Author: Dr Ben Tallon, Dermatologist/Dermatopathologist, Tauranga, New Zealand, December 2016.
Histology of focal mucinosis
Lesions of focal mucinosis present with a dome shaped elevation of the skin and a circumscribeddermal pool of mucin (figures 1, 2). Involvement of the subcutaneous tissue is uncommon. A delicate infiltrate of fibroblasts and an increase in capillary vessels can be seen within the lesion (figures 3, 4).
The mucin stains with colloidal iron (blue-green), and Alcian blue at pH 2.5 (blue) (figure 5).
Differential diagnosis of focal mucinosis
Papular mucinosis of lichen myxoedematosus requires clinical correlation as histolocically it may appear identical. There may be increased fibroblastic proliferation and fibrosis.
Generalised and pretibial myxoedema: These conditions are associated with thyroid disease. There is mucin deposition in the dermis without fibroblast proliferation. Epidermal changes may include hyperkeratosis and follicular plugging.
Weedon’s Skin Pathology (Third edition, 2010). David Weedon
Pathology of the Skin (Fourth edition, 2012). McKee PH, J. Calonje JE, Granter SR