Vulvar hidradenitis suppurativa. Immunohistochemical evaluation of apocrine and eccrine involvement

OBJECTIVE: To evaluate the pathology of vulvar hidradenitis suppurativa (HS). STUDY DESIGN: A retrospective review of the histology of resections for vulvar HS was performed, and a battery of immunohistochemical stains was performed. They included markers of apocrine differentiation (GCDFP-15, CD15, lysozyme) and eccrine differentiation (GCDFP-15, S-100, CA-19.9, HMB45). RESULTS: Thirteen cases were available for review. Eccrine glands accounted for the majority of glands in all cases. Apocrine glands were not seen or were present only away from the area of active inflammation in 10 cases. In two cases, glands were totally destroyed in the areas of inflammation. Evidence of follicular obstruction was present in 11 of 13 cases. Severity of inflammation was variable, ranging from minimal, with burned-out disease, to severe. Fibrosis was variable but was greater with less inflammation, suggesting a later stage in disease evolution. Inflammation of the glands was often absent or minimal and seen only with associated poral occlusion. GCDFP-15 stained both apocrine and eccrine glands (only the dark cells). S-100 stained only the secretory (clear) cells of the eccrine glands. CD15 stained apocrine glands. Lysozyme stained apocrine glands, but this was not a consistent finding. CA19-9 gave inconsistent results in eccrine glands. HMB-45 was negative in all cases. CONCLUSION: Cases of vulvar HS showed a majority of eccrine glands in active areas. Apocrine glands, when present, were away from active inflammation. Inflammation and eventual destruction of glands appear to be a secondary part of the disease process. GCDFP-15 is a reliable marker for both apocrine differentiation and the dark cells of eccrine glands. S-100 is a reliable marker for the clear cells of eccrine glands. CD15 also was reliable for apocrine differentiation. Lysozyme showed weak apocrine staining. CA19-9 and HMB-45 were not reliable markers for apocrine or eccrine gland differentiation.