Case study: Solitary plasmacytoma of the scapula

A 28-year-old female presented to her GP following 12 months of shoulder discomfort and restricted movement. After a poor response to physiotherapy, she was referred to her local shoulder specialist

CT and MRI scans were obtained (Figure 1), which revealed a mass lesion in the right scapula. The patient was then referred to the Oxford Sarcoma Service at the Nuffield Orthopaedic Centre. She was clinically reassessed and screening blood tests were performed.

A trace of Bence-Jones proteins (free kappa light chains) was found in the urine, along with increased serum free light chains, but no paraprotein. Ultrasound-guided biopsy of the scapula revealed a solid proliferation of plasma and plasmacytoid cells. Immunohistochemical staining was consistent with myeloma or plasmacytoma. A bone marrow biopsy showed no plasma cell infiltration. In conjunction with staging CT and PET scans, the final diagnosis was established as a solitary plasmacytoma.

The patient was referred to a haematological oncologist and treated with radiotherapy, receiving 45Gy in 25 fractions over five weeks. Following this course of radiotherapy, a repeat MRI scan demonstrated the unexpected finding of an increase in tumour size by more than 20 per cent (Figure 2), associated with a worsening of pain and stiffness.

To ensure that the diagnosis of plasmacytoma was correct, an open biopsy was undertaken. This confirmed the diagnosis of plasmacytoma, with a low proliferation fraction of 10 per cent. This may have accounted for the poor response to radiotherapy. Similarly, chemotherapy was unlikely to be of benefit, so a radical curative resection was planned.

Surgical treatment
A wide excision of the scapula was performed, including the previous biopsy tracts. The muscular portions of supraspinatus, infraspinatus and subscapularis had to be sacrificed, owing to invasion. It was possible to preserve the distal tendinous portions of these rotator cuff muscles.

An osteotomy was made through the scapula, preserving the uninvolved medial and inferior attachments, maintaining a wide margin. A capsulectomy at the level of the humeral head and anterior dissection to release the coracoid process permitted removal of the segment containing the tumour.

Reconstruction of the excised portion of the scapula was facilitated by a custom-made cobalt-chrome endoprosthesis, which included a polished glenoid joint replacement. The tendinous portion of the rotator cuff was reattached with sutures to a prosthetic mesh, with the mesh cut and sutured around the neck of the endoprosthesis (Figure 3); this polyethylene terephthalate mesh was tubular in shape. Direct closure of the wound was possible and a bipolar sealer aided haemostasis.

The postoperative period was unremarkable and the patient returned home after six days. The use of meticulous haemostasis techniques helped to prevent haematoma/seroma formation, which can help to ensure early discharge from hospital.

A programme of slow rehabilitation was provided, with immobilisation of the arm in a sling for 12 weeks, followed by a graded progression in the range of movement. Passive movements were started immediately following surgery, while active movements were commenced at the six-week mark. An acceptable cosmetic result has been obtained and there has been no neurovascular deficit (Figure 4).

A range of active flexion to 100 degrees and abduction to 90 degrees has been possible, allowing the patient to return to full-time work. Her Musculoskeletal Tumour Society rating scale score was 94.3. Monitoring with repeat serum light chain detection and PET scanning has shown no sign of recurrence at one year post surgery.

Discussion
Shoulder pain is common and accounts for nearly 1 per cent of adult presentations to primary care. Management and red flag symptoms have been well reported.1 This case study emphasises the importance of regular follow-up and an awareness of the rarer causes of shoulder pain. In one study of 140 patients referred after failing with conservative measures, three were found to have a primary chest wall neoplasm.2

Solitary bone plasmacytoma is rare, however, accounting for only 5 per cent of all plasma cell disorders. Males are affected twice as commonly as females and the median age at diagnosis is 55 years.3 It may occur in any bone, but preferentially involves the axial skeleton. The spine is the most common site of occurrence, but scapula, clavicle and rib lesions together account for up to 20 per cent of cases.4 Pain is the most common symptom, directly related to bone destruction.

The key differential diagnosis is myeloma, where the same histological process occurs, but at multiple sites throughout the bone marrow. Current diagnostic criteria for plasmacytoma require a single focus, bone marrow infiltration of less than 5 per cent of nucleated cells and the absence of systemic derangement, such as anaemia, renal impairment and hypercalcaemia.5 Serum electrophoresis will demonstrate a monoclonal protein in up to three-quarters of patients, but at lower levels than in myeloma.

