Primary Cutaneous Follicle Centre Lymphoma Flashcards
1
Q
What is the definition of
PCFCL ?
A
- tumor of neoplastic follicle centre cells
- includes centrocytes and variable # of centroblasts
- growth pattern can be follicular, follicular and diffuse or diffuse
- generally presents on the head or trunk
IMP:
- lymphomas with a diffuse pattern and predominantly centroblasts or immunoblasts irrespective of site are:
- Primary Cutaneous Large B cell lymphoma, leg type
2
Q
What is the epidemiology of this lymphoma ?
A
- accounts for ~50% of primary cutaneous B cell lymphomas
- usually seen in middle aged adults
- M:F ratio of 1.5:1
3
Q
What is the typical site of involvement for PCFCL ?
A
- solitary or localized skin lesions
- scalp, forehead or trunk
- ~5% of cases with skin lesions on legs
- ~15% of cases with multifocal skin lesions
4
Q
What are the salient clinical features of
PCFCL ?
A
- firm, erythematous to violaceous plaques, nodules or tumors of variable sizes
- on the trunk the tumors may be surrounded by erythematous papules and sometimes plaques
- ulceration is rarely observed
- multifocal lesions are rare but when present do not portend a worse prognosis
- if untreated lesions increase in size but dissemination or extracutaneous site involvement is very rare
- recurrences are usually proximate to the initial cutaneous
5
Q
What are the microscopic findings in
the PCFCL ?
A
- typically have perivascular and periadnexal infiltrates with sparing of the epidermis -IMP
- spectrum of growth pattern (follicular, diffuse, etc)
- follicular growth pattern show nodular infiltrates in the dermis with extension into the subcutis
- cases with diffuse pattern show predominance of centrocytes, some of which may be spindled (KEY)
- there may be only focal FDCs by IHC
- diffuse pattern cases usually have a high proliferation index
6
Q
What are the morphologic differences
between PCFCL and cutaneous follicular hyperplasia ?
A
- PCFCL
- follicles may be poorly defined
- monotonous proliferation of BCL6+ follicle centre cells with an intact FDC meshwork highilighted by CD21 and CD23
- lack tingible body macrophages
- generally have an attenuated or absent mantle zone
- low proliferation rate
- reactive T cells and a prominent stromal component may be seen
7
Q
What is the immunophenotype of PCFCL ?
A
- (+) for CD79a and CD20
- but they are negative for Ig by IHC
- flow shows l.c. restriction in 3/4 cases
- (+) BCL6 (consistently +)
- CD10 may be positive in cases with a follicular growth pattern, but is generally negative in diffuse growth
- BCL2
- most cases do not express it or only show faint staining
- IMP: strong expression of BCL2 and CD10 should raise the suspicion of a nodular follicular lymphoma involving the skin
- (-)
- IRF4/MUM1 and FOXP1
- CD5 and CD43
8
Q
What is the postulated normal
counterpart to PCFCL ?
A
- mature germinal center B cell
9
Q
What is the status of the antigen receptor genes
in PCFL ?
A
- clonally rearranged IG genes
- somatic hypermutation is present but may not be detectable by PCR
10
Q
What are the typical cytogenetic abnormalities
and oncogenes in PCFCL?
A
- Rare BCL2 rearrangements ( do not usually see)
- only in the follicular growth pattern
- same gene expression profile as germinal center B cell subtype large B cell lymphomas
- In contrast to primary cutaneous Large B cell lymphoma, leg type
- inactivation of CDKN2A and CDKN2B on chromosome 9p21.3 is rarely identified
11
Q
What are the prognosis and predictive factors
for PCFCL ?
A
- Regardless of growth pattern, presence of t(14;18) and/or expression of BCL2, localized or multifocal skin lesions
- PCFCLs have an excellent prognosis
- 5 year survival rate of >95%
- BUT
- presentation on the leg has been shown to have a worse prognosis
- Cutaneous relapses occur in 30% of patients but do not represent progressive disease
- Systemic therapy is only warranted when:
- there is extensive cutaneous disease, extremely thick skin tumors, or extracutaneous disease
12
Q
A
