Scalp mass: an atypical presentation of multiple myeloma
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A 64-year-old male presented with a 6-month history of a gradually enlarging scalp mass. He recently experienced paresthesia in the region but no pain, drainage or redness. Medical and surgical history includes appendectomy, laparoscopic cholecystectomy, cystourethroscopy with stone excision, anxiety and hypercholesterolemia, with no current medications. Physical exam was normal, except for a 4-cm fluctuant, mobile mass over the left parietal bone.

The initial differential included benign causes of scalp masses, such as lipoma, epidermoid cyst, sebaceous cyst, abscess or hematoma. In the office, the patient was consented for mass aspiration. No fluid was obtained, increasing suspicion for a solid mass. Excision was scheduled at the outpatient surgical center.

Under general anesthesia, a linear incision was made over the parietal scalp mass. Upon dissection, soft hemorrhagic tissue was encountered, with a defect extending through the left parietal bone and into the cranial cavity. The cavity was packed with hemostatic materials and the skin was closed. The patient was transferred to the emergency room for imaging and neurosurgery consultation.

Noncontrast head computed tomography (CT) confirmed a left parietal bone lytic lesion. Brain (MRI) confirmed an enhancing mass involving the left lateral scalp and parietal bone extending down to the dura. T1-weighted image noted additional small enhancing lesions of the frontal calvarium. Initial laboratory studies noted hypercalcemia (serum calcium 10.6 mg/dl) and anemia (hemoglobin 11.5 g/dl).

Neurosurgery recommended left parietal craniectomy, scalp mass resection and titanium mesh cranioplasty. Under general anesthesia the previous incision was opened and extended. A hemorrhagic soft tissue mass was noted, extending from the scalp to the dura. The mass was scraped off the dura, resected and noted to have not infiltrated intradurally. A circumferential craniectomy was performed surrounding the lytic defect. Several smaller areas of lytic bone adjacent to the lesion were drilled until normal bone was present at all edges. After achieving hemostasis, a titanium mesh plate was placed and secured. The wound was closed, the patient extubated and transferred to recovery. Scalp, bone and soft tissue specimens were sent to pathology. Postoperative CT head demonstrated mass resection without intracranial hemorrhage or complication.

The excised parietal bone showed patchy, confluent intramedullary sheets of malignant plasma cells with hemorrhage and necrosis, confirming a plasma cell myeloma diagnosis, and in conjunction with other smaller lytic lesions, a multiple myeloma diagnosis.