A 48 year old woman was admitted with a history of weakness for two months. On examination, cervical lymph nodes were found enlarged and spleen was palpable 2 cm below the costal margin. Her hemoglobin was 10.5 g/dl, platelet count 237 x 109/L and total leukocyte count 40 x 109/L, which included 80% mature lymphoid cells with coarse clumped chromatin. Bone marrow revealed a nodular lymphoid infiltrate. The peripheral blood lymphoid cells were positive for CD 19, CD 5,CD 20 and Cd 23 and were negative for CD 79 B and FMC – 7.What is the most likely diagnosis ?

**Core Concept**
The patient's presentation with lymphadenopathy, splenomegaly, anemia, leukocytosis with lymphocytosis, and specific immunophenotypic markers suggests a lymphoproliferative disorder. The clinical and laboratory findings point towards a specific subtype of chronic lymphocytic leukemia (CLL), characterized by the expression of certain surface antigens.

**Why the Correct Answer is Right**
The patient's lymphoid cells express CD19, CD5, CD20, and CD23, which are characteristic markers of CLL. The absence of CD79B and FMC-7 further supports this diagnosis. CD5 is often expressed in CLL, which helps to distinguish it from other types of lymphoid neoplasms. The presence of CD20 and CD23 is also typical of CLL. The nodular lymphoid infiltrate in the bone marrow and the clinical presentation are consistent with CLL.

**Why Each Wrong Option is Incorrect**
* **Option B:** This option is incorrect because CLL is typically characterized by a gradual increase in lymphocyte count, whereas this option suggests an acute lymphoblastic leukemia (ALL) presentation, which is less likely given the patient's age and immunophenotypic markers.
* **Option C:** This option is incorrect because mantle cell lymphoma (MCL) is characterized by the expression of CD5, CD20, and CD23, but it also typically expresses CD79B and FMC-7, which are absent in this patient.
* **Option D:** This option is incorrect because follicular lymphoma (FL) is characterized by the expression of CD20 and FMC-7, but it does not typically express CD5 or CD23.

**Clinical Pearl / High-Yield Fact**
CLL is a chronic lymphoproliferative disorder that often presents with anemia, thrombocytopenia, and lymphocytosis. The expression of CD5 and CD23, along with the absence of CD79B and FMC-7, can help distinguish CLL from other types of lymphoid neoplasms.

**Correct Answer: C. Chronic Lymphocytic Leukemia (CLL)**

✓ Correct Answer: B. Chronic lymphocytic leukemia