Solitary plasmacytomas (SPs) are aggressive tumors characterized by the local proliferation of neoplastic monoclonal plasma cells without the systemic features of multiple myeloma [1],[2]. They are divided into two categories based on the affected tissue type: solitary bone plasmacytoma (SBP), found in bone, and extramedullary plasmacytoma (EMP), found in soft tissues. Solitary bone plasmacytoma most commonly presents in the axial skeleton, whereas EMP predominantly appears in the aero-digestive tract of the head and neck [3],[4]. Plasmacytomas involving the soft tissue of the cervical spine are relatively uncommon, and limited data exist on their management [5].

Solitary plasmacytoma is a rare condition with a cumulative incidence of 0.15 per 100,000 individuals. Only 30% of cases present as EMP [6],[7],[8]. Diagnosing EMP involves a tissue biopsy showing an isolated mass of monoclonal plasma cells in the soft tissue, and the absence of hypercalcemia, renal insufficiency, anemia, and bone lesions (CRAB). It is typically detected using positron emission tomography/computed tomography (PET/CT) or CT with contrast and is treated with moderate to high doses of radiotherapy with or without surgical intervention. Adjunctive chemotherapy remains a controversial treatment for SP and is not recommended [8],[9],[10],[11]. Historically, EMP has a significantly higher overall survival and progression-free survival when compared to SBP, and significantly lower rates of transition into multiple myeloma [2],[4].

Here we discuss the case of a 53-year-old male with an extramedullary plasmacytoma presenting as a rapidly growing lateral neck mass.

History

The patient is a 53-year-old male who presented to the Emergency Department of a tertiary academic medical center with a 4-week history of an enlarging left neck mass. The mass was first noticed after the patient sustained a mechanical fall at home and subsequently began to experience an increasingly painful region on the left side of his mouth without any limitation in range of motion. The pain was described as a dull ache, originating from inside of his mouth and around his left temple and jaw, and behind his left ear. The patient endorsed having had a dry cough with intermittent vomiting over the antecedent few months, along with an approximate 30-pound weight loss over a 5-month period. He also noticed increasing fatigue over the same time period but denied any other constitutional symptoms. His past medical history was significant for congestive heart failure, diabetes, hypertension, and hyperlipidemia, and his past surgical history was significant for a previous lumbar spine decompression and fusion. He denied smoking or illicit drug use but admitted to occasional alcohol use. He was admitted to the family medicine service.

Imaging was obtained including a contrast enhanced CT of the head and neck, and a non-contrast CT of the cervical spine. These images revealed a large left-sided soft tissue mass approximately 4 × 3 × 7 cm in dimension extending cephalad from the level of C4 to the base of the skull (Figure 1 and Figure 2). There was considerable erosion of the clivus, the medial aspect of the mastoid process, the occiput, and the C1 and C2 vertebrae (Figure 3 and Figure 4). The mass also extended into the left side of the spinal canal. Neurosurgical consultation was requested.

Examination

On physical exam a 2.5 cm × 3 cm firm, non-tender, non-mobile mass was palpated on the left lateral side of the neck at the angle of the mandible. The mass extended behind the ear. No focal neurologic deficits were noted. A thorough discussion with the patient and his family detailed the extent of the mass, and its’ likely etiology as a tumor of undetermined origin and further oncologic work-up was recommended. Additionally, because of the gradually worsening neck pain, and imaging suggestive of aggressive erosion of the base of the skull and upper cervical vertebrae by tumor, a two-stage surgical procedure was also recommended. The initial procedure described was a posterior cervical decompression, biopsy, and/or resection of the epidural component of the tumor, accompanied by spinal stabilization with instrumentation. The second stage, depending on pathology, would be resection of the soft tissue neck mass by the otolaryngology service. All preoperative labs were unremarkable.

