Malignant hidradenocarcinoma is a very rare and highly aggressive primary skin neoplasm that arises in the eccrine sweat glands. Diagnosis is typically made with histopathological evaluation after excisional biopsy. Reports of this tumor are scarce in the literature, thus making its characterization and management particularly challenging. A 71-year-old male presented in the clinic with swelling of the left lateral axilla on routine dermatological examination. Clinically, the lesion was suspected to be a capillary hemangioma. Upon surgical excision, the specimen was diagnosed as malignant hidradenocarcinoma based on histological characterization with immunohistochemical staining. Subsequent wide excision with sentinel lymph node biopsy was performed, which came back negative for residual tumor and metastasis. Due to the low incidence of this cancer and the markedly poor prognosis, accurate diagnosis of these tumors is highly important. Wide excisional biopsy and sentinel lymph node biopsy appear to be the most common initial treatment plans based on the available literature. With high rates of recurrence and metastasis, there remains the need to characterize effective adjuvant therapy for the post-operative management of hidradenocarcinoma.