Presentation
Slowly enlarging, solitary skin nodule on the scalp
Patient Data
The section shows skin with a dermally-based lesion composed of solid and cystic lobules/nodules of cells separated by thick bands of hyalinised fibrous tissue. The cells form sheets and papillary like structures, where cells are arranged around delicate fibrovascular cores. The cells are cytologically bland and show either clear or finely granular eosinophilic cytoplasm.
20x H&E: Tumour centred within dermis, exhibiting lobulated solid and cystic growth pattern.
20x H&E: Tumour centred within dermis, exhibiting lobulated solid and cystic growth pattern.
40x H&E: Densely hyalinised stroma with nodules / islands of tumour cells.
40x H&E: Papillary growth pattern, with central hyalinised fibrovascular cores.
100x H&E: Cytologically bland clear cells with central papillary cores.
100x H&E: Solid nodule of cytologically bland cells with eosinophilic cytoplasm.
400x H&E: High power view of clear cells.
Case Discussion
Nodular hidradenoma may also be referred to as clear cell hidradenoma (when there is a prominent clear cell component) or eccrine acrospiroma. A lesion with numerous aliases, it has also been referred to as clear cell myoepithelioma, solid-cystic hidradenoma and eccrine sweat gland adenoma of clear cell type.
Nodular hidradenoma is a benign dermal-based skin appendageal neoplasm most commonly seen around axillary and scalp regions. There is no connection with the overlying epidermis.
Lesions display a nodular, lobulated, cystic and solid growth pattern and are composed of an admixture of both eosinophilic and clear cells. Trichilemmal-like keratinisation is common, and focal sebaceous differentiation may also be seen. When clear cells predominate, lesions may be referred to as clear cell hidradenoma.
Tumours usually behave in a benign fashion, but may rarely behave aggressively, and may recur if inadequately excised.
When exhibiting striking clear cell differentiation, the possibility of a metastatic clear cell tumour may need to be considered.
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