Hairy Cell Leukemia : A Clinicopathological Study of 18 Cases

Introduction: Hairy cell leukemia (HCL) is an uncommon chronic B-cell lymphoproliferative disorder. It affects primarily elderly men and presents with splenomegaly, pancytopenia and monocytopenia. It has to be differentiated from various chronic lymphoproliferative disorders (CLPDs) because of different protocol of treatment and clinical course. Methods: This study included 18 cases of HCL out of 300casesof CLPDs diagnosed over a period of 4 years (2009-2012) at tertiary cancer centre. All 18 cases were evaluated for clinical history, signs and symptoms, laboratory data, all initial and follow up peripheral blood smear (PBS) examinations, bone marrow aspirate (BMA) with imprint smear, bone marrow biopsy, immunophenotyping data, treatment details and response to treatment from medical records. Results: This study included 18 cases, age group of 35-69 years, with a median age of 40years and male predominance. M:F ratio was 6:1. HCL was 6% out of allCLPDs. Patients were presented with common complaints of weakness, fever and abdominal pain. On clinical examination, commonest findings were pallor, splenomegaly, hepatomegaly and abdominal lump. On laboratory investigations, 17 cases had anemia, 4 cases had leucocytosis, 11 cases had leucopenia and 11 cases had pancytopenia. On bone marrow biopsy,findings were diffuse infiltration of the marrow by atypical lymphoid cells having abundant cytoplasm. For immunophenotyping all patients` blood samples were CD19 gated on lymphocytes. It showed co expression of CD103, CD11c and CD25. Thirteen patients were treated with cladribine based chemotherapy with excellent responses. Conclusion: HCL clinically presents with pancytopenia and splenomegaly in middle aged male but few patient can present with unusual clinical features like absence of a palpable spleen, generalized lymphadenopathy and leucocytosis.


Introduction
Hairy cell leukemia (HCL) is an uncommon but distinct form of chronic B-cell lymphoproliferative disorder comprising about 2% of lymphoid leukemias. It affects primarily elderly men and is characterized by triad of splenomegaly, pancytopenia and monocytopenia. [1] Most of patients with HCL present with involvement of bone marrow, spleen and few cases with peripheral blood. Hairy cell have characteristic appearance of small to medium in size, moderate nuclear: cytoplasmic ratio, round to oval nuclei and having abundant cytoplasm exhibiting thin circumferentially cytoplasmic projections.(figure 1) The differential diagnosis of HCL from other chronic B-cell lymphoproliferative disorders is clinically important because patients with HCL respond better and highly sensitive to cladribine (2-chlorodeoxyadenosine ) a purine analogues and pentostatine ( 2-deoxycoformycin) based chemotherapy, but do not respond well to conventional lymphoma chemotherapy. These drugs give long term complete remission even in a significant portion of HCL patients with relapsed disease. [2][3][4][5] The final diagnosis of HCL mainly based on morphologic findings of hairy cells on peripheral blood smear (PBS), bone marrow(BM) and Flow cytometric immunophenotyping (IPT) of malignant cells. HCL has a characteristic immunophenotypic profile and light scatter characteristics. The tumor cells express B cell-associated markers CD19, CD20, CD22 and CD79b with characteristically positive for CD103, CD25, CD11c and usually negative for CD10, CD5 and CD23 Coexpression of CD103, CD25 and CD11c is unique for HCL, It is an absolute criteria for diagnosis of HCL . However atypical IPT have been reported in morphologically classical HCL. [6] In this study we evaluate clinicopathological features, immunophenotypic profile and treatment details.
2009 to December 2012) at tertiary cancer centre. HCL cases were suspected morphologically and diagnosis was confirmed by immunophenotyping. Total 18 cases of HCL and 1 case of HCL Variant were retrieved from medical records. All 18 cases were evaluated for clinical history, signs and symptoms, laboratory data, all initial and follow up peripheral blood smear (PBS) examinations, bone marrow aspirate (BMA) with imprint smear, bone marrow biopsy, immunophenotyping data, treatment details and response to treatment from medical records.

