[Congenital preauricular fistula infection: a histopathology observation]

To investigate the pathology characteristics of congenital preauricular fistula with infection, in order to reduce the recurrence rate after surgery and improve operative technique.

Twenty-five patients diagnosed as congenital preauricular fistula with infection were analyzed. There were 14 patients in infection history group, 9 in infective stage group, and 2 in recurrence group respectively. The whole piece of fistula and scar tissue was completely excised during operation. The specimens were observed by naked eye and serial tissue sections were analyzed.

(1) Macroscopically, in infection history group, initial morphology can be maintained near the fistula orifice, but the distal tissue was dark red scar tissue. In infective stage group, the distal tissue of the specimens was granulation tissue and cicatricial tissue. The granulation tissue was crisp and bright red. In recurrence group, multicystic lesions with severe edema was observed, with a classical dumb-bell appearence. (2) Microscopically, in infection history group and recurrence group, we can see that the distal fistula tissue was discontinuous and was separated by scar tissue. In infective stage group, we can find neo-angiogenesis and infiltration of plasma cells, lymphocytes, neutrophil between interrupted fistula tissues. (3) All patients were followed up for 6-12 month, without recurrence.

The fistula tissue of congenital preauricular fistula with infection was divided by the scar tissue, and they did not communicate with each other. Complete delineation of fistula is hardly achieved by methylene blue staining. Radical excision of the fistula and scar tissue may help to avoid leaving viable squamous epithelial remnants and reduce the recurrence rate.