First-line treatment involves radiotherapy, usually 40Gy to spinal lesions and 45Gy elsewhere, with a local control rate of about 90 per cent.6 Chemotherapy is only considered after failing radiotherapy, and surgery is typically reserved only for cases involving structural instability or neurological impairment. Median survival is 10 years, with progression to multiple myeloma in half of patients.7

In this case, the radio-insensitivity of the tumour led to the need for radical surgery. The primary aim of surgery was to remove the entire tumour with clear margins. The secondary aims were to provide the patient with satisfactory cosmetic and functional results. Preoperatively, it was explained to the patient that there was the option of using either a latissimus dorsi reconstruction or a scapular prosthesis for reconstructing the scapular defect. In her case, if the rotator cuff muscles could not be preserved because of tumour invasion, plastic surgical techniques would be necessary for glenohumeral stability, but at the expense of function.

Although there is not an abundance of evidence in the literature on this topic, a recent retrospective study has suggested that scapular endoprostheses may offer better functional results than humeral suspension.8

Excellent functional results have been obtained by subtotal scapulectomy with the preservation of the glenohumeral joint,9 but in this case, removal of the glenohumeral joint was essential to achieve a complete oncological resection. Following detailed discussions, the patient chose a scapular prosthesis, because cosmesis and function were important to her. Her recovery to date has been standard with no complications--an excellent oncological outcome and a very satisfactory functional result.

Mr Benjamin JF Dean is an ST2 surgery, Dr Colin Chu is an F2 trainee and Mr David Noyes is a specialist registrar, orthopaedics, at Oxford Deanery. Mr Duncan Whitwell is consultant orthopaedic surgeon (hip/knee and tumour) at the Nuffield Orthopaedic Centre NHS Trust. Competing interests: None declared.

References
1. Mitchell C, Adebajo A, Hay E, Carr A. Shoulder pain: diagnosis and management in primary care. BMJ 2005;331:1124-8.
2. Demaziere A, Wiley AM. Primary chest wall tumor appearing as frozen shoulder. J Rheumatol 1991;18:911-14.
3. Hu K, Yahalom J. Radiotherapy in the management of plasma cell tumors. Oncology 2000;14:101-8, 111-15.
4. Burt M, Karpeh M, Ukoha O et al. Medical tumors of the chest wall. Solitary plasmacytoma and Ewing's sarcoma. J Thorac Cardiovasc Surg 1993;105:89-96.
5. Dimopoulos MA, Kiamouris C, Moulopoulos LA. Solitary plasmacytoma of bone and extramedullary plasmacytoma. Hematol Oncol Clin North Am 1999;13:1249-57.
6. Jyothirmayi R, Gangadharan VP, Nair MK, Rajan B. Radiotherapy in the treatment of solitary plasmacytoma. Br J Radiol 1997;70:511-16.
7. Kyle RA. Monoclonal gammopathy of undetermined significance and solitary plasmacytoma. Implications for progression to overt multiple myeloma. Hematol Oncol Clin North Am 1997;11:71-87.
8. Pritsch T, Bickels J, Wu CC et al. Is scapular endoprosthesis functionally superior to humeral suspension? Clin Orthop Relat Res 2007;456:188-95.
9. Gibbons CL, Bell RS, Wunder JS et al. Function after subtotal scapulectomy for neoplasm of bone and soft tissue. J Bone Joint Surg Br 1998;80:38-42.

1. Mitchell C, Adebajo A, Hay E, Carr A. Shoulder pain: diagnosis and management in primary care. 2005;331:1124-8.2. Demaziere A, Wiley AM. Primary chest wall tumor appearing as frozen shoulder. 1991;18:911-14.3. Hu K, Yahalom J. Radiotherapy in the management of plasma cell tumors. 2000;14:101-8, 111-15.4. Burt M, Karpeh M, Ukoha O . Medical tumors of the chest wall. Solitary plasmacytoma and Ewing's sarcoma. 1993;105:89-96.5. Dimopoulos MA, Kiamouris C, Moulopoulos LA. Solitary plasmacytoma of bone and extramedullary plasmacytoma. 1999;13:1249-57.6. Jyothirmayi R, Gangadharan VP, Nair MK, Rajan B. Radiotherapy in the treatment of solitary plasmacytoma. 1997;70:511-16.7. Kyle RA. Monoclonal gammopathy of undetermined significance and solitary plasmacytoma. Implications for progression to overt multiple myeloma. 1997;11:71-87.8. Pritsch T, Bickels J, Wu CC Is scapular endoprosthesis functionally superior to humeral suspension? 2007;456:188-95.9. Gibbons CL, Bell RS, Wunder JS . Function after subtotal scapulectomy for neoplasm of bone and soft tissue. 1998;80:38-42.
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