Case Report
Australasian Radiology (2007) 51, B119–B121
Fig. 3. I.v. and oral contrast-enhanced axial pelvic CT scan shows bilateral symmetric enlargement of the gluteal muscles (arrows).
Fig. 1. Whole-body bone scan images show increased soft tissue tracer uptake within the gluteal and proximal quadriceps regions bilaterally (open arrows) as well as in the ribs, sacrum and proximal femora (solid arrows).
Fig. 4. A T1-weighted, coronal MRI scan of the pelvis shows solid masses within the gluteal muscles bilaterally (white arrows) and a metastatic deposit within the sacrum (black arrow).
Fig. 2. I.v. and oral contrast-enhanced axial abdominal CT scan shows a mass within the body of the pancreas (arrow).
Fig. 5. A T2-weighted, fat-suppressed, coronal MRI scan of the pelvis shows masses and oedema within the gluteal muscles (white arrows) and a metastatic deposit within the sacrum (black arrow). © 2007 The Authors Journal compilation © 2007 Royal Australian and New Zealand College of Radiologists
B120
MJ AGZARIAN ET AL.
Bilateral symmetric gluteal muscle metastases from pancreatic carcinoma presenting as a myositis MJ Agzarian,1 DN Jones,1 TY Yong2 and P Roberts-Thomson3 1
Division of Medical Imaging, and Departments of 2Medicine and 3Immunology, Allergy and Arthritis, Flinders Medical Centre, Adelaide, South
Australia, Australia
SUMMARY Skeletal muscle metastases from pancreatic carcinoma are exceedingly rare with only a few cases reported in the published work. The case of a 59-year-old man with bilateral, symmetric gluteal muscle metastases from pancreatic carcinoma is presented. This case was clinically challenging as until skeletal muscle biopsy was carried out, the working diagnosis was that of paraneoplastic polymyositis. A brief review of the published work is also presented. Key words: bone scan; computed tomography; pancreatic carcinoma; polymyositis; skeletal muscle metastases.
INTRODUCTION Skeletal muscle is a very unusual site for metastases from any cancer. Skeletal muscle metastases from pancreatic carcinoma are exceedingly rare. Because of the pancreas’ retroperitoneal location, pancreatic carcinomas often remain clinically silent for some time until local invasion or metastatic spread results in symptoms. This present communication describes the case of a 59-year-old man who presented with bilateral buttock and hip pain in association with weight loss and fever. After investigation, it was felt that he had paraneoplastic polymyositis secondary to pancreatic carcinoma. Unexpectedly, gluteal muscle biopsy showed metastatic pancreatic adenocarcinoma.
CASE REPORT A 59-year-old man was referred to Flinders Medical Centre by his general practitioner with a 2-month history of bilateral, progressively worsening buttock and hip pain. This resulted in restricted mobility and difficulty standing from a seated position. The pain was worse at night and interfered with his sleep. His pain was associated with an 11-kg loss of weight and intermittent night sweats. There was no history of abdominal pain. His medical history included type 2 diabetes mellitus, hypercholesterolaemia and two previous right carotid endarterectomies. His only medication was atorvastatin. The patient reported drinking three standard drinks per day. He had a smoking history that was the equivalent of 40 pack years. He did not have a history of pancreatitis. Physical examination showed bilateral tender gluteal muscles that were moderately hard to palpation. Passive movement of the hips was restricted by pain. Mild weakness of hip movement was noted. The remainder of the neurological examination was normal. Examination of the abdomen was unremarkable. No skin lesions of clinical significance were observed. The patient’s general practitioner had organized a wholebody bone scan (99mTc methylene diphosphonate). This showed irregular, abnormal soft tissue tracer accumulation in the gluteal and
proximal quadriceps regions bilaterally, as well as several abnormal foci of skeletal tracer uptake in the ribs, sacrum and proximal femora (Fig. 1). A diagnosis of metastatic bone disease was considered. The cause of the soft tissue uptake was uncertain. The diagnostic possibilities included myositis (possibly as a paraneoplastic process), other inflammatory processes, or less likely, neoplastic infiltration of the gluteal muscles. The abnormal laboratory results on admission were mild leucocytosis (12.3 × 109/L) with predominant neutrophilia (75%), raised erythrocyte sedimentation rate (55 mm/h) and increased alkaline phosphatase (129 IU/L). Creatine phosphokinase (CPK), amylase and ionized calcium were all normal. Chest radiograph was unremarkable. Overall, a metastatic neoplastic process was felt to be the most likely diagnosis, with a paraneoplastic inflammatory myopathy involving the pelvic girdle (despite the normal CPK result). An abdominal ultrasound scan was carried out, which showed a 3.0 cm × 3.5 cm hypoechoic mass in the body of the pancreas with appearances that were highly suspicious of pancreatic carcinoma. A CT scan of the abdomen and pelvis was then carried out. This supported the sonographic suspicion of a pancreatic carcinoma involving the body of the pancreas (Fig. 2). This was subsequently confirmed by fine-needle aspiration. There was also evidence of striking bilateral, symmetric enlargement of the gluteus medius and minimus muscles as well as the rectus femoris muscles (Fig. 3). The symmetric, bilateral nature of the abnormality favoured an inflammatory process, such as paraneoplastic polymyositis, although normal creatine kinase result was noted. Core biopsy of the gluteal muscles showed metastatic adenocarcinoma. An MRI scan of the pelvis showed solid masses in the gluteus medius and minimus muscles bilaterally, with surrounding oedema (Figs 4,5). Metastatic deposits were also noted within the sacrum, bony pelvis and proximal femora (Figs 4,5), confirming the bone scan findings. The patient was discharged from hospital and died shortly afterwards. An autopsy was not carried out.
