A patient with white blood cell counts more than a million: A diagnostic and therapeutic challenge

Abstract

Prolymphocytic leukemias (PLLs) are rare mature lymphoid disorders of B- and T-cell subtypes with distinct features and an aggressive clinical course. PLL represents only 2% of all mature lymphocytic leukemias in adults. T-PLL represents 20% of all PLLs cases. T-cell prolymphocytic leukemia (T-PLL) is more rare and more rapidly progressive and aggressive than B-PLL; it is generally resistant to conventional chemotherapy, and historically the median survival has been about 7 months. Clinicians will often only see a case of T-PLL once every 5 to 10 years, which makes recognition of the disorder difficult. The prognosis is poor and there is no curative therapy. We report a 77-year-old male patient with de novo T-PLL presenting with WBC count of 1,115,000. We will discuss the clinical, morphologic, immunophenotypic and cytogenetic features of this rare entity.

A distinctive hematologic aspect of T-PLL is a rapidly rising white blood cell count with a doubling time of weeks to months. The key morphologic feature in the diagnosis of T-PLL is a population of more than 55% prolymphocytes in the peripheral blood. The diagnosis can be made on peripheral blood by flow cytometry where a monoclonal lymphocyte population will show positivity for T-cell markers. T-PLL is characterized by complex chromosomal abnormalities, which suggests that chromosomal aberrations might occur progressively during the course of the disease, thus explaining the aggressive nature of this condition. The main challenge as a clinician treating T-PLL is to deliver long-term disease-free survival. The most important predictor of outcome is response to alemtuzumab therapy (Campath).

Knowledge of the disrupted pathways and mechanisms underlying activation and proliferation in T-PLL has raised the possibility of developing future and promising treatment approach that targets these pathways and signals by the use of future molecule inhibitors. T-PLL is a rare disease and careful attention should be given to correctly diagnose this T-cell leukemia. Physicians should be aware of this unusual entity. With the advent of alemtuzumab, although much progress has been made in the treatment of this disease, autologous or allogeneic hematologic stem cell transplant (HSCT) still remains the only hope for cure.

Introduction

Prolymphocytic leukemias (PLLs), first described in the 1970s, are rare mature lymphoid disorders of B- and T-cell subtypes with distinct features and an aggressive clinical course¹. PLL represents only 2% of all mature lymphocytic leukemias in adults over the age of 30³. PLL is clearly defined into B-PLL and T-PLL with T-PLL representing approximately 20% of the cases³. T-PLL is more rare and more rapidly progressive and aggressive than B-PLL, it is generally resistant to conventional chemotherapy, and historically the median survival has been about 7 months³. It is a rare mature post-thymic T-cell neoplasm and accounts for up to one-third of mature T-cell malignancies with a leukemic presentation, but account for only a very small percentage of all lymphoid malignancies¹. Clinicians will often only see a case of T-PLL once every 5 to 10 years, which makes recognition of the disorder difficult¹. Despite the advances in the understanding of the biology of this disease, the prognosis still remains poor with a short survival and no curative therapy². We report a case of de novo T-PLL and discuss the clinical, morphologic, immunophenotypic and cytogenetic features of this rare entity.

Case History

A 77-year-old male with past medical history of sarcoidosis (diagnosed and treated in the 1970's), who was in his usual state of health which consists of self care and independence in all activities of daily living until two months ago. Reports a gradual and progressive fatigue associated with generalized malaise. Symptoms were accompanied by mild abdominal discomfort and intermittent episodes of headaches. He denied fever, chills, night sweats, nausea, vomiting or changes in bowel habits. Reports weight loss of 60 lbs. in one year due to loss of appetite. Refers past hospitalization in 2010 for symptomatic anemia requiring red blood cell transfusions. Denies recent travel or previous history of any viral or bacterial infection. Family history was non-contributory.

On physical examination, patient appeared acutely ill, alert and fully oriented. Vital signs were remarkable for respiratory rate at 20 per min and O2 peripheral saturation was 90% at room air. There was diffuse pitting edema more evident in lower extremities and trunk. Conjunctival pallor and dry oral mucosa were noted along with periorbital edema. No extra heart sounds, murmurs or gallops. Lung auscultation was remarkable for decreased bibasilar sounds. Abdominal auscultation revealed normoactive bowel sounds. Percussion was dull in left upper abdominal quadrant. Palpation was remarkable for splenomegaly. No supraclavicular, axillary or inguinal lymphadenopathy was found. There was no evidence of any gross neurological deficits. Laboratories showed a LDH level of 321 U/L. Complete blood count was remarkable for a WBC count of 1,115, 000/μL. Hepatitis profile was negative as well as HTLV1/2, herpes, cytomegalovirus, and HIV serology. Beta-2 microglobulin was elevated (5.6mg/dL).

