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Letter to the Editor

Ann Lab Med 2022; 42(5): 606-608

Published online September 1, 2022 https://doi.org/10.3343/alm.2022.42.5.606

Copyright © Korean Society for Laboratory Medicine.

Platelet Satellitism: Just a Laboratory Curiosity? A Case Report of Platelet Satellitism with Multilineage Involvement

Antonio La Gioia, M.D.1 , Fabiana Fiorini, Ph.D.2 , and Marcello Fiorini, M.D.2

1Docemus, Laboratory Medicine, Torrevecchia Teatina, Italy; 2UOC Medicina di Laboratorio Azienda Usl Nord Ovest, Pontedera, Italy

Correspondence to: Antonio La Gioia, M.D.
Docemus, Laboratory Medicine, Via Valleparo 8, 66010 Torrevecchia Teatina, Italy
Tel: +39-3281186642, Fax: +39-0587-350769
E-mail: ant.lagioia@gmail.com

Received: September 6, 2021; Revised: December 30, 2021; Accepted: March 14, 2022

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Dear Editor,

Platelet satellitism (PS) is a rare cause of pseudothrombocytopenia due to the adhesion of platelets to the surfaces of circulating leukocytes. PS occurs when circulating auto-antibodies bind to cryptic antigens exposed because of the calcium-chelating activity of EDTA [1]. The antibody–platelet antigen (antiglycoprotein IIb/IIIa) binds to the Fcγ receptor (CD16) on the cell surface, resulting in the typical PS results in blood smear images [2]. PS can be associated with platelet phagocytosis by neutrophils or, less frequently, monocytes [3]. PS accounts for less than 1% of total pseudothrombocytopenia cases. The reported yearly incidence of 1:12,000 may be underestimated as PS does not cause remarkable scattergram abnormalities in most cases and is usually detected using light microscopy [2]. We report a case of PS around neutrophils, monocytes, and lymphocytes, associated with platelet phagocytosis. The requirement for informed consent was waived by the Institutional Ethics Committees because of the retrospective nature of this study based on a case that occurred in 2017.

A 42-year-old asymptomatic woman presented at Livorno hospital as an outpatient with thrombocytopenia (50×109/L; reference range [RR], 150–400). The Hb concentration was 132 g/L (RR, 114–150), and the leukocyte count was 4.99×109/L (RR, 4.0–11.0). A differential leukocyte count showed (×109/L): neutrophils, 0.9 (RR, 1.8–6.7); lymphocytes, 2.6 (RR, 1.1–3.7); monocytes, 1. 2 (RR, 0.8–1.0); eosinophils, 0.22 (RR, 0.05–0.65); and basophils, 0.07 (RR, 0.00–0.10).

A blood smear review revealed that 100% of neutrophils, 27% of monocytes, and 7% of lymphocytes had from one to more than 20 platelets adhering to the cell surface (Fig. 1A–D, E–J, and K, L, respectively). Approximately 61% of lymphocytes were large granular lymphocytes, 6% of which were PS-positive (Fig. 1L), and a few small lymphocytes exhibited unique platelet adhesion (Fig. 1K). This is the only case described to date in which PS affected four different cell types. Platelet phagocytosis was detected in 20% of neutrophils and 6% of monocytes with PS. Moreover, aspects of pre-phagocytosis and post-phagocytosis (i.e., platelets housed in a pocket on the cell surface and empty vacuoles) were frequently observed.

Figure 1. Platelet satellitism and phagocytosis. ×1,000 magnification. Satellitism seen around neutrophils (A-D), monocytes (E-J), lymphocytes (K), and large granular lymphocytes (L). Damaged neutrophils (C, D) show significantly more sticky platelets than intact ones. Platelet phagocytosis is seen for neutrophils (B, D) and monocytes with pre- and post-phagocytic aspects (F-H and I, J, respectively).

Neutrophils with cytoplasmatic breaks due to damage caused during peripheral blood smear preparation showed significantly more adherent platelets than undamaged cells (Fig. 1C, D). The exposure of a higher number of Fcγ receptors due to cell membrane lesions may explain the polarization of platelets. As a sodium citrate tube for coagulation testing was available, we were able to repeat the cell count and microscopic review, which revealed a platelet count close to the reference value (147×109/L) and the absence of satellitism. Thus, satellitism-related EDTA-dependent PTCP was diagnosed.

