Nodular Lymphocytic Predominant Hodgkin’s Lymphoma


Hodgkin lymphoma (HL) is of two types. Classical (cHL) and nodular lymphocyte predominant (NLPHL). NLPHL is rarer and runs a more indolent clinical course.

Epidemiology

NLPHL accounts for about 5% of all HL.

Age: The disease is characterised by two peaks. The first one in childhood and the second between the ages of 30-40.

Gender: NLPHL shows a male predominance. About three-fourth of the patients are males. Male preponderance is less marked in blacks.

Racial Differences: Black patients are younger, more often female and more often present with axillary involvement. Little is known of NLPHL in other races (Cancer 2015; 121:3472-80).

Familial Susceptibility: Family members of patients with NLPHL at increased risk NLPHL. The standardised incidence ratio in one study was reported to be 19 (J Clin Oncol 2013; 31;938-43).

Histology

The normal architecture of the node is effaced and replaced by large nodules. Occasionally there may be large nodules with diffuse areas. Sometimes uninvolved nodal tissue may be seen. This is usually located peripheral in a sub-capsular area.

Microscopically NLPHL shows the malignant cell, LP cell, in a background mainly made up of small lymphocytes and with a prominent follicular dendritic cell (FDC) network. The follicular dendritic cell meshwork is absent from the diffuse areas. Unlike most other malignancies (and like cHL and T cell/Histolytic rich large B cell lymphoma) the normal reactive cells form the bulk of the enlarged node.

The LP cell has a nucleus that shows complex lobulation. It resembles a exploded kernel of corn and hence the cell is also referred to as the popcorn cell. The nucleolus is smaller than that of the RS cell and lies peripherally and is basophilic. There is a thin rim of cytoplasm.

The infiltrate in a nodule mainly consists of small lymphocytes. Unlike cHL, Eosinophils and plasma cells are occasional or may be absent. Most of the small lymphocytes making up the nodule are CD20+, CD79+ small B lymphocytes. The LP cells is however immediately surrounded by CD20, CD3+ T helper cells that express PD-1 and CD57. Diffuse area have CD4+ T cells and areas between nodes have CD3+ parafollicular T cells.

Varient histological patterns are known, associated with adverse prognosis and should be reported (Am J Surg Pathol 2003;27:1346-56).

Immunophenotype helps in diagnosis and has given clues to the origin of LP cells. The LP cells show a B cell phenotype and express CD20, CD79, CD22, PAX-5 and CD45. They express BCL-6 indicating the germinal centre origin. They do not express BCL-2. They strongly express the B cell transcription factor OCT-2 and its cofactor BOB.1. This distinguishes then from the Reed-Sternberg (RS) cells of cHL. RS cells show a weak expression or do not express these factors. RS cells express CD15, CD30 and fascin that are not expressed by the LP cells. About a fifth of the patients express IgD. These patients tend to be male, present with cervical adenopathy and have a greater risk of having a variant histology.

The normal counterpart of the LP cell appears to be the germinal centre B cell at the cenrtoblastic stage of differentiation.

NLPHL as well as cHL are diseases characterised by malignant cells surrounded by an infiltrate of normal cells. Unlike other cancers, the normal cells form the bulk of the tumour mass in both the cases. The malignant cells affect and are affected by the normal cells surrounding them. LP cells, like normal germinal centre cells, appear to depend on normal immunoglobulin receptor signalling. RS cells depends on other signalling receptors e.g. CD30 and CD40. The growth of normal germinal centre cells depends on The FDC and follicular T cells. These cells also support the growth of LP cells. The LP cell do not produce cytokines at levels seen in the RS cell. B symptoms are less common NLPHL less common than cHL.

 

 

Clinical Presentation

The most common presentation of NLPHL is isolated lymphadenopathy, most often in the cervical, axillary or the inguinal region. The swelling is usually present for a long time and has been growing slowly. About 80% of the patients present with localised disease and less than 20% with stage III/IV (Ann Hematol. 2016; 95: 417–423). B symptoms are uncommon (about 5%). Extranodal disease is very uncommon.

