Flow cytometric analysis of fine needle aspirates is affected by tumor subtype, but not by anatomic location nor technique

Abstract

BackgroundCurrent clinical practices are shifting towards utilizing less invasive biopsy techniques, including fine needle aspiration (FNA) and needle core biopsies. If a patient has a suspected hematologic malignancy, a portion of the FNA sample is typically submitted for flow cytometry (FC) analysis, providing valuable immunophenotypic data.MethodsFNA specimens were identified via a pathology database search. All cases were morphologic evaluated and a subset of cases were analyzed by FC.Results245 hematologic FNA specimens were identified; 84% of these cases had an adequate number of cells for FC analysis, and an unequivocal morphologic diagnosis (benign or malignant) was rendered in 85%. The percentage of cases with an unequivocal diagnosis was statistically significantly higher in those with associated FC than with those without FC (90% vs 58%). Neither FNA technique nor anatomic site affected the likelihood of obtaining an adequate sample for FC analysis and/or rendering a definitive morphologic or unequivocal FC diagnosis. Likewise, tumor subtype did not affect the likelihood of acquiring enough cells for FC analysis, but occasionally resulted in equivocal FC diagnoses or discordant FNA and FC diagnoses. Aggressive B‐cell lymphomas and Hodgkin lymphomas were significantly less likely to be detected by FC as compared to low‐grade B‐cell lymphomas. Discrepancies between FNA and FC diagnoses occurred in 13% of cases. The majority of discrepancies (78%) included FC false negatives, while only 22% of cases had atypical or positive FC with negative FNA.ConclusionsFNA with associated FC is a powerful diagnostic technique; however, lymphoma subtype may affect diagnostic sensitivity by FC, and therefore, discordant FNA and FC results should be interpreted with caution.

Factors determining whether diffuse large B‐cell lymphoma samples are detected by flow cytometry

“…That study reported that samples from extranodal sites were more likely to be missed by FCM than nodal samples 13 . By contrast, the current study found that the site of collection did not influence the likelihood of detection of DLBCL by FCM, consistent with the findings of a recent study 7 …”

“…13 By contrast, the current study found that the site of collection did not influence the likelihood of detection of DLBCL by FCM, consistent with the findings of a recent study. 7 Fibrosis, necrosis and apoptosis are known to occur commonly in DLBCL 10,12 and may impair the capacity to detect lymphoma cells by FCM. In a previous study, necrosis was reported to be associated with a higher likelihood of missing DLBCL by FCM.…”

“…Detection and subtyping MBN remains a diagnostic challenge with overlapping and heterogeneous characteristics within and between each subtype. While diagnosis and classification are traditionally based on microscopy, immunophenotyping by flow cytometry (FCM) is established as a crucial part of the diagnostic workup of MBN 2 and is particularly useful as an ancillary test for fine‐needle aspirates (FNA) 3–8 …”

“…FCM is particularly useful in differentiating between reactive and lymphomatous processes, especially low‐grade lymphomas, as such distinction is often difficult with microscopy alone 6,8 . The diagnostic power of FCM in different MBN subtypes is variable and high‐grade B‐cell lymphomas such as DLBCL are more often missed by FCM 7,9–11 …”

“…6,8 The diagnostic power of FCM in different MBN subtypes is variable and high-grade B-cell lymphomas such as DLBCL are more often missed by FCM. 7,[9][10][11] There are a number of reports linking the characteristics of DLBCL to its difficulty in being detected by FCM. It has been proposed that an increase in apoptosis or necrosis in large B-cell lymphomas compromises detection by FCM.…”