Multisite marrow sampling may sharpen cytology in dogs

A new canine bone marrow study points to a simple but potentially important change in diagnostic practice: sample more than one site. In a paper described as showing that multisite sampling improves consensus cytologic interpretation in dogs, investigators examined whether a single marrow site can produce an unrepresentative read, an issue with obvious implications for dogs being worked up for hematologic abnormalities. The core message is straightforward: when marrow disease is unevenly distributed, one sample may not tell the whole story. (experts.illinois.edu)

That question has been building for some time. Bone marrow evaluation is a cornerstone test in dogs with unexplained anemia, thrombocytopenia, leukopenia, suspected leukemia, myelodysplastic change, or infiltrative disease, and both aspirates and core biopsies are used because they answer somewhat different questions. Existing veterinary guidance has long noted that marrow interpretation depends heavily on sample adequacy, blood contamination, and correlation with the CBC and clinical picture. (tvmdl.tamu.edu)

What’s changed is the stronger evidence that marrow heterogeneity is not just a theoretical concern. A related 2026 study from overlapping investigators at the University of Illinois evaluated four core biopsy sites in 16 dogs with suspected hematologic disease: both proximal humeri and both iliac crests. Two board-certified clinical pathologists reviewed 64 masked samples, and the authors found that moving from one to two sites improved diagnostic capture from 76.6% to 94.8% under a permissive rule, with similarly meaningful gains under a stricter agreement standard. They also reported site-specific differences in myeloid-to-erythroid ratios and megakaryocyte counts, plus modest inter-pathologist agreement overall, underscoring that both sampling location and interpretation variability can affect the final diagnosis. (experts.illinois.edu)

That biopsy paper matters here because the authors explicitly said bone marrow aspirates were collected during the same procedures, but the cytologic findings were being reported separately. In other words, the new cytology-focused report appears to be the companion piece to that earlier biopsy analysis. That connection helps frame the latest study as part of a broader effort to test whether current single-site marrow practices are missing clinically relevant disease in dogs. (pmc.ncbi.nlm.nih.gov)

There’s also some wider context for why this resonates. A recent Texas A&M Veterinary Medical Diagnostic Laboratory review stated that complete marrow evaluation should include history, a contemporaneous CBC, a marrow aspirate, and a core biopsy. Older reviews similarly stress that cytology is essential for differential cell assessment, while histology adds architectural information and can better characterize fibrosis or infiltrative change. If multisite cytology improves consensus interpretation, that could strengthen the case for tailoring aspirate strategy more deliberately rather than defaulting to a single convenient site. (tvmdl.tamu.edu)

Expert reaction specific to the new cytology paper was limited in publicly indexed sources, but the broader literature supports the concern about sampling error. In the biopsy companion study, the authors concluded that the biggest practical benefit came from adding a second site, not necessarily from sampling all four. They also acknowledged tradeoffs, including small sample size and procedural complexity, while still arguing that the additional effort may be justified by improved diagnostic accuracy. Separately, published veterinary literature on marrow sampling complications suggests the procedure is generally useful but not trivial, which means clinicians will likely weigh diagnostic yield against anesthesia time, patient stability, and operator experience. (experts.illinois.edu)

Why it matters: For veterinarians, clinical pathologists, and specialty teams, this is less about changing every marrow workup overnight and more about identifying where single-site sampling is most vulnerable. Dogs with suspected focal marrow disease, discordant clinicopathologic findings, nondiagnostic first aspirates, or persistent suspicion despite an apparently bland sample may be the clearest group to benefit from a second site. The study also reinforces a broader diagnostic principle: a normal or equivocal marrow result may reflect where the needle went, not just what disease is present. (experts.illinois.edu)

What to watch: The next step is whether the full cytology paper, and any commentary that follows, can define a practical decision framework, such as when to add a contralateral or alternate-site aspirate, whether particular diseases show more heterogeneity, and how multisite sampling affects turnaround, cost, sedation planning, and diagnostic confidence in day-to-day practice. (experts.illinois.edu)