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Definition
Primary cutaneous marginal zone B-cell
lymphoma (MZL) is an indolent lymphoma
composed of small B cells including
marginal zone (centrocyte-like) or
monocytoid cells, lymphoplasmacytoid
cells and plasma cells. It is considered
part of the broad group of extranodal
marginal zone B-cell lymphomas commonly
involving mucosal sites (mucosa
associated lymphoid tissue, MALT).
Primary cutaneous immunocytoma, primary
cutaneous plasmacytoma and
cutaneous follicular lymphoid hyperplasia
with monotypic plasma cells are considered
variants of MZL.
Synonyms
EORTC (1997): Primary cutaneous
immunocytoma / marginal zone B-cell
lymphoma
Epidemiology
MZL most commonly affects adults aged
over 40 years. There is no clear gender
preponderance.
Etiology
In Europe, Borrelia burgdorferi DNA has
been identified in some cases of MZL
suggesting that it may play an etiological
role. However, no association of
Borrelia with CBCL has been found in the
United States and Asia.
Localization
MZL is predominantly localized on the
upper extremitites, and less often head
and trunk.
Clinical features
In most cases, cutaneous MZL presents
with red to violaceous plaques or nodules
with an erythematous border.
Ulceration and visceral dissemination are
uncommon. MZL with secondary spread
to the skin is often multifocal.
Histopathology
The infiltrate is characterized by residual
reactive (x40) lymphoid follicles (x100 - x200) surrounded by
pale staining cuffs of tumour cells.
Reactive germinal centres with distinct
mantle zones are commonly found in
early lesions but may become colonized
by tumour cells as the disease progresses (x400).
The interfollicular infiltrate is composed
of small to medium-sized, centrocyte-
like or monocytoid cells with slightly
irregular nuclei, moderately dispersed
chromatin, inconspicuous nucleoli and a
rim of pale cytoplasm.
Variable numbers of lymphoplasmacytoid
cells and plasma cells are typically
present at the periphery of the infiltrates
or in the subepidermal area. Intranuclear
PAS positive pseudoinclusions (Dutcher
bodies), are commonly found, particularly
in plasma cell rich forms of MZL.
Diffuse infiltrates almost completely consisting
of monocytoid cells, lymphoepithelial
lesions (absence, EMA)with infiltration of sweat
glands and the presence of very immature
plasma cells should raise suspicion
of secondary cutaneous involvement.
Immunoprofile
The neoplastic cells express CD19+,
CD20+, CD22+, CD79a+, but are negative
for CD5-, CD10-, bcl-6, CD23-. CD43
may be positive. In contrast to FL,
the tumour cells are bcl-2+, but negative
for bcl-6 and CD10. Reactive germinal centres are bcl-6+ and bcl-2-.
Anti-CD21 staining often reveals regular
and irregular networks of follicular dendritic
cells (FDC) in reactive follicles, but
not associated with tumour cells. The
lymphoplasmacytoid cells and the plasma
cells show monotypic expression of
immunoglobulin light chains. There are
numerous admixed reactive T-cells.
Precursor lesion
Cutaneous lymphoid hyperplasia due to
Borrelia infection may mimic MZL and
has been postulated to represent a precursor
lesion in some circumstances.
Histogenesis
Post germinal centre B-lymphocyte with
plasmacytic differentiation and gene
expression pattern.
Somatic genetics
IgH genes are clonally rearranged. The
most common translocation in gastric
MZL, the t(11;18) involving the API2/MLT
genes, has not been demonstrated in primary
cutaneous MZL.
However, the t(14;18)(q32;q21) involving
IGH and MALT1 was reported in approximately
one third of cases in a small
series. Fas gene mutations are present in
a minority of cases, similar to MZL of
other extranodal sites. Abnormalities of
BCL10 are absent.
Prognosis
MZL shows a protracted clinical course
with a tendency for recurrences.
However, the prognosis is favourable
with 5-year-survival rates between 90
and 100%. Transformation into diffuse
large B cell lymphoma occurs infrequently.
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