Chondrodermatitis nodularis chronica helicis (CNCH) is a common condition characterized by tender nodules of the helix, of uncertain mechanism. The pain is not explained by current physiopathological hypotheses.

We sought to investigate possible nerve hyperplasia in CNCH.

Thirty-seven cases of clinically typical CNCH were submitted to conventional microscopy after surgical excision and analyzed with immunohistochemistry using PS100 and neurofilament antibodies. As controls, we investigated 25 tumors of the ear with the same methods.

Large nerves (>0.1 mm in diameter) were seen in 8 of 37 cases; these were close to the cartilage or at the upper part of the ulceration. Increased numbers of small nerve sections (0.01-0.06 mm in diameter) were seen in 35 of 37 cases, with more than 20 sections per low-power field in 18 cases. Nerve hyperplasia was not observed in tumors of the ear, even in ulcerated cases.

Hypothesis based on morphologic observations.

Nerve hyperplasia is present in CNCH, but is often masked by intense vascular and inflammatory reactions. This finding may explain the induction of pain by light pressure, whereas ulcerated auricular malignant tumors are generally painless. Certain authors believe that CNCH is an equivalent of prurigo nodularis, which interestingly also shows nerve hyperplasia.