Eccrine
hidrocystomas and apocrine
cystadenomas are morphologically related cystic sweat gland
tumors. To elucidate their cellular differentiation we examined by immunohistochemistry the expression of
keratins and of human milk fat
globulin 1 in 12 of each of these
tumors, diagnosed using established conventional histological criteria. All
tumors diagnosed as apocrine
cystadenomas by these criteria were characterized by a
keratin pattern of secretory type. In addition, they expressed human milk fat
globulin 1.
Tumors diagnosed as eccrine
hidrocystomas expressed a
keratin pattern of excretory type. A part of the
tumors with an excretory
keratin pattern expressed human milk fat
globulin, while others did not. Some presumed eccrine
hidrocystomas expressed the very same
antigens as apocrine
cystadenomas. Thus, our study reveals three distinct types of
tumors, in contrast to the conventional distinction of only eccrine
hidrocystomas and apocrine
cystadenomas. Apocrine
cystadenomas differentiate towards the secretory coil of apocrine sweat glands. Presumed eccrine
hidrocystomas may represent cystic
tumors of the eccrine sweat duct, or they may represent cystic
tumors of the apocrine duct. Thus, the name
hidrocystoma should be used without further specification of an eccrine or apocrine nature, unless certainty is reached by immunohistochemical characterization. Also,
hidrocystomas often prove to be histologically misdiagnosed apocrine
cystadenomas because of a flattened
cyst wall secondary to increased intraluminal pressure.