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Case ReportsAbstract
Hidradenomas are rare benign adnexal neoplasms that present in adults as slow-growing, solid or cystic dermal nodules, often mimicking other cutaneous neoplasms. This clinicopathologic correlation case describes a 27-year-old female who presented with a two-month history of a non-tender nodule on the mid-frontal scalp. Examination revealed a 6-mm pink, excoriated nodule with peripheral yellow crust. A 6-mm punch biopsy removing the entire clinical specimen revealed a mid-dermal tumor involving the epidermis, composed of apocrine epithelioid cells with foci of atypia forming nodules with cystic formation, as well as foci of ischemic necrosis. The neoplasm extended to the biopsy base and edges. Tumor cells were positive for CK7 and actin on immunohistochemistry. These findings supported a diagnosis of nodulocystic hidradenoma with foci of atypia. Hidradenomas with apocrine differentiation and atypical features can closely mimic the histopathologic and immunophenotypic profiles of both benign and malignant salivary gland tumors, making it difficult to distinguish whether the lesion represents a benign solitary hidradenoma or a secondary tumor from a primary salivary gland malignancy. Therefore, management includes excision and screening for a primary salivary gland tumor with physical exam and subsequent imaging with ultrasound, computed tomography (CT) with contrast, or magnetic resonance imaging (MRI) based on clinical suspicion. This case highlights the need for clinical awareness of this histopathological overlap and the need for screening for potential underlying salivary gland malignancy in cases of hidradenoma of the head and neck.