Perifollicular Lymphocytic Inflammation and Fibrosis in Dissecting Cellulitis: Evidence of a Consistent Histopathologic Pattern.

Active lesions (9/9) showed suppurative inflammation and remodeling superimposed on perifollicular infundibulo-isthmic lymphocytic inflammation and fibrosis (infundibulo-isthmic fibrosis, 9/9; lymphocytes, 8/9), with increased neutrophilic infiltrates (9/9 vs 0/9 in matched cNAS; adjusted P<0.001), granulation tissue (5/9 vs 0/9; adjusted P=0.035), and complete sebaceous gland loss (6/9 vs 0/9; adjusted P=0.012).

Infiltrates were CD4-predominant with prominent CD117-positive mast cells.

Perifollicular infundibulo-isthmic lymphocytic inflammation and fibrosis was observed in a sideburn biopsy in one patient, and 3 patients (25%) had concurrent histologic acne keloidalis nuchae.