Morphology:
The peripheral smear and bone marrow aspirate smears were stained with wright stain for morphological examination. Bone marrow biopsy or tissue biopsy were stained with Hematoxylin and Eosin (H & E) stain. (Figure 1

Results
Age and sex distribution: Age range was from 35 to 69 years, with median age 40 years. Fifteen out of eighteen patients were male (83%), M:F ratio was 6:1. Duration of symptoms were from 6 months to 2 years.
Treatment and follow up: There were 18 cases of HCL diagnosed. Out of which, 13 cases were treated at same cancer centre. Nine patients received one cycle of cladribine based chemotherapy and all of them achieved complete remission .One patient was treated by splenectomy with supportive care but relapsed after 5 months of initial treatment detected on BMA during follow up , later treated by further 8 cycles of CHOP (cyclophosphamide, Doxorubicin, Vincristine, Prednisolone) chemotherapy. Three patients were poor not affording cladribine based chemotherapy and treated with CHOP based chemotherapy. One out of these three patients relapsed at 7 months after initial treatment and expired due to complications of neutropenia and its infective complications. All patients received neutropenia care. Five Patients were not appeared for treatment. Detailed follow up of treated patients was available for period of two months to sixty months after initial treatment. All these patients were alive and disease free without any signs, symptoms, organomegaly and had complete blood count within normal range.

Discussion
Accurate diagnosis of HCL is critical because therapy with purine analogues cladribine associated with high complete response rate and long relapse-free survival in patients with HCL but is less effective in patients with other chronic B-cell leukemias or lymphomas. [2][3][4][5][6][7] The diagnosis of HCL is usually made by examining the morphologic features of the hairy cell on PBS and BMA in conjunction with the characteristic immunophenotyping by FCM analysis. HCL constitutes approximately 6% of all CLPDs presenting at this institute. [6] This figure is much higher than incidence     of 2% reported in western literature. [1] HCL patients are symptomatic and referred to higher tertiary cancer centers for early management by physicians. This could explain higher incidence in this study compared to Western. In this study of 18 cases, median age being 40 years (ranging from 35 to 69 years), which is quite younger; however, it is correlated with the findings of another Indian study by Chatterjee T et al. [8] The youngest patient in this study was 35 years old comparable to that reported by Chatterjee T et al. [8] was 32 years. As per WHO, male predominance was also seen in this study (M: F=6:1). All the patients presented with symptoms like easy fatigability, fever, bleeding manifestations and weakness, all of which were reported in standard references. [1,7,8,9,10,11] On physical examination, splenomegaly was present in 78% of cases, which was less than the other studies. [7][8][9] Hepatomegaly was seen in 22% cases similar to findings of Galani et al. [9] Though uncommon, lymphadenopathy was seen in 7/18(38%) cases, all patients had generalized lymphadenopathy which is higher than values reported by other studies. [7,9] Anemia was the most common hematologic abnormality (94%) similar to other study. [9] Four patients had leukocytosis. Cases of HCL with profound lymphocytosis have been reported only rarely in the literature. [12] These findings show most patients with classic HCL usually present with pancytopenia, but rare cases can present with leukocytosis. This possibility should be kept in mind to provide accurate diagnosis and proper treatment.
Accurate diagnosis of HCL is critical because therapy with purine analogues is associated with high complete response rates and long relapse-free survival in patients with HCL but is less effective in patients with other CLPDs. [9] HCL is a monoclonal B-cell neoplasm with coexpression of CD19, CD103, CD11c and CD25. In the present study, 11% of the patients analyzed were CD10 positive which is within range of 5% to 26% reported by various studies. [6,9,13] In the present study, CD23 positivity was seen in 11% of HCL compared to 19% of study by Galani KS et al. [9] One patient in the present study had a transformation to large cell non hodgkin's lymphoma.
The value of FCM analysis of peripheral blood for diagnosis of HCL appears to be under-recognized by many physicians, perhaps due to a lack of familiarity with the capabilities of this technique and a misperception that leukopenic patients have very few circulating hairy cells for detection. [9] FCM is ideally suited for the diagnosis and therapeutic monitoring of diseases like HCL with low numbers of malignant cells in peripheral blood.

Limitations:
The diagnosis of HCL cases was based on a specific fixed panel of antibodies. TRAP was not available at this centre. Some patients didn't appear for treatment.

Conclusions
Higher incidence of HCL (6% of all CLPDs) at this centre may be due to referral tertiary cancer center. HCL can occur at a younger age, which may be due to geographical variation. Unusual clinical presentations of patients include absence of palpable spleen, presence of lymphadenopathy and leukocytosis. Variable expression of CD10 and CD23 can also be seen in HCL which are commonly used for diagnosis of follicular lymphoma and chronic lymphocytic leukemia. For accurate diagnosis of response to cladribine based chemotherapy is noted in majority of the patients.