We performed a clinicopathological analysis of 305 cases of primary cutaneous invasive squamous cell carcinoma (SCC) diagnosed in Tokushima University hospital in the past 25 years. We proposed a new clinicopathological classification of SCC based on epidemiological factors and divided it into nine categories; actinic keratosis type, bowen type, keratoacanthomatous type, cystic type, genital type, cicatricial type, radiodermatitis type, xeroderma pigmentosa type, and miscellaneous type. We examined the clinicopathological characteristics in each category such as favorite locations and prognosis. Among the clinical characteristics of those cases, such as sex ratio and age at the time of the excision, the favorite sites were similar to those in former reports in Japan. The actinic keratosis type is a significant type with little metastasis, but the radiodermatitis type and the genital type showed high metastatic rates. The case that occurred on the face showed little metastasis, but the cases on the lower limbs and genitalia had high metastatic rates. Cases with a tumor thickness of less than 4 mm showed lower metastatic rates than those with a tumor thickness of more than 4 mm. We divided those 25 years into five year segments as investigation periods and examined the numbers of cases, sex ratios, and the frequencies of the actinic keratosis type, the Bowen disease type, and the other types and found that these factors were essentially equal.
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