Heel hidradenocarcinoma regarded as a corn for 25 years with subsequent multiorgan metastasis: a case report and literature review.

BACKGROUND: Hidradenocarcinoma is a rare malignant cutaneous adnexal tumor with nonspecific clinical features. Heel involvement is uncommon and may be mistaken for a benign hyperkeratotic or pressure-related lesion. CASE PRESENTATION: A 44-year-old woman was referred in 2020 with a non-healing left heel lesion that, according to retrospective history, had been regarded as a corn for approximately 25 years. After ulceration and failure to heal following laser treatment, extended excision was performed. Histopathological examination supported hidradenocarcinoma, and all surgical margins were negative. Approximately 2.5 years later, a left inguinal mass developed. Pathological examination showed a poorly differentiated carcinoma consistent with hidradenocarcinoma, with lymphovascular tumor emboli and findings suspicious for lymph-node metastasis. Estrogen receptor expression was negative, progesterone receptor showed weak positivity in fewer than 1% of tumor cells, and HER2 amplification was not detected by fluorescence in situ hybridization. Nab-paclitaxel plus cisplatin achieved stable disease after four cycles. Subsequent gemcitabine plus capecitabine was accompanied by progression, grade 3 anemia, and grade 2 thrombocytopenia. Skeletal and intracranial metastases were identified in early 2024, after which the patient was lost to follow-up. CONCLUSION: Persistent, enlarging, ulcerated, recurrent, or treatment-resistant acral lesions warrant timely pathological assessment. Complete excision remains central to localized disease, whereas regional staging, radiotherapy, systemic treatment, and molecularly guided therapy should be individualized because supporting evidence remains limited.