Basophilia is defined as an absolute blood basophil count greater than 0.1 × 109/L [1]. It is a rare finding with a clear association with chronic myeloproliferative neoplasms, in particular chronic myeloid leukemia. Values above a cutoff point of 0.4 × 109/L are highly specific for hematological malignancies [2]. Therefore, recognizing basophilia is of clinical relevance.

However, the coefficient of variation of hematological counts in basophil counts is high (i.e., roughly 25%); ADVIA is one of the most imprecise [3]. In ADVIA 2120, the search for basophils is performed using cells that remain intact when they are exposed to phthalic acid and a surfactant. There are abnormal cells that are resistant to lysis with these agents, and conglomerates of nuclei can manifest as basophils [4]. This situation explains the high level of detection of increased basophils, even though they are not detected in peripheral blood smears, a phenomenon known as pseudobasophilia. This phenomenon has been described primarily in association with hematological malignancies [5, 6]. A new association is described below.

A 42-year-old male reported the onset of erythematous skin lesions with an axial and acral distribution that involved approximately 25% of his total body. An imaging study with PET/CT was performed that revealed evidence of supra and infra-diaphragmatic adenopathies, diffuse bone marrow metabolism, and gastric compromise. An automated hematological count was performed, which revealed a hemoglobin level of 13.7 g/dL, a platelet count of 164 × 103/µL, and a leukocyte count of 10,950 × 103/µL, the presence of large unstained cells (17% of cells), and 5% basophils (Fig. 1). When we examined the Baso cytogram, we noted a heterogeneous accumulation of cells in the Baso region, slightly to the right of the valley of mononuclear and polymorphonuclear cells. A peripheral blood smear using Cellavision revealed a high percentage of flower cells (Fig. 2) and no basophils. HTLV1 serology returned a positive diagnosis. Skin and gastric biopsies were performed and were consistent with a diagnosis of acute-phase adult T-lymphoma leukemia (ATLL).

Fig. 1
figure 1

Cytogram in ADVIA 2120: Baso channel (an increase in events is indicated in yellow and cyan; these cells are recorded as basophils, but they are suspected to be lymphoma cells) and Perox channel (an increase in events is shown in cyan; these cells are recorded as large unstained cells, but they are suspected to be lymphoma cells). Large unstained cells are large peroxidase-negative cells

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Fig. 2
figure 2

Flower cells in peripheral blood imaged using Cellavision. A manual count of basophils revealed zero

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Pseudobasophilia, more than a laboratory artifact or a counting error, should always be considered a red flag in the presence of suspicious cells that are positioned in a region occupied by basophils. Considering the low incidence of true basophilia, a search for atypical cells should always be conducted first. In addition, the location of these cells with respect to the nuclear lobularity is indicative of the cause: in this particular case, it indicates large lobulated nuclei, as detected in the smear. Adult T-lymphoma leukemia is a rare disease, and few reports have provided accurate diagnostic tools. Morphology is a valuable diagnostic tool that guides disease staging and serves as a relevant prognostic factor [7]. The morphological correlations observed using the ADVIA system warrant further evaluation as a potential diagnostic and prognostic factor.