NLPHL runs a more indolent course that cHL. It is characterised by a relapses and transformation to high grade lymphoma diffuse large B cell lymphoma (including T cell/ histiocyte rich large B cell lymphoma). Relapses usually respond to treatment.

Staging

NLPHL, like cHL is classified by the Ann Arbor staging system with Cotswolds modifications. The stages are summarised below. A more detailed staging can be found here.

  1. Stage I: Involvement of one nodal region, lymphoid structure or one extra-nodal site
  2. Stage II: More than one region involved but disease limited to one side of the diaphragm.
  3. Stage III: Disease on both sides of the diaphragm but limited to the lymphoid system.
  4. Stage IV: Disease disseminated to one or more extra nodal organs.

Patients with fever with hight sweats and significant (>10% in the preceding 6 months) are said to have B symptoms.

The staging workup should include clinical examination, haemogram, ESR and biochemistry. NLPHL is PET avid. PET-CT is better than CT for staging. It is of value in to exclude diseases dissemination in patients where observation or local treatments are being considered. The value is interim PET-CT is NLPHL is uncertain. The bone marrow is very uncommonly involved (about 1-2%). Only patients with advanced disease should be subjected to bone marrow examination.

 

Differential Diagnosis

  1. Lymphocyte Rich Classical Hodgkin lymphoma
  2. T cell/ Histiocyte Rich Large B Cell Lymphoma
  3. Progressively Trasnformed germinal centres
  4. Follicular Lymphoma
  5. Mantle cell Lymphoma

 

Treatment

Early disease (Stage I/IIA)

Patients who have undergone excision biopsy that has resulted in a complete removal of all disease may be observed. Despite a lower progression free survival the patients who are observed do not show an inferior overall survival. This indicates that delaying treatment (radiation, chemotherapy or both as may be appropriate) does not hamper it’s efficacy.

Advanced Disease (Stage IIB, III, IV)

These patients need chemotherapy with the anti-CD20 antibody, rituximab. Three approaches are possible

  1. Classical Hodgkin lymphoma like therapy with Rituximab with ABVD: R-ABVD (Rituximab, doxorubicin, bleomycin, vinblastine and dacarbazine) should be administered to patients needing chemotherapy.
  2. B cell non-Hodgkin Lymphoma like therapy: R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, prednisone) is the standard treatment for high grade B cell non-hodgkin lymphoma. R-CHOP has been shown to effective in disease control and reducing the risk of transformation. It may be preferred in patients at a high risk of transformation, though there is not comparative trial with R-ABVD. Males and those with variant histology are at a higher risk of transformation. Models for predicting transformation are available.
  3. Single agent Rituximab: Single agent rituximab is indicated in patients with co-morbidities. The risk of relapse remains high.

Treatment of Relapse

Relapses must be rebiopsied to confirm NLPHL and to exclude transformation to a high grade lymphoma. Localized relapses may be treated with radiation. Chemotherapy should be used for other patients. Patients who have a chemosensitive relapse may be considered for allogenic stem cell transplant (Am J Haematol 2017 Oct 3. doi: 10.1002/ajh.24927).

Treatment of Transformation

Patients who undergo transformation are treated with regimen for regimens for high grade B cell lymphoma. The limited data suggests that the outcome is no different from that of de novo large B cell lymphoma.

 

Prognosis

The prognosis of NLHPL is better than conventional HL partially because of a more favourable disease profile – early stage, no B symptoms, no Bulky disease. One study showed a 94% overall survival at 10years (Ann Hematol. 2016; 95: 417–423). The progression free survival was 75% indicating relapses are common but are curable. Progression to diffuse large B cell lymphoma is seen in 5-10% of the patients. Atypical histology increases the risk of relapse (Blood. 2013 Dec 19;122(26):4246-52).

