Differentials
Chronic lymphocytic leukaemia (CLL)
SIGNS / SYMPTOMS
Clinically, CLL and HCL might be indistinguishable.
INVESTIGATIONS
Typically, the immunophenotypic profile for the abnormal B cell in CLL is CD5+ and CD23+ (rarely expressed in HCL), and negative for CD103 (commonly expressed in HCL).[45][50]
CD11c is expressed commonly in B-cell chronic lymphocytic leukaemia (B-CLL) and HCL, but the intensity of expression is 30-fold greater in HCL than in B-CLL.[45]
Mantle cell lymphoma
SIGNS / SYMPTOMS
Clinically, mantle cell lymphoma and HCL are indistinguishable.
INVESTIGATIONS
Over-expression of cyclin D1 owing to t(11;14) chromosome translocation is a hallmark of mantle cell lymphoma. However, weak expression of cyclin D1 can also be detected in HCL.[41][51][52] Typically, the immunophenotypic profile of the abnormal B cell in mantle cell lymphoma is positive for CD5 (rarely expressed in HCL).
Pro-lymphocytic leukaemia
Splenic marginal zone lymphoma (SMZL)/splenic lymphoma with villous lymphocytes (SLVL)
SIGNS / SYMPTOMS
Clinically and morphologically, HCL and SMZL/SLVL might be indistinguishable.
INVESTIGATIONS
SMZL/SLVL cells do not display tartrate-resistant acid phosphatase (TRAP)-positivity and the bone marrow infiltrates are demarcated sharply. The immunophenotypic profile is negative for CD103, CD27, and CD25.[45][52] CD11c is expressed commonly in SMZL/SLVL and HCL, but the intensity of expression is 30-fold greater in HCL than SMZL/SLVL.[45]
Annexin A1 (ANXA1) is negative in SMZL/SLVL, whereas it is positive in HCL.
Aplastic anaemia
SIGNS / SYMPTOMS
Clinically, aplastic anaemia and HCL are indistinguishable.
INVESTIGATIONS
Practitioners should beware of erroneous diagnosis of aplastic anaemia owing to a dry-tap bone marrow aspirate with hypo-cellular bone marrow. Immunostaining for B-cell antigens is essential and can prompt specific immunophenotyping for HCL.[41]
Hairy cell leukaemia variant (HCL-V; also known as splenic B-cell lymphoma/leukaemia with prominent nucleoli [SBLPN])
SIGNS / SYMPTOMS
Clinically, HCL-V/SBLPN and HCL are indistinguishable.
INVESTIGATIONS
Absolute monocyte count is usually normal.
HCL-V/SBLPN typically presents with leukocytosis with an average WBC count of approximately 35×10⁹/L (35,000/microlitre).
Typical immunophenotype profile is negative for CD25, annexin A1 (ANXA1), and CD123; the abnormal B-cell is TRAP negative.
BRAF V600E mutation is absent.[7][25]
Patients with HCL-V/SBLPN typically do not respond as well to standard HCL treatment.
Use of this content is subject to our disclaimer