Telocytes are the common cell of origin of both PEComas and GISTs: an evidence-supported hypothesis.
Bottom Line: A fraction of GISTs was also found positive for CD63, a tetraspanin protein originally described in melanomas and marking exosomes. (2) c-KIT (CD117), proper of the vast majority of GISTs, can be expressed by PEComas (as well as by telocytes). (3) Markers described in telocytes (CD34, S-100, smooth muscle actin and vascular endothelial growth factor) have been reported as positive in cases of PEComas and GISTs.Telocytes show distinctive ultrastructural features with thin, extended, telopodes and are likely involved in inter-cellular signalling via paracrine secretion as well as by shed vesicles and exosomes.These cells have been described in many locations (cavitary and non-cavitary organs) and might display potentialities of a wide spectrum of differentiation (and function).
Affiliation: Victor Babes Institute, Bucharest, Romania Department of Biomedical Sciences and Human Oncology, University of Turin, Turin, Italy.Show MeSH
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Mentions: We first checked in GISTs for the presence of melanoma markers, which are regarded as diagnostic of PEComas. In a preliminary study on 10 cases of GIST, none was found positive for HMB45. We then tested additional melanoma markers on a selected tumour series (Table 1) and 58.33% were found positive for MiTF (14 out of 24 cases of GISTs of the spindle, epithelioid or mixed type) and 68.18% were positive for CD63 (15 out of 22 tested cases). The staining was either limited to a few dispersed cells or extended to the vast majority of tumour cells (Fig. 1A and B). The kidney PEComas tested for CD63 were also positive, similar to other melanocytic markers.
Affiliation: Victor Babes Institute, Bucharest, Romania Department of Biomedical Sciences and Human Oncology, University of Turin, Turin, Italy.