Due to an excessively elevated WBC count patient was initially managed with two leukopheresis. Chest X ray was remarkable for bilateral pleural effusions. Abdominal sonogram disclosed an enlarged spleen. Head CT scan was negative. Chest CT scan was remarkable for bilateral pleural effusion more prominent at left side. Abdominal CT scan was remarkable for splenomegaly and edematous changes of the subcutaneous fat tissue. There was no evidence of lymphadenopathy by imaging studies.

Flow cytometry and hematopathology of peripheral blood was done along with molecular and cytogenetic studies. Hematopathology disclosed markedly increased atypical lymphocytes found to be predominantly small in size with round to oval nuclei, mature chromatin and many of them showing small nucleolus as well as small amount of cytoplasm. There was macrocytic anemia with no significant morphologic abnormality and mild thrombocytopenia with no overt abnormal platelets (Fig 1-4). Flow cytometry disclosed peripheral blood with atypical T-cell population (around 85%) with immunophenotype favoring T-PLL (Fig 5). Cytogenetic analysis was remarkable for abnormal male karyotype with trisomy 8, monosomy 20 and an unbalanced rearrangement resulting in additional chromosomal material on the short arm of chromosome 12 and a paracentric inversion of the long arm of chromosome 14 resulting in TCR alpha and delta rearrangement. Inversion 14q is the genetic hallmark of T-PLL. Complex karyotypes are usually associated with an unfavorable prognosis (Fig 6). Fluorescence in situ hybridization (FISH) showed abnormal results with positive chromosome 8 and T-cell receptor (TCR) rearrangement (Fig 7). PCR was positive for a clonal T-cell receptor beta and gamma gene rearrangement. A positive result is consistent with the presence of a clonal lymphoid population in the sample. Once the diagnosis of T-PLL was confirmed, Alemtuzumab was initiated. Alemtuzumab is the first-line treatment for this rare entity.

Figure 1. Peripheral blood smears.

Markedly increased atypical lymphocytes which are predominantly small in size with round to oval nuclei, mature chromatin and many of them showing small nucleolus. They have small amount cytoplasm. Prolymphocytes with evidence of an intense basophilic nongranular cytoplasm with cytoplasmic protrusions and blebs. Macrocytic anemia is noted with no significant morphologic abnormality. There is mild thrombocytopenia and no overt abnormal platelets. Few scattered smudge cells are present.

Figure 4. Peripheral blood smears.

Genoptix^®

Figure 5. Flow cytometry.

An atypical CD4+ T-cell population (approximately 85%) is identified with brighter than usual CD3 expression, but no overt loss of other surface antigen. Immunophenotype favoring T-cell prolymphocytic leukemia (T-PLL). Genoptix^®.

Figure 6. Cytogenetic.

Abnormal male karyotype with trisomy 8, monosomy 20 and an unbalanced rearrangement resulting in additional chromosomal material on the short arm of chromosome 12 and a paracentric inversion of the long arm of chromosome 14. Genoptix^®

Figure 7. Fluorescence in situ hybridization (FISH).

shows abnormal results with chromosome 8 and TCR rearrangement. Genoptix^®

Discussion

The World Health Organization (WHO) classification of hematopoietic and lymphoid tumors recognizes 5 types of mature T-cell tumors that commonly involve the peripheral blood and bone marrow at presentation (Table 2). Of these, the rare entity of T-PLL accounts for only a very small percentage⁴.

Table 2.

Differential diagnosis of mature T-cell leukemias by immunophenotype¹. (Adapted from Blood, 19 July 2012; Vol 120, Num 3).

Immunophenotype	T-PLL	T-LGL	SS	ATLL
CD2	+	+	+	+
CDS	+	+	+	±
CD7	+ (strong)	±	±	−
CD4	+ (in 60%)	− (rarely +)	+ (most)	+ (most)
CDS	+ (15%)	+	Rare	Rare
CD4/CD8 coexpression	+ (25%)	Rare	Rare	Rare
Other antigen expression		CD 57/CD16 (often)		CD25 in most cases

T-PLL indicates T-cell prolymphocytic leukemia; T-LGL. T-large granular lymphocytic leukemia; SS. Sezary syndrome; and ATLL, adult T-cell leukemia lymphoma.

