CLL, hairy cell leukemia

A) CLL / SLL (Chronic Lymphocytic Leukemia / Small Lymphocytic Lymphoma)

Overview

• Both are non-Hodgkin B-cell lymphomas — the same disease differing only in location:
  • CLL: cancer cells in blood and BM (leukemic)
  • SLL: cancer cells in lymph nodes and lymphoid tissue (lymphomatous)
• Indolent (slow-growing) neoplasm; peak incidence at 60 years

Pathogenesis

• BCL2 overexpression → inhibits apoptosis → slow tumor growth
• Suppresses normal B-cell function → hypogammaglobulinemia (↓ Ig production)
• In 15% of patients: autoimmunity → autoantibodies against own RBCs or platelets
• Displaces normal marrow elements → anemia, neutropenia, thrombocytopenia

Morphology

• Predominant cells: small resting lymphocytes with dark-staining round nuclei and scant cytoplasm
• Foci of larger, mitotically active cells → called proliferation centers
• Diffuse pattern — follicular structure of lymph node is not preserved
• Neoplastic lymphocytes are fragile → disrupted during smear prep → characteristic smudge cells
• BM, spleen, and liver also involved

Laboratory findings

Immunophenotype: CD19, CD20, CD23 + surface Ig — and CD5 (normally a T-cell marker)

Genotype:

• Trisomy 12 → good prognosis
• del(13q) → good prognosis
• del(11q) → bad prognosis
• del(17p) → bad prognosis
• Mutated IgH → good; unmutated IgH → bad

Clinical features

• Asymptomatic for a long time
• Leukemic blood picture: 15,000–150,000/µL
• Generalized lymphadenopathy and hepatosplenomegaly
• Less common: autoimmune hemolytic anemia, thrombocytopenia
• Richter transformation in 5–10% → sudden conversion to high-grade lymphoma
• Prognosis: diverse (good → watch & wait; bad → intensive chemo)

---

B) Hairy Cell Leukemia

Definition

• Rare, slow-growing peripheral B-cell tumor — considered a subtype of CLL
• Named for the distinctive hair-like cytoplasmic projections on neoplastic B-cells

Key features

• Occurs mostly in older males
• Hairy cells accumulate in BM and spleen → pancytopenia, splenomegaly, susceptibility to severe infections
• Symptoms: fatigue, weakness, fever, weight loss
• Very good prognosis — highly sensitive to chemotherapy

💡 High-yield: CLL = indolent NHL; CD19+/CD20+/CD23+ + CD5+ (T-cell marker on B-cell); smudge cells; BCL2 overexpression; Richter transformation (5–10%). Hairy cell = older males, pancytopenia, splenomegaly, very chemo-sensitive.