Table 2.
List of circulating rare cells.
| CRC Type | Description | Cell Concentration per mL | Clinical Usefulness (cbLB) | References |
|---|---|---|---|---|
| Megakaryocyte-Erythrocyte Progenitors | Bone marrow dwelling megakaryocyte progenitor | N.A. | Therapy: thrombocytopenia | [46,48,49] |
| Naked Megakaryocyte | Large bare lobulated nuclei with high density DNA | <25 | (I) solid tissue cancer prognosis | [11] |
| Cytoplasmic Megakaryocyte | Largest circulating round cell being original megakaryocyte containing platelet load | <0.5 | (I) Therapy: thrombocytopenia (ii) Diagnostic biomarker and therapy intervention target in myeloproliferative disorders (iii) prediction of bone metastasis |
[17,20,21,46,48,49] |
| Mature Endothelial phalanx cell | Cobblestone-like quiescent cells | <100 cells (0.5 to 3 on average) * | (I) Prognosis, Predictive biomarker Solid tissue cancer by marker elevation | [34,68,76,94] |
| Mature Endothelial tip cell | Larger activated cell status | |||
| Mature Endothelial sprout cell | Larger, activated cell status | |||
| Endothelial progenitor cell | Bone marrow-derived | 140–360 (early EPC) <1 (late EPC) ** |
(I) therapy: coronaryartery disease, neo or re vascularization (ii) prediction biomarker myocardial infarction, pulmonary hypertension and diabetes II, atherosclerotic disease progression etc. |
[68,74,94,100] |
| Erythroblasts -Normoblast | Small late matured erythroblast | <50 | (I) Predictive biomarker for leukemia (ii) Prediction of death in critical ill patients |
[2,118,122] |
| Erythroblast - Baso-Eb, Poly-Eb | Larger cells with lower N/C ratio | <0.5 | [10] | |
| Fibroblast like cells/Fibrocytes (CD45+) | Rare elongated spindle-shaped leukocyte | <5000 | (I) prediction of pulmonary fibrosis | [138,150] |
| Fibroblast like cells/Fibrocytes (CD45−) | Rare elongated spindle-shaped fibrocyte subpopulation (activated?) | 250 *** | unknown | [134] |
| Fibroblast-like cells/myofibroblast (hematopoietic lineage) | Activated fibrocyte differentiated into tissue resident contractile cell type | unknown | (I) predictive biomarker myocardial infarction | [186] |
| Fibroblast-like cells/mesenchymal stem cells | Bone marrow derived cell | <10 | (I) Prognosis and predictive biomarker in many pathologies e.g., cancer, polytrauma (II) fetal cell marker |
[181,183] |
| Fibroblast-like cells/myofibroblast (mesenchymal lineage) | Activated MSC or fibroblast differentiated into tissue resident contractile cell type | unknown | (I) predictive biomarker for solid tissue cancer (ii) therapeutic target in cancer (iii) stem cell therapy for bone and cartilage repair |
[194,198] |
| Hematopoietic stem cell | Uncommitted quiescent small blastoid cells type | <1000 | To be researched | [212,224] |
| Very small embryonic stem cells | Smallest rare cell subset with high density nucleus | <350 | (I) Predictive marker diaease non-specific (ii) age/lifestyle marker (iii) stem cell therapy |
[203] |
| Mature Epithelial cells type 1 | Large squamous, columnar, cuboidal shaped cells with very low N/C-ratio | Unknown | Not investigated | |
| Mature epithelial cell type 2 | Round or oval blastoid like cells with low N/C ratio= “CellSearch CTC” | 0.42 cells (average of reports) | (i) prognosis, prediction in solid tissue cancer | [1] |
| Circulating epithelial progenitor cells | Round blastoid cells | Unknown | Pulmonary disorder | [146] |
| Hemangioblast | Small blastoid round cells (similar to VSELS) | Unknown | Not specified | [237] |
| CH-Cells | Small blastoid cells | Unknown | Not specified | [241] |
| extravillous trophoblasts | Large irregular shaped blastoid cells | <0.5 cells | Fetal origin | [242] |
* no distinction between activated and quiescent mature endothelial cells, and microscopy range in brackets; ** estimated from cultivating cells reported by Lin et al. [87]; *** cell type unknown in peripheral blood concentration is estimated from report about ratio between CD45+ and CD45− fibrocytes by Suga et al. [134] reporting 5% frequency when referred to CD45+ fibrocytes.