Supplementary Material for: Tubular apocrine adenoma with uncertain malignant findings: report of a case and review of the literature

Introduction: Tubular apocrine adenoma (TAA) is a rare sweat gland tumor, usually presenting as a well-defined, red to brown nodule on the scalp. Generally, TAA is considered as benign tumor; however, it may be difficult to differentiate TAA from metastatic or primary carcinoma.
Case presentation: A woman in her 90s presented with a pale red nodule on her right posterior auricle for 3 years. Histology showed several tubular structures contained two layers in the dermis. These showed decapitation secretion. At the periphery of the lesion, squamoid tumor cells formed nest-like patterns. Some squamoid tumor cells exhibited multinucleation. From the histopathological findings, we diagnosed the tumor as tubular apocrine adenoma with uncertain malignant findings.
Conclusion: TAA is a rare sweat gland neoplasm. Although TAA is generally benign, it can exhibit aggressive features, making thorough pathological evaluation crucial to rule out malignancy.