Hidradenomas are rare benign adnexal neoplasms that encompass a morphological gamut with a range of differentiation. As a consequence, there is a great likelihood of being mistaken for other primary and metastatic tumors. Though conventionally regarded as eccrine, they have been reclassified into eccrine and apocrine types.
This study aims to document the histological spectrum of nodular hidradenomas, with particular reference to categorizing them into eccrine or apocrine tumors.
A total of 15 cases with features of nodular hidradenoma with their age ranging from 18 years to 73 years were studied. Most of the cases were solitary, circumscribed, solid and cystic, dermal, symmetrical, lobulated tumors with a sheet-like and papillary architecture. The cells were chiefly eosinophilic with a regular oval grooved nucleus and a small inconspicuous nucleolus. Clear cells were also seen. Squamous differentiation was an important feature, with most showing a infundibular type of keratinization. Sebaceous differentiation is also common. The stroma varied from hyaline to myxoid. Only 1 case showed poroid differentiation.
This study describes the assortment of histologic characteristics in hidradenomas. Apocrine hidradenomas are more common, contrary to earlier belief that favored an eccrine origin.