 

 

Advertisements

The BCR-ABL1 Gene


CML Pathogenesis-600pxBCR-ABL1 is a fusion gene formed as a result of the t(9;22)(q34;q11) chromosomal translocation, the translocation that results in the formation of the Philadelphia chromosome. The Abelson murine leukaemia viral oncogene homolog 1 (ABL1) gene from 9q34 is translocated downstream to a region at 22q11 known as breakpoint cluster (BCR). The fusion gene encodes for a constitutionally active tyrosine kinase that has been shown to drive the expression chronic myeloid leukaemia phenotype. BCR-ABL1 gene has also been on implicated in the pathogens is of acute lymphoblastic leukaemia and in rare cases of acute myeloid leukaemia. The gene has been targeted with unparalleled success by the first tyrosine kinase inhibitor approved in clinical practice, imatinib.

 Molecular Biology of BCR-ABL

The ABL1 proto-oncogene is located on chromosome 9 at q34. Chromosome 22 has the BCR gene at 22q11. The ABL1 gene translocated downstream to the BCR gene as a result of the t(9;22)(q34;q11) translocation. ABL1-BCR translocation also occurs and may express but is of no clinical significance.

 

Molecular Biology of CML

The BCR-ABL1 fusion gene and it’s variants

The breakpoint of the ABL1 gene may be upstream exon 1a, between exon 1a and 1b or downstream exon 1b but it is almost always upstream exon 2. With rare exceptions all transcripts of BCR1-ABL1 gene have exon 2-11 of the ABL1 gene. The BCR breakpoints are variable and determine the size as well as the pathogenic properties of the BCR-ABL1 gene.. The breakpoint on the BCR gene are clustered in three regions known major cluster, minor cluster and micro cluster (Table 1). Depending on the location of breakpoint  on the BCR gene three types of protein are synthesized. The p210 transcript is associated with CML and some patients with Philadelphia positive acute lymphoblastic leukaemia. The shorter p190 transcript is associated with philedelphia positive acute lymphoblastic leukaemia and some patients of chronic myeloid leukaemia. The CML that carry this mutation show monocytosis and have a more aggressive course. The p230 is the largest and the rarest of the BCR-ABL1 transcripts. It is associated with a more indolent course and is found in patients with the rare chronic neutrophilic leukaemia. Atypical transcripts e1a3, e13a3 and e6a2 have been described.

Table 1: The BCR-ABL1 fusion genes

 Major Cluster  Minor Cluster  Micro-Cluster
 Synonym M-Cluster m-cluster µ-cluster
Location exons 12-16 Between alternative exon 2, e2’ and e2 between exons e19 and e20
Protein p210 p190 p230
Associated Leukaemia  CML, e14a2 shown to have thrombocytosis in some studies., Ph+ ALL  Ph + ALL; CML that tends to have monocytosis and an agressive course  Chronic Neutrophilic Leukaemia, Small reports describing patients with a course resembling classical CML

Mutagenicity of BCR-ABL1

ABL1 is a nuclear kinase whose activity is tightly regulated by the cell. BCR-ABL1 translocation results loss of regulation and the kinase is  cosntitutively active. Sustitution of ABL1 at the N termnal by segments of the BCR gene result in the synthesis of a protein that has the capacity to dimerise. Dimerisation transphosphorylates and then aurtophsophorylates the the kinase fully activating it. The precise mechanism how BCR-ABL1 leads to chronic myeloid leukaemia is not known but activation of  phosphatidylinositol kinase, RAS/Mitogen activated protein kinase and JAK/STAT pathway has been demonstrated in BCR-ABL1 positive cells. These pathways are involved in cellular growth and differentiation. The BCR-ABL1 kinase also phosphorylates proteins involved in adhesion and migration and this may have a role in premature release of myeloid cells in circulation. CML cells have a two to sixfold increase in reactive oxygen species and have impaired DNA repair. Reactive oxygen species can induce DNA double strand breaks. The results is additional mutations and these are believed to be responsible for blast crisis and acclerates phase.

