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 2.7 X 1091L 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, CD5, CD20 and CD23 and were negative for CD 79 B and FMC-7.The histopathological examination of the lymph node in this patient will most likely exhibit effacement of lymph node arachitecture by –

**Question:** The peripheral blood lymphoid cells in the described patient were positive for CD19, CD5, CD20, and CD23, and negative for CD79B and FMC-7. The histopathological examination of the lymph node in this patient will most likely exhibit effacement of lymph node architecture by -

A. Hyperplasia
B. Lymphoma infiltration
C. Inflammatory cell infiltrate
D. Hemophagocytic histiocytes

**Core Concept:** The described patient exhibits clinical and laboratory findings consistent with B cell lymphoproliferative disorder. B cell lymphoproliferative disorders involve the uncontrolled proliferation of B cells, leading to infiltration of lymph nodes, spleen, and other organs.

**Why the Correct Answer is Right:**

In this case, the patient's clinical presentation, laboratory findings, and immunophenotype (expression of CD19, CD5, CD20, and CD23 on lymphoid cells while being negative for CD79B and FMC-7) point towards a B cell lymphoproliferative disorder. The histopathological examination of the lymph node will most likely exhibit effacement of lymph node architecture due to infiltration by B cells with similar immunophenotype.

**Why Each Wrong Option is Incorrect:**

A. Hyperplasia (Option A) typically refers to an increase in the size of an organ due to increased cell mass, and does not describe the infiltration of lymph nodes by abnormal lymphocytes.

B. While lymphoma is a type of B cell lymphoproliferative disorder, the question specifically mentions the effacement of lymph node architecture due to infiltration, and not just an increase in size. Thus, lymphoma (Option B) is not the correct answer.

C. Inflammatory cell infiltrate (Option C) does not describe the infiltration of lymph nodes by abnormal lymphocytes.

D. Hemophagocytic histiocytes (Option D) are macrophages that engulf red blood cells, and do not describe the infiltration of lymph nodes by abnormal lymphocytes.

**Clinical Pearls:**

1. The immunophenotype of the lymphoid cells (CD19, CD5, CD20, and CD23) helps differentiate between different types of B cell lymphoproliferative disorders.
2. The presence of a normal B cell receptor gene rearrangement by PCR (polymerase chain reaction) is essential in confirming the diagnosis of B cell lymphoproliferative disorders.
3. The clinical presentation, immunophenotype, and histopathology are crucial in diagnosing B cell lymphoproliferative disorders and distinguishing them from other similar disorders like Castleman's disease or reactive lymphadenopathy.

✓ Correct Answer: D. A diffuse proliferation of medium to large lymphoid cells with high mitotic rate