Malignant Hidradenoma of the Scalp: A Rare Case with Diagnostic Challenges and Immunohistochemical Insights.

Introduction: Hidradenocarcinoma is an extremely rare and aggressive malignant tumor originating from eccrine sweat glands. It typically presents with nonspecific clinical features, which makes early diagnosis challenging. The tumor is known for its potential for recurrence and metastasis, often complicating management.

Case presentation: A 57-year-old male presented with a painless, gradually enlarging swelling on the scalp, which had been present for 2.5 years. Initially suspected to be an infected sebaceous cyst, the lesion was excised. Histopathological analysis revealed malignant hidradenoma, characterized by clear cytoplasm, nuclear pleomorphism, and increased mitotic activity. Immunohistochemical staining showed 22% Ki-67 and 14% p53 expression, confirming malignancy. No metastasis was found.

Conclusion: Malignant hidradenoma is a rare and aggressive cutaneous tumor that can be challenging to diagnose due to its nonspecific presentation. Early recognition and wide surgical excision are essential for better prognosis and to prevent recurrence or metastasis.