Primary Cutaneous Adenoid Cystic Carcinoma: A Misdiagnosed Tumor.

Primary cutaneous adenoid cystic carcinoma (PCACC) is a rare, slow-growing adnexal skin tumor with about 250 documented cases. We present a case involving a 66-year-old woman who was treated with ovulation inductors 30 years ago and underwent surgeries for meningioma 20 years ago and invasive galactophoric adenocarcinoma of the left breast 12 years ago. She presented with a gradually enlarging, solid, skin-colored tumor on her scalp, located along an old surgical scar initially diagnosed as a keloid by her surgeon. Clinical and dermoscopic evaluations suggested basal cell carcinoma or a metastatic tumor. Confocal microscopy showed deep infiltration without specific diagnostic clues. However, histopathological examination, immunohistochemistry, and comprehensive investigations confirmed the diagnosis of PCACC. A wide local excision was performed, with no recurrence noted during the two-year follow-up. This case highlights the challenges of diagnosing PCACC through clinical, dermoscopic, and confocal methods. Histological analysis remains essential, particularly to distinguish it from metastatic lesions, emphasizing the need for a thorough diagnostic approach in such cases.