Identification of aneuploidy in recurrent clear cell hidradenoma by DMA image cytometry (ICM‐DNA)

Since malignant clear cell hidradenoma (CCH) is often characterized by only slight and sometimes by absent nuclear anaplasia, even in metastases, definitive differentiation from its benign counterpart by light microscopy may be very difficult. Herein, we report the case of a 72-year-old woman suffering from a CCH on the back, which showed local recurrence following incomplete excision. By light microscopy no unequivocal signs of malignancy were found either in the primary or the recurrent tumor. However, unusual deep extension to the subcutis with some architectural disorder was seen in the latter. Identification of prospective malignancy in such cases of borderline histopathological features is one of the main indications for diagnostic DNA image cytometry (ICM-DNA). Application of this method to enzymatic cell separation specimens of the recurrence detected marked DNA-aneuploidy with a stemline ploidy of 2.60 c and single events up to 6.7 c, whereas a nearly exact diploid DNA-stemline was found in the primary. We suppose from our results that a prospective malignant CCH with aneuploid DNA-stemline has developed out of its DNA-diploid counterpart. The need for total surgical removal of apparently benign clear cell hidradenomas is further stressed by this observation. Criteria for the diagnosis of malignancy in CCH are reviewed.