T-PLL was first described in 1973³. It primarily affects older adults with an average age at presentation of 65 years with male predominance³. The majority of patients present with hepatosplenomegaly (splenomegaly is more common) as well as generalized lymphadenopathy. Other common findings include skin lesions (27%) and pleural serous effusions (14%)⁵. These findings correlate with our patient.

The peripheral blood commonly exhibits anemia and thrombocytopenia with a marked lymphocytosis and lymphocyte counts frequently more than 100,000⁵. A distinctive hematologic aspect is a rapidly rising white blood cell count with a doubling time of weeks to months⁴. The key morphologic feature in the diagnosis of T-PLL is a population of prolymphocytes in the peripheral blood (55% or more). The typical morphology consists of prolymphocytes of medium size with condensed nuclear chromatin, a single prominent nucleolus, and intensely basophilic nongranular cytoplasm with cytoplasmic protrusions or “blebs”. The nuclei can be round, oval, or irregular⁶.

Most of these cytological features are found in the peripheral smears of our patient. In addition, the diagnosis can be made on peripheral blood flow cytometry where a monoclonal lymphocyte population will show positivity for T-cell markers including CD 2, CD 3, CD 5, CD 7 and CD52. CD4 and CD 8 expressions are variable. More than two-thirds of cases express CD3 and TCR-β in the cell membrane, whereas the remainder is negative with either one or both markers². In the patients lacking the surface expression of CD3 and TCR-β, these T cell-specific molecules are consistently expressed in the cytoplasm and the TCR-β and/or γ chain genes are rearranged in all cases. T-prolymphocytes express strong positivity to CD7 unlike the other mature T-cell leukemias².

T-PLL is characterized by complex chromosomal abnormalities, which suggests that chromosomal aberrations might occur progressively during the course of the disease, thus explaining the aggressive nature of this condition. Recurrent changes mainly affect chromosomes 8,11,14, and X⁷. The most common characteristic chromosome abnormality, seen in 80% of cases, is inversion of chromosome 14. T-PLL includes deletions of 12p13 and 11q22 mutated gene. Abnormalities of chromosome 6 and 17 and deletion of the TP53 gene might also be found⁸.

Differential diagnosis for T-PLL includes T-cell large granular lymphocytic leukemia, adult T-cell leukemia/lymphoma, Sézary syndrome and peripheral T-cell lymphoma. To discriminate between T-PLL and these other T-cell malignancies, it is crucial to integrate all the clinical and laboratory information (peripheral blood morphology, histology, immunological and genetic markers). T-PLL can be distinguished from B-PLL based on immunohistochemistry studies and the presence of lymphadenopathy and skin involvement (Table 1-2) ^1,2.

Table 1.

Clinical and laboratory characteristics of T- and B-cell PLLs¹. (Adapted from Blood, 19 July 2012; Vol 120, Num 3).

Characteristic findings	T-PLL	B-PLL
Clinical features	Median age 61 y	Median age 69 y
	Male:female 2:1	Male:female, 1.6:1
	Splenomegaly, lymphadenopathy, skin rash, edema and paraperitoneal effusions	B-symptoms. splenomegaly, minimal lymphadenopathy, high WBC
	Very high WBC
Morphology	Basophilic prolymphocytes with cytoplasmic blebs	> 55% prolymphocytes (usually > 90%)
	Small cell (20%) and SS (5%) variants	Prolymphocyte is 2 times the size of CLL lymphocyte
Immunophenotype	CD2+, CD3+, CD5+,	SmIG strong, CD19+,
	CD7++	CD20+, CD22+,
	CD4/CD8 variable	CD79a−, CD23− CD5±
	CD1a−, TdT−, CD25±	FMC7+ (CLL score 0-1)
Cytogenetics	t(14;14); inversion 14; t(X;14); iso8q; complex	13q del, 11q del. 17p del.6qdel
		No t(11;14)
Oncogenes	TCL-1, MTCP-1.ATM	TP53, C-MYC
Differential diagnosis	B-PLL, T-LGL leukemia, ATLL, SS	CLL/PL,* T-PLL, MCL (leukemic phase). SMZL, HCL-V
Prognosis	Median survival 7 mo with conventional therapy; 20 mo with alemtuzumab; 48 mo with alemtuzumab + HSCT	Median survival 3 y

