Squamous cell carcinoma of the external ear: a clinico-pathological study of 8 Japanese patients

Squamous cell carcinoma arising in sun-damaged skin has been reported to have a very low incidence of metastasis. However, squamous cell carcinoma of the external ear, which is also considered to be one of the ultraviolet light-induced squamous cell carcinomas, has a relatively high propensity to metastasize and to recur locally. The purpose of this study was to clarify the clinical and pathological characteristics of squamous cell carcinomas of the external ear. Eight Japanese patients treated in our hospital were reviewed. The tumors had developed on the uppermost portion of the helix in half of the patients, and on the middle portion of the anthelix in the remainder. Histologically, all lesions penetrated to Clark's level TV or V. However, the vertical tumor thickness measured with an ocular micrometer was less than 4 mm in half of them and none of the lesions exceeded 10 mm in the thickness. Flow cytometric DNA content-analysis of the paraffin-embedded specimens revealed that 2 out of the 8 squamous cell carcinomas (25.0%) showed DNA aneuploidy and the residual 6 squamous cell carcinomas showed a diploid pattern alone, which is comparable to cutaneous squamous cell carcinomas in other regions. The present study revealed that squamous cell carcinomas of the external ear preferentially arise on a specified portion of the auricle and invade the deep dermis close to the underlying cartilage even though the lesions are thin. These results indicate that the higher metastatic potency of auricular squamous cell carcinomas is not because of the higher frequency of DNA-aneuploidy but because of the deep dermal invasion suggesting that the resection of the cartilage is required.