Clear Cell Hidradenoma: A Review of Reported Cases.

Clear cell hidradenoma (CCH) is an extremely rare benign adnexal skin tumor originating from eccrine sweat glands. The purpose of this systematic review is to analyze and demonstrate trends in the location, occurrence, and presentation of CCH as well as its ability to present in advanced disease states. This study identified 460 case reports published from 1979 through 2022 through PubMed searches. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were tightly adhered to. The search keywords were "acrospiroma" and "clear cell hidradenoma." Investigators reviewed the articles and extracted the following information: demographics; medical history and medications; anatomic location and characteristic of the CCH; malignancy; and CCH progression timeline. Of the 460 cases reported, 228 reports with 241 cases of CCH were included in the final analysis. The average age is 54.7 (±21.1) years old, and 54.36% are females. Thirty-five CCH cases were reported to be malignant. The genitourinary system is the most common location for malignant CCH. No statistically significant difference in malignant transformation was observed between genders (p=0.24). Malignant CCH had a mean length 2 cm greater than nonmalignant CCH (p-value=0.023). Cases with reported malignant CCH had CCH for a mean of 2.75 years longer than nonmalignant CCH cases (p-value=0.048). CCH is a rare skin tumor commonly found in genitourinary, facial, and head areas. No significant gender difference was found when looking at malignant CCH. The length of the CCH and the time it grows could be indicators of malignant CCH. Careful histopathologic examination, biopsy, and surgical excision of the tumor are recommended, although there is a chance of recurrence.