Tyrosine kinase inhibitors targeting the BCR-ABL1 protein induce a remission in most patients of CML. About half the patients who have achieved sustained complete molecular response relapse on discontinuation of the tyrosine kinase inhibitors. This suggests that the stemat least some CML stem cells are not BCR-ABL1 dependent for growth. Experimental observations support this hypothesis.

Targeting the BCR-ABL1 Gene

The BCR-ABL1 gene was the first gene to be targeted by a tyrosine kinase inhibitor, imatinib. Imatinib was followed by dasatinib, nilotinib, Busotinib and Panotinob. Imatanib, Dasatinib and Nilotinib are approved to first line use. Imatinib has resulted in a 85% 8 year survival. Dasatinib and nolitinib are active in imatinib resistant CML and are now approved for first line use. Drug resistance results from mutations in BCR-ABL1 kinase. The T315I mutation or the gatekeeper mutations impaires access of TKIs to the BCR-ABL1 kinase making most drugs inactive. Panotinib can inhibit the T315I mutation.

 

Further Reading

Barnes DJ Melo JV. Molecular Basis of Chronic Myleoid Leukaemia. In Chronic Myeloproliferative Disorders: Cytogenetic and Molecular Anomalies. Bain Barbra J (Ed) 2003.

Primary Cutaneous DLBCL – Leg Type


The first description of a primary cutaneous diffuse large B cell lymphoma was by Willemze et al in 1987 who described a group of elderly women with cutaneous large cell lymphomas with tumours in the legs and a worse prognosis ( Am J Pathol. Feb 1987; 126(2): 325–333).

Primary cutaneous diffuse large B cell lymphoma, leg type is a type of high grade cutaneous B cell lymphomas that was included as a separate entity in the WHO 2008 lymphoma classification. It forms about 20% of all cutaneous B cell lymphomas and about 4% of all cutaneous lymphomas. It is more common in women and the median age of occurrence is the 7th decade.

Pathology

Primary cutaneous large B cell lymphoma is characterized by a monotonous, diffuse, non-epidermotrophic infiltrate that is CD 20 and CD79a positive. and almost always express BCL2, IRF4/MUM1 and FOX-P1. The latter three markers are not expressed in in the primary cutaneous follicular centre cell lymphoma  another type of primary cutaneous B cell lymphoma. BCL6 is usually expressed but CD10 is not. 

Clinical Features

DLBCL-LT is a disease of elderly women (M:F:12-4, median age 70 years). Though called leg type, only 85-90% of the primary cutaneous DLBCL, leg type occur in the legs. The remaining occur at other sites. Patients present with a rapidly growing red or reddish blue nodule on one or both the legs. Patients may have ulceration and may be confused with venous ulcer. Unlike other cutaneous lymphomas primary cutaneous DLBCL, leg type disseminates to non-cutaneous sites.

Treatment

Radiotherapy

As DLBCL-LT has a tendency to disseminate to extra-cutaneous sites than other cutaneous lymphomas radiation is less effective in this disease. . A complete response rate of 88%  with a high (58%) relapse rate has been reported. relapses are in the in field and extra-cutaneous.

Chemotherapy

R-CHOP is the standard first line therapy. Dose reduction may be needed in elderly. Single agent rituximab is also an option but is associated with a high rate of recurrences. Linelidomide has been used in patients with relapse.

Leukaemia – The Peripheral Smear


Differentiating Acute and Chronic Leukaemia

Leucocytosis with anaemia is a feature of acute and chronic leukaemia. It is possible to differentiate acute and chronic leukaemia by looking at the peripheral smear. Patients with acute leukaemia often have thrombocytopenia. Patients with chronic lymphocytic leukaemia may have normal or low platelet counts. Patients with chronic myeloid leukaemia have normal or high platelet counts.

