmark of Burkitt lymphoma, explaining the patient's symptoms, including the enlarged tonsil and immunoglobulin deficiency due to the malignant transformation of B cells.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it does not specify the correct chromosomal translocation associated with the described clinical presentation.
**Option B:** Incorrect as it might relate to a different condition or translocation not characteristic of Burkitt lymphoma.
**Option C:** Incorrect because, although it might involve immunoglobulin genes, it does not accurately describe the specific translocation associated with Burkitt lymphoma.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that **Burkitt lymphoma** is associated with the **t(8;14) translocation**, which leads to the overexpression of the **c-MYC** oncogene, resulting in aggressive B-cell lymphoma. Recognizing this translocation is crucial for diagnosing and managing the disease.

**Correct Answer:** D. t(8;14) translocation

✓ Correct Answer: C. The translocation has activated a tumor-promoting gene on chromosome 8