Operation

Spinal stabilization with an occipital to C6 instrumented fusion was performed prior to spinal cord decompression. Under fluoroscopic visualization, 3.5 × 10 mm lateral mass screws were placed bilaterally at C3, C4, C5, and C6 utilizing the Magerl technique. An occipital plate was affixed utilizing two 8 mm screws lateral to the midline and a 12-mm screw in midline (Figure 5 and Figure 6). Bilateral angulating rods were contoured and appropriately placed into the screw and plate heads respectively. Locking set nuts were placed and torqued to their appropriate final torquing tensions. Allograft and bone morphogenic protein (BMP) were utilized to augment the fusion. After occipital-cervical stabilization has been achieved, C1 and C2 posterior cervical laminectomies were performed to decompress the spinal cord. Tumor was noted to be densely adherent to the cervical dura on the left side of the spinal cord. No attempt was made to dissect it from the dura due to the potential risk of spinal cord injury from manipulation, and the risk of a dural tear leading to cerebrospinal fluid leakage. Likewise, no attempt was made to dissect tumor from the walls of the left vertebral artery since the right vertebral artery was noted to be atretic on preoperative imaging thereby rendering the left vertebral artery as the predominant blood supply to the posterior circulation. All tissue that was resected was sent to pathology including bone, muscle, and soft tissue. The patient recovered well in the post-anesthesia care unit and was later transferred to the floor.

Pathological findings

The final surgical pathology revealed CD38+ clonal plasma cells with cytoplasmic Kappa light chain restriction. The tumor was negative for CD19 or CD20 (Figure 7).

Postoperative course

The radiation therapy and medical oncology services were consulted, and adjuvant therapy was outlined. After the surgical wound was appropriately healed, a total of 3000 cGy of radiation in 200 cGy fractions was given to the region of the tumor, however, there was no resultant decrease in tumor size. Chemotherapy with 2.8 mg intravenous (IV) Bortezomib and Revlimid was subsequently initiated. Most recent follow-up at 29 months indicated that the patient’s surgical scar had healed well, and there were no symptoms of head or neck pain or occipito-spinal instability. The left lateral neck mass had decreased in size, and the patient had significant clinical improvement. Unfortunately the patient has since passed from an unrelated cause.

Extramedullary plasmacytomas (EMPs) are a rare form of n-on-Hodgkin’s lymphoma characterized by the local expansion of plasma cells into the soft tissue. These tumors comprise approximately 3% of all plasma cell neoplasms and arise in the aerodigestive tract in over 80% of documented cases in the literature [3],[12]]. Cases of soft tissue cervical masses have not been reported to the authors’ knowledge. The literature shows that EMPs affect males almost twice as much as females, with an average age of 55 years at the time of diagnosis [13]. The EMP is distinguished from other plasma cell tumors by the absence of systemic signs. This excludes the possibility of multiple myeloma, the most common plasma cell neoplasm. Extramedullary plasmacytomas are most definitively differentiated from other plasma cell tumors or lymphomas by a positive CD38 and monoclonal cytoplasmic light chain expression of malignant plasma cells obtained by surgical or needle biopsy, as in our patient [14].

Tumors of the neck which erode the bony cervical spine or invade the spinal canal can have devastating neurologic consequences. Bony collapse, and cord compression can result in significant neurologic compromise. Awareness of the symptoms of presentation: pain, progressive motor and sensory deficits, and myelopathy enhances the ability to make an early diagnosis and intervene surgically before catastrophic neurologic consequences occur [15]. Surgical techniques can vary based on the anatomic location and extent of local destruction caused by the neoplasm. This patient’s soft tissue tumor was sub-totally resected to relieve spinal cord compression and provide tissue for diagnosis. Because of the immense potential for occipital-atlanto-axial instability, stabilization was accomplished with instrumented arthrodesis. Ultimately postoperative adjuvant therapy was also given. At our most recent follow-up, the patient had significant resolution of his pain as well as a decrease in his tumor burden. Extramedullary plasmacytomas are difficult to treat, however, multi-disciplinary management should be the paradigm used to provide optimal outcome.

This case represents the unusual presentation of an extramedullary plasmacytoma to the soft tissues of the neck with subsequent erosion of the base of the skull and upper cervical vertebral spine. A satisfactory therapeutic response was obtained with surgical stabilization followed by adjuvant radiation and chemotherapy.