MJ Agzarian BM BS(Hons); DN Jones BM BS, FRANZCR; TY Yong MB BS; P Roberts-Thomson MB BS, MD, FRACP. Correspondence: Dr Marc J Agzarian, Division of Medical Imaging, Flinders Medical Centre, Flinders Drive, Bedford Park, SA 5042, Australia. Email:
[email protected] Submitted 11 January 2005; accepted 12 February 2006. doi: 10.1111/j.1440-1673.2007.01693.x © 2007 The Authors Journal compilation © 2007 Royal Australian and New Zealand College of Radiologists
MUSCLE METASTASES FROM PANCREATIC CANCER
B121
DISCUSSION
CONCLUSION
Pancreatic carcinoma is the fifth leading cause of death by cancer in Australia after lung, colon, prostate and breast cancers.1 It has one of the highest mortality rates of any cancer with a 5-year survival of less than 5%.2 Largely because of the pancreas’ retroperitoneal location, pancreatic carcinoma generally presents late in its clinical course with constitutional symptoms (weight loss, general malaise, night sweats, anorexia) and pain as a result of local invasion and metastatic spread.2 Skeletal muscle metastases from pancreatic carcinoma are exceedingly rare. The usual sites for metastases are regional lymph nodes, liver, lung, peritoneum, bile ducts, adrenal glands and bones.2 There have been only six reported cases of skeletal muscle metastases from pancreatic carcinoma in the published work.3 The muscles involved were psoas, rectus abdominis, pectoralis major, quadriceps femoris, biceps and gluteus maximus.3 In all of these cases, the involvement was unilateral. Symmetrical, bilateral muscle metastases have not, to our knowledge, been previously reported in the published work. In other case reports of skeletal muscle metastases, the most common primary tumours have been lung carcinoma, thyroid carcinoma, melanoma, lymphoma and leukaemia.4 Pancreatic carcinoma is a particularly unusual tumour to metastasize to the skeletal muscle. Skeletal muscle metastases are intriguing as clinically they are so rare, despite the skeletal muscle comprising approximately 40% of average bodyweight.4,5 Several factors have been proposed to explain this phenomenon, including turbulent blood flow through skeletal muscle, local heat production, lactic acid metabolism and local protease production.3–5 Some autopsy series have suggested a higher incidence of skeletal muscle metastases of up to 16%.5 This may imply that such metastases are either clinically not detectable or that the skeletal muscle metastases have been misdiagnosed. Alternatively, selection bias in such limited autopsy series may have resulted in an estimated incidence much higher than is actually the case. A polymyopathy resembling polymyositis can occur as a paraneoplastic syndrome, as part of the subset of conditions known as neuromyopathic paraneoplastic syndromes.2,6 Other conditions in this group include peripheral neuropathies, cortical cerebellar degeneration and a myasthenia syndrome similar to myasthenia gravis. These neuromyopathic paraneoplastic syndromes are most commonly associated with bronchogenic lung carcinoma.2 They have also been reported to occur with breast carcinoma, gastric carcinoma, hepatocellular carcinoma and oesophageal carcinoma.2 Pancreatic carcinoma is not a primary tumour usually associated with neuromyopathic paraneoplastic syndromes. The symmetrical, bilateral involvement of the gluteal muscles in this case as shown on whole-body bone scan, CT and MRI would certainly, on first thought, favour a systemic process, such as a neuromyopathic paraneoplastic syndrome. This case shows the importance of obtaining a tissue diagnosis through biopsy, particularly when the imaging findings are non-specifically abnormal and/or there are atypical clinical features. There are no large published reports with treatment and outcome data for skeletal muscle metastases from pancreatic carcinoma. In only one case reported in the published work was treatment given.3 This was in the form of local radiotherapy and systemic chemotherapy. The patient died 3 months after treatment, with no significant decrease in the pain from the skeletal muscle metastatic deposits.3
This case provides a reminder that skeletal muscle metastases from pancreatic carcinoma and other malignant tumours do occur and are worthy of consideration in patients with cancer presenting with soft tissue abnormalities and pain.
© 2007 The Authors Journal compilation © 2007 Royal Australian and New Zealand College of Radiologists
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