Immunohistochemical analysis of cytokeratin expression in reactive eccrine syringofibroadenoma‐like lesion: a comparative study with eccrine syringofibroadenoma

In addition to solitary eccrine syringofibroadenoma (ESFA), there is another type of ESFA which is associated with underlying dermatoses (reactive ESFA-like lesion). Five lesions in 4 patients of reactive ESFA-like lesion were analyzed by an immunohistochemical method using 13 kinds of anti-cytokeratin (CK) antibodies. Two cases of solitary ESFA were also studied by the same procedure for comparison. Suprabasal staining pattern of AE1 and MNF116, which stain CKs 6, 16 and 17, markers of hyperproliferative state, was observed diffusely in 5 lesions of reactive ESFA-like lesions except for focal negative staining in one case, and was observed focally in one case of solitary ESFA. Furthermore, differentiation-specific cytokeratin expression was reduced in 3 of 5 lesions of reactive ESFA-like lesions. Both ESFA and reactive ESFA showed basically similar immunoreactivity suggesting differentiation toward the dermal duct. The above slight difference in immunoreactivity between both lesions may be explained due to inflammatory infiltrates associated with underlying dermatoses.