Abstract
RATIONALE: Breast low-grade adenosquamous carcinoma is an uncommon cancer that has been neglected in genetic and pathophysiological research. Consequently, medical practitioners face challenges in the effective diagnosis and treatment of this condition. PATIENT CONCERNS: We present the case of a 57-year-old Asian female patient who presented with bilateral breast masses on physical examination. Ultrasound and an MRI revealed a highly suspicious malignant mass in her right breast that was completely removed surgically. DIAGNOSES: After pathological analysis, the diagnosis was low-grade adenosquamous carcinoma with local high-grade transformation, and some of the tumor components were estrogen receptor positive. INTERVENTIONS: The patient underwent appropriate postoperative chemotherapy and achieved a favorable outcome. OUTCOMES: During the follow-up period after surgical resection, the patient did not experience any local recurrence or distant metastasis. LESSONS: Owing to the rare combination of estrogen receptor positivity and high-grade progression, this patient also required adjuvant chemotherapy. This enhances the essential foundation for diagnosing and treating this rare disease, and facilitates the implementation of treatment plans.