Lymphoma & related disorders

• Provisional entity within the category of splenic B cell lymphoma / leukemia, unclassifiable, along with hairy cell leukemia variant (Swerdlow: WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues, 4th Edition, 2017)
• Indolent disease course, often diagnosed at clinical stage IV disease (involvement of spleen, bone marrow and peripheral blood)
• Microscopically characterized by small to intermediate sized B lymphocytes diffusely invading the red pulp cords
  • Intrasinusoidal involvement can be seen on bone marrow biopsy
  • Peripheral blood smear reveals villous cytology
• Important to differentiate from hairy cell leukemia, hairy cell leukemia variant and splenic marginal zone lymphoma

• Requires constellation of clinical features, peripheral blood smear, marrow and spleen histology, immunophenotyping and cytogenetics
• Splenectomy may be is required for confirmation of diagnosis (Arch Pathol Lab Med 2014;138:1295)

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• Spleen:
  • Diffuse monomorphic involvement of the red pulp cords and sinusoids
  • Blood lakes lined by tumor cells may be present
  • Absence of white pulp involvement
    • May be residual lymphoid nodules composed of T cells or rare residual white pulp nodules (Am J Surg Pathol 2016;40:192)
    • Secondary effacement / obliteration of the white pulp may be seen (Blood Res 2018;53:74)
• Bone marrow:
  • Predominantly an intrasinusoidal infiltration; however, occasionally also includes interstitial and nodular infiltration
  • No lymphoid follicles have been reported, only mild fibrosis (Swerdlow: WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues, 4th Edition, 2017, Discov Med 2012;13:253)

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	Splenic diffuse red pulp small B cell lymphoma	Splenic marginal zone lymphoma	Hairy cell leukemia	Hairy cell leukemia variant
Frequency of non-Hodgkin lymphoma	0.5%	< 2%	2%	0.4%
Anemia and thrombocytopenia	Uncommon	Present (autoimmune)	Present	Present
Monocytopenia	Absent	Absent	Present (characteristic)	Absent (leukocytosis with lymphocytosis and normal monocyte count)
Blood smear	Broad based polar cytoplastic extensions (similar to splenic marginal zone lymphoma)	Polar villi and inconspicuous nucleoli	Reniform or oval nuclei, circumferential long villi, inconspicuous nucleoli	Abundant circumferential villi and prominent nucleoli
Spleen	Diffuse involvement of red pulp with cord and sinusoid infiltration, blood lakes may be present, absence of white pulp involvement	Micronodular pattern with white pulp replacement, marginal zone differentiation	Diffuse infiltrate in red pulp cords, effaced white pulp, formation of blood lakes	Red pulp involved, blood lakes uncommon, effaced white pulp with absent white pulp follicles.
TRAP	-	Variable	+	-
Bone marrow	Predominantly intrasinusoidal infiltrate, interstitial and nodular infiltration have been reported; no lymphoid follicles have been reported	Nodular interstitial and intrasinusoidal infiltrate; occasionally, tumor cells surround reactive follicles	Dense infiltrate, fibrosis	Interstitial and sinusoidal infiltrate
Flow cytometry	CD25- CD103- CD123-	CD25+ CD103 variable CD123-	CD25+ CD103+ CD123+	CD25- CD103+ CD123-
Immunohistochemistry	Annexin A1- DBA-44+	Annexin A1- DBA-44 variable	Annexin A1+ DBA-44+	Annexin A1- DBA-44+
Genetic mutation	CCND3 NOTCH1 MAP2K1 TP53	NOTCH2 VH1 / 2	BRAF V600E (~100%)	MAP2K1
Cytogenetics	Uncommon del 7q trisomy 18 del 17p	del 7q trisomy 3 (less common)	del 13q del 7q (uncommon)	del 17p
Treatment	Splenectomy	Splenectomy rituximab	Purine analogs rituximab	Partial response to purine analogs Splenectomy

A 60 year old man presents with abdominal discomfort and generalized weakness. CT of the chest / abdomen / pelvis reveals massive splenomegaly. Splenectomy demonstrates a monomorphic diffuse infiltration of the red pulp. Peripheral blood smear is shown above. Immunohistochemistry is positive for CD20 and DBA-44 and negative for CD25, CD103, CD123 and Annexin A1. What is the most likely diagnosis?

1. Hairy cell leukemia
2. Hairy cell leukemia variant
3. Splenic diffuse red pulp small B cell lymphoma
4. Splenic marginal zone lymphoma

C. Splenic diffuse red pulp small B cell lymphoma. While the 2017 revised WHO describes SDRPL as having a diffuse pattern of involvement of the red pulp with absence of the white pulp involvement (see table above), obliteration of the while pulp has been reported in the literature. As such, given the immunophenotype, a diagnosis of SDRPL is favored (Arch Pathol Lab Med 2014;138:1295, Haematologica 2010;95:1122, Discov Med 2012;13:253)

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Reference: Splenic diffuse red pulp small B cell Lymphoma

What is the most common treatment for splenic diffuse red pulp small B cell lymphoma?

1. Chemotherapy
2. Immunotherapy
3. Radiation
4. Splenectomy

D. Splenectomy

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Reference: Splenic diffuse red pulp small B cell Lymphoma