T-PLL indicates T-cell prolymphocytic leukemia; T-LGL, T large granular lymphocytic leukemia; SS, Sezary syndrome; ATLL, adult T cell leukemia lymphoma; B-PLL, B-cell prolymphocytic leukemia; CLL/PL, chronic lymphocytic leukemia with increased prolymphocytes (< 55%); HCL-V, hairy cell leukemia variant; MCL, mantle cell lymphoma; SMZL, splenic marginal zone lymphoma; WBC, white blood cell count; and HSCT, hematopoietic stem cell transplant.

^*CLL/PL < 55% prolymphocytes.

There is not enough information regarding prognostic factors in T-PLL. Review of the literature demonstrates that biologic parameters, such as immunophenotype, cytogenetics, and molecular genetics, do not influence survival or response to therapy¹. The most important predictor of outcome is response to alemtuzumab therapy. In this regard, patients with extramedullary disease (eg, liver, CNS, pleuroperitoneal effusions) have lower response rate to alemtuzumab. In a series reported in Blood of 86 patients treated with alemtuzumab, nonresponders had a median survival of only 4 months¹. In the series reported from The MD Anderson Cancer Center, 5-year survival from diagnosis was 21% and poorer outcome was associated with high WBC, short lymphocyte doubling time, older age, and high expression of TCL-1 protein measured by flow cytometry and immunohistochemistry⁹.

The first-line treatment for T-PLL is alemtuzumab. Intravenous alemtuzumab (Campath), an anti-CD52, used either alone or in combination with a purine analogue (such as pentostatin, fludarabine, and cladribine) is an effective and well tolerated treatment, with overall response rates ranging between 51% and 95%, and a median survival of 15 to 19 months in patients achieving a complete response, increasing to 48 months after consolidation with autologous or allogeneic stem cell transplantation (SCT) ^10,11. It is not advisable to use a debulking strategy using steroids or multiagent regimens, such as CHOP, because this is usually ineffective, delays the response of antibody therapy, and adds substantial toxicity¹.

The main challenge as a clinician treating T-PLL is to deliver long-term disease-free survival. Although some responses with alemtuzumab are prolonged (more than 5 years), long term follow-up on patients treated with alemtuzumab in T-PLL case series suggests that all patients do eventually relapse¹². Experience with both autologous and allogeneic HSCT, although limited, is encouraging (Fig 8)¹³.

Figure 8.

Treatment algorithm for T-PLL¹. (Adapted from Blood, 19 July 2012; Vol 120, Num 3).

Most patients with T-PLL will not survive and new therapies are urgently needed. Knowledge of the disrupted pathways and mechanisms underlying activation and proliferation in T-PLL has raised the possibility of developing promising molecule inhibitors as treatment alternatives. T-PLL is a rare disease and careful attention should be given in order to correctly diagnose this T-cell leukemia. Physicians should be aware of this unusual entity. Owing to its aggressive and rapid clinical course, delay in making the diagnosis may lead to a fatal outcome. With the advent of alemtuzumab, although much progress has been made in the treatment of this disease, autologous and allogeneic hematologic stem cell transplant (HSCT) still remains the only hope for cure.

Figure 2. Peripheral blood smears.

Markedly increased atypical lymphocytes which are predominantly small in size with round to oval nuclei, mature chromatin and many of them showing small nucleolus. They have small amount cytoplasm. Prolymphocytes with evidence of an intense basophilic nongranular cytoplasm with cytoplasmic protrusions and blebs. Macrocytic anemia is noted with no significant morphologic abnormality. There is mild thrombocytopenia and no overt abnormal platelets. Few scattered smudge cells are present.

Figure 3. Peripheral blood smears.

Markedly increased atypical lymphocytes which are predominantly small in size with round to oval nuclei, mature chromatin and many of them showing small nucleolus. They have small amount cytoplasm. Prolymphocytes with evidence of an intense basophilic nongranular cytoplasm with cytoplasmic protrusions and blebs. Macrocytic anemia is noted with no significant morphologic abnormality. There is mild thrombocytopenia and no overt abnormal platelets. Few scattered smudge cells are present.