Table 1. World Health Organization clinical staging system for mast cell tumors.

Stage	Description
I	One tumor confined to the dermis, without regional lymph node involvement 1. Without systemic signs 2. With systemic signs
II	One tumor confined to the dermis, with regional lymph node involvement 1.Without systemic signs 2. With systemic signs
III	Multiple dermal tumors; large, infiltrating tumors with or without regional lymph node involvement 1. Without systemic signs 2. With systemic signs
IV	Any tumor with distant metastasis, including blood or bone marrow involvement