ORIGINAL ARTICLE

Mast cell distribution in normal adult skin

A S Janssens^1,4, R Heide¹, J C den Hollander², P G M Mulder³, B Tank¹ and A P Oranje¹

¹ Department of Dermatology and Venereology, Erasmus MC, PO Box 2040, 3000 CA Rotterdam, The Netherlands
² Department of Pathology, Erasmus MC
³ Department of Epidemiology and Biostatistics, Erasmus MC
⁴ Department of Dermatology, LUMC, 2333 ZA Leiden, The Netherlands

Correspondence to:
Correspondence to:
Dr A P Oranje
Department of Dermatology and Venereology, Room Pb 112, Erasmus MC Rotterdam, PO Box 2040, 3000 CA, The Netherlands; a.p.oranje{at}erasmusmc.nl

Aims: To investigate mast cell distribution in normal adult skin to provide a reference range for comparison with mastocytosis.

Methods: Mast cells (MCs) were counted in uninvolved skin adjacent to basal cell carcinomas and other dermatological disorders in adults.

Results: There was an uneven distribution of MCs in different body sites using the anti-tryptase monoclonal antibody technique. Numbers of MCs on the trunk, upper arm, and upper leg were similar, but were significantly different from those found on the lower leg and forearm. Two distinct groups were formed—proximal and distal. There were 77.0 MCs/mm² at proximal body sites and 108.2 MCs/mm² at distal sites. Adjusted for the adjacent diagnosis and age, this difference was consistent. The numbers of MCs in uninvolved skin adjacent to basal cell carcinomas and other dermatological disorders were not different from those in the control group. Differences in the numbers of MCs between the distal and the proximal body sites must be considered when MCs are counted for a reliable diagnosis of mastocytosis. A pilot study in patients with mastocytosis underlined the variation in the numbers of MCs in mastocytosis and normal skin, but showed a considerable overlap. The observed numbers of MCs in adults cannot be extrapolated to children.

Conclusions: MC numbers varied significantly between proximal and distal body sites and these differences must be considered when MCs are counted for a reliable diagnosis of mastocytosis. There was a considerable overlap between the numbers of MCs in mastocytosis and normal skin.

Abbreviations: ATA, anti-tryptase monoclonal antibody; BCC, basal cell carcinoma; MC, mast cell; PBS, phosphate buffered saline

Keywords: tryptase monoclonal antibody; body sites; immunohistochemistry; mast cell; mastocytosis

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