Haemoglobin Platelets Peripheral Smear
Acute Leukaemia Low Low Immature forms other than blasts not seen
Chronic Lymphocytic Leukaemia Low or Normal Low or Normal Normal looking lymphocytes
Chronic Myeloid Leukaemia Low or Normal Normal or High Immature leucocytes, all phases of leucocyte maturation seen

The phases of maturation of myeloid cells (from the least to the msot mature) are blasts, promyelocytes, myelocytes, metamyelocytes, band form and mature granulocyte (see Myeloid Precursors Morphlogy). The peripheral smear from patients with acute leukaemia shows blasts (or promyelocytes) and mature neutrophils. Very few cells, if any, with maturity between the two stages that occupy two ends of the spectrum are seen. Patients with with chronic myeloid leukaemia have cells with all stages of maturity between blasts and mature granulocytes. The peripheral smear in patients with acute leukaemia shows mature lymphocytes.

The explanation for the different peripheral smear findings in acute leukaemia and chronic myeloid leukaemia is in the pathogenesis of the two diseases. Chronic myeloid is a myeloprolferative disease. It is a clonal disease. The stem cells of patients with chronic myeloid leukaemia carry the BCR-ABL mutation. This mutation results in clonal expansion. All blood cells in a patient arise from one clone. The release of cells from the bone marrow of patients with CML is not limited to mature granulocytes. Some cells leave the marrow and result in leucocytosis.

The marrow of a patient of acute leukaemia has two clone one malignant one normal. The malignant clone can not differentiate beyond the stage of a blast (or promyelocyte). It slowly effaces the normal clone. The mature granulocytes seen in the peripheral smear arise from the normal clone and the blasts from the malignant clone. The normal clone releases cells only when they mature to the stage of band cell or beyond. The malignant clone can not mature beyond the stage of a blast. The stages between blasts and band forms/mature granulocytes are not seen in peripheral smear of acute leukaemia.

Monocyte and Neutrophils


Monocyte and Two Neutrophils

Monocyte and Two Neutrophils

The photomicrograph above shows a monocyte (left) and two neutrophils(right) and highlights the differences between the two.

The monocyte is mononuclear cell 12-20µm in diameter (about 1.5-2.5 times an erythrocyte). The nucleus is kidney shaped or U shaped and has a fine chromatin. The cytoplasm is blue-grey cytoplasm with fine azurophilic granules and may show vacuolation. These features are seen in the monocyte in the photomicrograph above.

Neutrophil, a contrasting cell,  is smaller (12-15µm or 1.5-2 times the erythrocyte), has a nucleus with 3-5 lobes with a clumped chromatin. The cytoplasm has pink granules.

 

 

Multiple Myeloma


Multiple Myeloma 01 600px

Normal plasma cells are 15-20 μm in diameter, have an eccentric nucleus and a pale blue cytoplasm. there is a perinuclear halo which corresponds to the Golgi apparatus. The cytoplasm may show vacuoles.

The nucleus has clumped chromatin. The cartwheel or clock-faced pattern is less evident on smears than on histological sections. It is normal for cccasional cells to have have two or more nucleus.

The figure above shows plasm cells from a patients with multiple myeloma that are farly normal. Plasma cells morphology in patients with multiple myeloma ranges from normal to moderate to severe dysplasia.

Sickle Cells


Sickle Cell - 100X - IMG_0542

Sickle Cells 40X

Sickle Cell 100X - IMG_0540

Sickle Cells – 100X

Sickle Cell 100X - IMG_0538

Sickle Cells – 100X


The three photomicrographs above show sickle cells from a patients with sickle cell anemia. Sickle cell anaemia occurs because an A→T substitution in codon 6 of the β globin chain of haemoglobin. The single nucleotide polymorphism results in valine substituting for glutamic acid resulting in the formation of haemoglobin S (HbS). HbS crystallizes in hypoxic conditions resulting in sickling of erythrocytes.

Related articles
Sickle Haemoglobin and Variants