Follicular lymphoma Flashcards
What are the features of follicular lymphoma?
Nodular growth pattern (becomes more diffuse as disease progresse)
Even distribution of follicles (as opposed to cortical in reactive)
Neoplastic follicles have fuzzy edges
Small lymphoid cells with cleaved nuclei
Larger cells with rim of cytoplasm, vesicular nuclei, multiple nucleoli
Follicular dendritic cells also seen
Abscence of tingible body macrophages
What is the immunoprofile of follicular lymphoma?
Pan-B antigens: CD19, CD20, CD22, CD79a
Surface Ig (usu IgM) with light chain restriction
Interfollicular CD10 and Bcl-6 (usu expressed in germinal centres in benign LNs)
Bcl-2 in most cases (usu seen in benign memory cells and T cells).
CD5 usu negative
CD21 highlights dendritic follicular cells
What is the problem in trying to use Bcl-2 to distinguish between FCL and other low grade lymphomas?
They are often Bcl-2 +ve, and so Bcl-6 and CD10 are more useful
What is the hallmark genetic alternation of follicular lymphomas?
Which genes are juxtaposed?
t(14;18)(q32;q21)
IGH with BCL2, causing overexpression of BCL2
What does BCL-2 gene do?
It is an anti-apoptotic molecule, normally switched off in germinal centre B cells
Which follicular lymphomas typically do not show the BCL-2 rearrangement?
Paediatric FCLs
Primary cutaneous follicle centre lymphoma
Grade 3b FCLs
How often does BCL-6 translocation occur?
What is its relation to BCL-2 translocation?
In 10% of cases
Usually mutually exclusive to BCL-2 translocation
Associated with Grade 3b histology and lack of CD10 and BCL-2 expression
NB: we are talking about BCL-6 translocation, not expression. BCL6 expression occurs in most cases!
How are follicular lymphomas graded?
Grade 1 = 0-5 centroblasts per hpf
Grade 2 = 6-15 centroblasts per hpf
Grade 3 = >15 centroblasts per hpf
3a = admixed with centrocytes, infrequent mitoses
3b = pure centroblasts, more mitoses
What is the prognosis of FCL?
Grades 1 and 2 - more usually generalised disease, indolent course
Grade 3 - usually localised disease, aggressive course
What is the course of extranodal spread of follicular lymphoma in:
Spleen
Liver
Skin
Bone marrow
Spleen: white pulp
Liver: periportal
Skin: dermal infiltrate with no relation to vessels or adnexae
Bone marrow: paratrabecular
What morphological variations can occur in FCL?
Bands of fibrosis - esp in G3 tumours, retroperitoneal tumours
Monocytoid B cell or marginal zone differentiation
Proteinaceous material deposit in middle of nodules
Large eosinophilic globules (prob Igs) in cytoplasm causing signet ring effect
Plasmacytic differentiation in follicle centre
Cerebriform/multilobated nuclei
Granulomas
Preserved reactive germinal centres in early disease
