[Morphology of mastocytosis]

Histochemical and electron-microscopic studies of skin biopsy specimens from 65 patients with mastocytosis have enabled the authors to classify the various mastocytoses (on the basis of infiltrate topography and structural features of mast cells) into macular, pustular, and nodular varieties of cutaneous mastocytosis (urticaria pigmentosa) and mastocytoma. No differences in mast cell structure were detected between cutaneous and systemic mastocytoses. Electron microscopically, mast cells in both appeared normal, with a predominance of granules having a fine-grained or homogeneous matrix and a small number of lamellar structures. In mastocytomas, on the other hand, ultrastructural changes and considerable degranulation were observed in the mast cells.