After the first reports of platelet adherence to polymorphonucleated cells, the majority of reports mainly described neutrophils. The only case of PS around basophils was described by Liso, et al. [4] in 1981. Fábryová, et al. [5] and Lazo-Langner, et al. [6] each described two cases involving eosinophils. Ravel and Bassart [3], Cesca, et al. [7], and Español, et al. [8] reported satellitism to monocytes, lymphocytes, and large granular lymphocytes, respectively. Table 1 summarizes the reported cases of PS involving monocytes or lymphocytes and those involving two or three different cell types simultaneously. Numerous cases also involved platelet phagocytosis, mainly by neutrophils (case 4, 8, 10, 13, 20, 21, 28), monocytes (case 25), or both neutrophils and monocytes (case 1, 2, 12, 16, 27). In cases diagnosed as having lymphoma or a lymphoproliferative disorder, the cells involved in PS were atypical lymphocytes (case 11, 15, 17, 19, 22, 24, 26), large granular lymphocytes (case 9), or normal lymphocytes (case 18, 23).

Table 1 . Reported cases of PS and satellitism/phagocytosis association during 1974–2020. Isolated neutrophilic satellitism has not been reported

Case No.SatellitismPhagocytosisReported clinical conditions/diagnosis/disease*Reported cases: First author, Journal, Year [ref in the text]
1NE, MONE, MONDRavel, Lab Med, 1974 [3]
2NE, MONE, MOPneumoniaGreipp, Blood, 1976
3MONOHypo gamma globulinDjaldetti, Scan J Haematol, 1978
4NENEMalignant lymphomaWhite, Am J Hematol, 1978
5–7MONOPV, MPD, CLLCohen, Acta Haemat, 1980
8NENEPelvic inflammationYoo, Acta Haemat, 1982
9NE/LGLNONDEspañol, Haematologica, 2000 [8]
10NENENHLee, Arch Pathol LabMed, 2000
11AtyLYNOMCCesca, Haemapathol, 2001 [7]
12NE, MONE, MONDCriswell, Am J Clin Pathol, 2001 [9]
13NENENDSenzel, Blood 2013
14NE, EO, MONOVasculitisLazo-Langner, Am J Hematol, 2002 [6]
15AtyLYNOMZLatger-Cannard, Eur J Haematol, 2009
16NENE, MONDCampbell, Am J Hematol, 2009
17AtyLYNOMZMontague, Ann Diagn Pathol, 2013
18LYNONDTun, Indian J Hematol Blood Transfus, 2013
19AtyLYNONHQuiròs, Rev Lab Clin, 2013
20NENENDYoon, Lab Med Online, 2013
21NENETongue malignancyPaul, Indian J Hematol Blood Transfus, 2013
22AtyLYNOMZDegaud, IJLH, 2018
23LYNONDLopez-Molina, IJLH, 2018 [109]
24AtyLYNOB-LPDZhu, Blood, 2018
25MOMOHBain, Am J Hematol, 2018
26AtyLYNONHGatignol, Ann Biol Clin, 2019
27NE, MONE, MOInfectionAmoureaux, Morphologie, 2020
28NENEPancreatic carcinomaSousa, Platelets, 2020

*Reported cases of platelet satellitism/phagocytosis (all cell types) and satellitism around monocytes, lymphocytes and large granular lymphocytes (by year of publication from 1976 to 2020; PubMed, August 31, 2021; keywords used: “pseudo thrombocytopenia,” “platelet satellitism,” “platelet phagocytosis”).

Abbreviations: PS, platelet satellitism; NE, neutrophils; EO, eosinophils; MO, monocytes; LY, lymphocytes; AtyLY, atypical lymphocytes; LGL, large granular lymphocytes; PV, polycythemia vera; MPD, myeloproliferative disorder; CLL, chronic lymphocytic leukemia; NO, absence of phagocytosis; ND, not defined; NH, non-Hodgkin lymphoma; MC, mantle cell lymphoma; MZ, marginal zone lymphoma; B-LPD, B-lymphoproliferative disease; H, Hodgkin lymphoma.



Criswell, et al. [9] reported that in the case of PS, the “greatest clinical relevance is spurious reporting that can lead to unnecessary treatment of thrombocytopenia”; however, the involvement of atypical lymphocytes in most cases of lymphoid neoplasms should be considered a potential non-casual association. Therefore, the recommendation to check platelet counts while simultaneously evaluating for a possible lymphoproliferative disorder is entirely acceptable in cases of PS involving lymphocytes [10].

We thank Dr. Miriam Conte for English language revision of the manuscript.

All three authors contributed to the conception and design of the study. Fiorini F and Fiorini M were involved in clinical evaluation and interpreted the results. La Gioia A supervised the study. All authors read and approved the final manuscript.

The authors declare that they have no conflicts of interest.

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