Myd88 L265p mutation is seen in:
**Core Concept**
The Myd88 L265P mutation is a gain-of-function mutation in the MyD88 gene, which encodes a key adaptor protein in the Toll-like receptor (TLR) signaling pathway. This mutation leads to constitutive activation of the NF-κB pathway, resulting in abnormal immune cell activation and proliferation.
**Why the Correct Answer is Right**
The Myd88 L265P mutation is specifically associated with Waldenström macroglobulinemia (WM), a rare subtype of non-Hodgkin lymphoma. The mutation leads to the production of IgM monoclonal protein, which can cause hyperviscosity syndrome, a clinical feature of WM. The constitutive activation of the NF-κB pathway due to the Myd88 L265P mutation promotes the survival and proliferation of malignant lymphocytes.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the Myd88 L265P mutation is not typically associated with chronic lymphocytic leukemia (CLL). CLL is characterized by the accumulation of CD19+ CD5+ B cells, but the Myd88 L265P mutation is more specifically linked to WM.
**Option B:** This option is incorrect because the Myd88 L265P mutation is not typically associated with diffuse large B-cell lymphoma (DLBCL). While DLBCL is a common type of non-Hodgkin lymphoma, the Myd88 L265P mutation is more specifically linked to WM.
**Option C:** This option is incorrect because the Myd88 L265P mutation is not typically associated with follicular lymphoma (FL). FL is a type of non-Hodgkin lymphoma characterized by the accumulation of CD19+ CD10+ B cells, but the Myd88 L265P mutation is more specifically linked to WM.
**Clinical Pearl / High-Yield Fact**
The Myd88 L265P mutation is a key diagnostic marker for Waldenström macroglobulinemia, and its detection can guide targeted therapy with Bruton's tyrosine kinase (BTK) inhibitors.
**Correct Answer: C. Follicular lymphoma is not the answer as Myd88 L265P is associated with Waldenström macroglobulinemia.