[1348] Normal Splenic Lymphoid Subsets Mimic Aberrant Antigen Expression

Nidhi Aggarwal, Jason Fischer, Steven H Swerdlow, Fiona E Craig. University of Pittsburgh School of Medicine, Pittsburgh, PA

Background: Flow cytometry (FC) assists in the diagnosis of lymphoma through identification of aberrant antigen expression. However, normal lymphoid subsets with less well-recognized phenotypes can mimic lymphoma. This study characterizes lymphoid subsets in normal spleen using 8-color FC.
Design: 20 spleens removed for traumatic rupture, with cell viability >50%, were analyzed within 24 hrs with the following FC combinations: CD16&57/CD7/CD4/CD2/CD56/CD3/CD5/CD8; K/λ/CD5/CD19/CD10/CD38/CD20/CD45; αβ/γδ/CD3/CD25 and CD14/CD13&33/CD45/CD34.
Results: This study reveals the normal variation in splenic lymphoid subsets (Table) and demonstrates some subsets with phenotypes that have been associated with lymphoid neoplasms.
Well recognized lymphoma-associated phenotypes identified in this study include CD7- T-cells and CD5+ B-cells.
Less-well recognized phenotypes encountered in all cases, except as indicated, include: CD5- to dim+ CD8+ T-cells, CD3+ bright (br.) γδ T-cells (15/20), CD5- γδ T-cells (Fig. 1a), CD2- NK-cells and CD7+dim NK-cells (Fig 1b). The latter two NK-cell phenotypes were seen more often in the mature subtype (p<0.01).

Population (Parent)	% of Parent Indicated
	Median	Min	Max
T cells (Lymphoid cells)	34	21	55
CD4+ (T cells)	56	37	78
CD8+ (T cells)	33	13	46
CD4/CD8 ratio	1.7	0.9	6
CD4+ CD8+ (T cells)	3	1	12
CD4- CD8- (T cells)	7	1	19
αβ+ (T cells)	93	79	99
γδ+ (T cells)	5	0.5	19
CD7- (T cells)	11	6	19
CD5- (γδ T cells)	16	5	82
CD5- (CD8+ T cells)	5.5	2	30
CD25+ (T cells)	32	18	52
NK cells (Lymphoid cells)	7.7	4	18
CD2- (NK cells)	36	23	53
Immature, CD56+br. CD16&57- (NK cells)	51	25	74
Mature, CD56+dim CD16&57+br. (NK cells)	29	13	63
Int., CD56+br. CD16&57+dim (NK cells)	10	4	23
B-cells (Lymphoid cells)	46	30	67
CD10+ (B cells)	3.5	1	24
CD5+ (B cells)	8.5	1	15
κ/λ ratio	1.2	0.9	1.8
Plasma cells (Total cells)	0.2	0.1	0.9

Conclusions: 8-color FC analysis of normal spleen demonstrates lymphoid phenotypes that may resemble those described in subtypes of lymphoma, such as LGL leukemia, hepatosplenic lymphoma, and chronic NK-cell lymphoproliferative disorders. Familiarity with these normal phenotypes can help prevent misinterpretation. Furthermore, these findings support that these neoplastic phenotypes reflect expanded normal subsets rather than aberrant antigen expression.
Category: Hematopathology

Monday, March 19, 2012 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 229, Monday Morning