Solitary plasmacytomas (SPs) represent ≤5% of all plasma cell neoplasms and mostly occur in the spine, pelvis, ribs and pectoral girdle, while rarely occurring in the sternum. The tumors typically appear as osteolytic lesions. In rare cases, SPs can manifest as bony spicules on the surface of the bone. The present study reports the case of a 74 year-old female with an osteolytic tumor localized in the sternum. The tumor displayed extensive bony destruction, with a large quantity of thick straight spicules on the surface of the bone, resembling a sunray in appearance. The imaging, laboratory and pathological examinations of the patient met the diagnostic criteria of SP. The patient was initially treated with radiotherapy at a dose of 45 Gy. Six months later, chemotherapy consisting of vindesine, Adriamycin and dexamethasone was administered. Vindesine and Adriamycin were administered at a dose of 2 and 15 mg/day, respectively on days 1-4 in a 20-day cycle. Dexamethasone was administered at a dose of 20 mg/day on days 1-4, 9-12 and 17-20 in the 20-day cycle. In total, the patient underwent 6 cycles of chemotherapy, with a total duration of 7 months. The patient was followed-up for two years after beginning therapy. At present, the patient is well, without any evidence of progressive disease or multiple myeloma. To the best of our knowledge, this is the first case in the English literature of SP in the sternum, with an unusual sunray periosteal reaction on radiological imaging. The sites of bony spiculation in the lesions that have previously been described in the literature are the mandible, orbit, vertebral body and skull vault. To the best of our knowledge, the current study presents the first case of a SP of the sternum with a unusual spiculated periosteal reaction on radiological imaging to be reported in the English literature.