Extranodal Marginal Zone Lymphoma (MALT) Flashcards
1
Q
What is the definition of Extranodal
Marginal Zone Lymphoma (MALT)?
A
- morphologically heterogeneous small B cells including marginal zone (centrocyte-like) cells
- monocytoid cells
- small lymphocytes
- immunoblasts/scattered centroblasts
- IMP:
- plasmacytic differentiation can occur and can be quite extensive
2
Q
In lymph nodes, where are the neoplastic
lymphocytes located ?
A
- in the marginal zones of reactive B cell follicles
- extending into the interfollicular regions of the lymph node
- extending into the follicles (Follicular colonization)
3
Q
Where are the neoplastic lymphocytes located
in epithelial tissues?
A
- typically infiltrate into the epithelium
- Lymphoepithelial lesions are common
- Note:
- can recapitulate Peyer’s patches, which are the normal counterpart of mucosal associated lymphoid tissue
- There are site specific differences of MALT lymphomas despite many have similar morphology.
4
Q
What are the key epidemiological features
of MALT lymphoma ?
A
- MALT accounts for 8% of all B cell lymphomas, but up to 50% of those found in the stomach.
- Most patients in 7th decade of life, M = F except for areas such as the thyroid and salivary gland.
5
Q
What is the name and geographical locations of
the special subtype of MALT lymphoma ?
A
- Alpha Heavy Chain Disease
- also known as Immunoproliferative Small Intestinal Disease
- Found in Middle East, Cape region of South Africa
- also seen in a variety of other tropical and subtropical locations
- Campylobacter infection has been suggested as a cause
6
Q
What is the clinical link/situation that
frequently is associated with MALT?
A
- chronic inflammatory disorders leading to chronic stimulation
- autoimmunity
- Sjogren’s and Hashimoto thyroiditis
- infection
- H. pylori is the classica example
- either specifically activates T cells or has direct oncogenic effects on the background B cells
- sometimes antibiotic therapy is helpful in leading to remission
- unknown/other
- autoimmunity
7
Q
What is the most common site for
MALT lymphomas ?
A
- Stomach is the most common site for MALT
- Other common sites include:
- eyes/ocular adnexa
- skin
- lungs
- salivary glands
- breast
- thyroid
8
Q
What are some of the clinical features
of MALT lymphoma ?
A
- many patients present with stage I or II disease
- but up to 40% can have involvement of multiple extranodal sites
- BUT some of the other lymph nodes may represent separate clones rather than disease spread
- Minority of patients have bone marrow involvement 2-20%
- IMP:
- involvement of other sites and the bone marrow is more common in non-gastric MALT
- IMP:
- serum paraprotein can be detected in 1/3 of patients
9
Q
What are the microscopic findings of
MALT lymphomas ?
A
- small to medium sized cells with irregular nuclear contours, moderately dispersed chromatin and inconspicuous nucleoli.
- can look like centrocytes but with more abundant cytoplasm
- or can look like small lymphocytes
- Plasmacytic differentiation is common!
- cutaneous (don’t diagnose as plasmacytoma)
- frequently in thyroid and rarely in gastric
- large cells are present but should be minority
- The background can have uninvolved germinal centers
- if follicular colonization occurs it can be mistaken for Follicular lymphoma
10
Q
What is the definition of lymphoepithelial lesions?
A
- aggregates of >3 marginal zone cells with distortion or destruction of the epithelium.
- often can see eosinophilic degeneration of the epithelium.
11
Q
What is the morphology of MALT
lymphoma within the lymph nodes ?
A
- invades the marginal zone with subsequent interfollicular expansion
- discrete aggregates of monocytoid-like B cells
- perifollicular and perisinusoidal distribution
- cytologic heterogeneity is often seen
- plasmacytoid cells
- follicular colonization is also present
12
Q
MALT lymphoma can have increased foci
of large cells, true or false?
A
- True
- They can have centroblast or immunoblast-like morphology
- BUT
- once you start having shee-like proliferations of large cells then the tumor has transformed and you call it a DLBCL with mention of the accompanying MALT lymphoma
- DO NOT use the term High-grade MALT lymphoma
13
Q
What is the immunophenotype frequently seen
with MALT lymphoma ?
A
- (+)
- CD20, CD79a, CD43(sometimes), CD11c(weak)
- Light chain restriction can be helpful in differentiating from hyperplasia
- (-)
- CD5, CD10, CD23
- Infrequent cases are CD5(+)
- Rare cases are CD10(+) and Bcl6(-)
- Expanded FDC meshworks are seen by CD21, CD23, and CD35
- Correspond to the colonized follicles
14
Q
What are two emerging antibodies that may be
helpful in diagnosing MALT lymphoma ?
A
- IRTA1
- possibly specific for Marginal zone lymphoma
- antibody is not widely available
- MNDA
- helps when there is a differential diagnosis between follicular lymphoma
- nuclear antigen
- up to 75% of Marginal zone positive
- <10% Follicular lymphomas positive
15
Q
What immunoglobulins are frequently expressed by
MALT lymphoma ?
A
- IgM heavy chains - usually
- less frequently will see IgA or IgG
- IMP exception: Cutaneous Marginal Zone Lymphoma
- Two subtypes
- More common class switched with IgG (many IgG4) or IgA expression with predominantly background T cells
- Less common subtype (up to 25%) has an IgM subset with predominantly B cells in the background
