What Does Presence Of Mast Cell In CBC Test Indicate?

Hi, I have a 14 yr old son who has been being followed by a hematologist for 9 months for mild thrombocytopenia and mild neutropenia. His only clinical symptom is fatigue. A BMB has not been performed. His DR thinks its either ITP, or less likely, familial or a bone marrow failure. I am a Med tech and I occasionally check his CBC. Last time I looked at his smear, I found a mast cell. Is this significant? Could this be a clue to what's going on with him? Should I wait 2 more months for his next appointment, or go in earlier? Thank you.