Desmoid Tumor of the Subscapularis Presenting as Isolated Loss of External Rotation of the Shoulder (2004)

Isolated loss of external rotation of the shoulder with the arm at the side is a rare clinical finding in patients presenting with a shoulder problem. Most patients with shoulder stiffness are first seen with a loss of mobility involving at least two planes of motion that usually results from primary or secondary adhesive capsulitis1,2. Soft-tissue tumors of the shoulder girdle are rare3. Among soft-tissue tumors, desmoid tumors are very rare and they most frequently occur in the shoulder girdle and the thigh of adolescents and young adults4. Desmoid tumors are slow-growing benign fibrous neoplasms arising from soft tissue and muscle. They have a notoriously high recurrence rate5,6. Adequate surgical resection can be challenging, and early diagnosis is intuitively beneficial in facilitating surgical management before the tumor has invaded and distorted the regional anatomy. We present the cases of two patients with a desmoid tumor originating in the subscapularis muscle who were first seen with vague progressive shoulder pain and a clinical examination pertinent for only marked limitation of active and passive external rotation of the shoulder with the arm at the side. The patients were informed that data concerning their cases would be submitted for publication. Case Reports CASE 1. A fifty-three-year-old woman who was right-hand dominant and worked as an administrator presented with progressive pain in the left shoulder, including mild night pain, of insidious onset occurring over a two-year period. The pain was described as a dull ache of variable intensity deep within the shoulder. She reported that she had not had any fevers or other systemic symptoms. The only prior treatment was a subacromial injection of lidocaine and corticosteroid, which had been given by her primary care physician, and it had provided no relief. Plain radiographs and a computed tomographic arthrogram that had been obtained by her primary care physician were initially interpreted as normal. The medical history and review of systems were unremarkable, she was taking no medication, and she had no history of smoking. On clinical examination, the skin had no abnormalities. No atrophy or asymmetry was noted in the upper extremities or shoulder girdles. Passive and active external rotation with the arm at the side was 10° for the left shoulder and 80° for the right shoulder. The remainder of the examination demonstrated no discrepancies between the right and left upper extremities, including anterior elevation in the plane of the scapula (170°), abduction (175°), internal rotation (seventh thoracic vertebra), and external rotation with the arm abducted to 90° (95°). The rotator cuff strength was completely intact to manual testing. The findings of the lift-off and bellypress tests and the external rotation lag sign were negative7-9. No tenderness was noted about the shoulder, and no masses were palpable. No signs of instability or abnormality of the biceps or labrum were discovered. Although the computed tomographic arthrogram obtained by the primary care physician was initially interpreted as normal (Fig. 1-A), closer inspection revealed that the subscapularis appeared to be excessively thick in its anteriorposterior diameter. Magnetic resonance imaging of the shoulder was then performed (Fig. 1-B), and it demonstrated a lesion within the subscapularis musculature. Fig. 1-A, Fig. 1-B, Fig. 1-C, Fig. 1-D and Fig. 1-E Case 1. A: The original computed tomographic arthrogram showing an excessively thick subscapularis muscle. The arrows delineate the anterior border of the subscapularis. B: A T1-weighted magnetic resonance imaging scan showing the tumor (asterisk) within the subscapularis. The arrows delineate the anterior border of the subscapularis. C: A magnetic resonance imaging scan made two years after the initial tumor resection confirming the recurrence. The asterisk marks the tumor. D: A photomicrograph made at the time of the second resection showing the histological characteristics of the tumor (hematoxylin and eosin, ×100). E: A computed tomographic arthrogram depicting the partial scapulectomy performed during revision surgery. At another institution, the patient underwent an incisional biopsy that revealed a desmoid tumor. A local resection of the tumor with lengthening and repair of the subscapularis tendon was performed. Histologic evaluation confirmed a desmoid tumor. Following the tumor resection, the patient did well for approximately two years and then she began to have a progressive return of the prior symptoms over a three-month period. At that time, the findings on the clinical examination were nearly identical to those on the initial evaluation (external rotation with the arm at the side was 0°, but the findings were otherwise unremarkable). Magnetic resonance imaging showed a tumor recurrence within the subscapularis muscle in the region in which the tumor had initially occurred (Fig. 1-C). The patient then underwent a wide excision of the tumor, including excision of the superior two-thirds of the subscapularis muscle and a portion of the scapular body adjacent to the tumor. A deltopectoral approach was used, and the scar from the previous skin incision was excised. The conjoined tendon was retracted medially, and a wide Homan-type retractor was placed anterior to the subscapularis muscle hinging on the medial border of the scapula. The mass within the subscapularis was palpated and excised en bloc with a cuff of normal-appearing tissue including a full-thickness resection of the portion of the scapula posterior to the tumor. The representative histological characteristics of the tumor are shown in Figure 1-D. All tissue margins were found to be free of reactive tissue and tumor. At the time of writing, twelve months after the most recent procedure, the patient had no signs of recurrence. On clinical examination, she had persistent weakness on internal rotation (grade 4 of 5) but otherwise had normal shoulder function. The findings of the lift-off and belly-press tests were negative, and the apprehension test, drawer test, and load and shift test demonstrated no signs of glenohumeral instability. The scapular body was partially resected during revision surgery (Fig. 1-E). CASE 2. A thirty-three-year-old homemaker who was righthand dominant was seen because of progressive pain in the left shoulder of insidious onset with loss of shoulder mobility that began three years earlier and included pain at night that routinely interrupted her sleep. The pain was described as a constant dull ache of moderate intensity deep within the shoulder. She reported that she had not had any fevers or other systemic symptoms. Two years earlier, she had undergone open arthrolysis at another institution for what had been diagnosed as adhesive capsulitis. The surgery provided no relief of the symptoms. The medical history was positive for three unremarkable pregnancies. She was taking only oral contraceptive medications. She was not a smoker, and the review of systems was unremarkable. On clinical examination, she had a well-healed deltopectoral scar without warmth, redness, or erythema. No atrophy or asymmetry was noted in the upper extremities or shoulder girdles. Passive and active external rotation with the arm at the side was 30° for the left shoulder and 90° for the right shoulder. The remainder of the examination demonstrated no discrepancies between the right and left upper extremities, including anterior elevation in the plane of the scapula (175°), abduction (175°), internal rotation (fifth thoracic vertebra), and external rotation with the arm abducted 90° (90°). Rotator cuff strength was completely intact to manual testing. The findings of the lift-off and belly-press tests and the external rotation lag sign were negative. No tenderness was noted about the shoulder, and no masses were palpable. No signs of instability or abnormality of the biceps or labrum were discovered. A computed tomographic arthrogram made prior to the initial surgery demonstrated thickening of the subscapularis muscle (Fig. 2-A), and magnetic resonance imaging made at the time of presentation demonstrated a tumor (Fig. 2-B). Fig. 2-A, Fig. 2-B, Fig. 2-C, Fig. 2-D and Fig. 2-E Case 2. A: The original computed tomographic arthrogram showing an excessively thick subscapularis muscle. The arrows delineate the anterior border of the subscapularis. B: A T1-weighted magnetic resonance imaging scan showing the tumor (asterisk). C: A photomicrograph made at the time of the initial resection showing the histological characteristics of the tumor (hematoxylin and eosin, ×40). D: Follow-up radiographs, made two months after the initial resection, showing osteonecrosis of the humeral head presumably caused by the initial tumor resection and cystic changes within the humeral head near the lesser tuberosity that are suggestive of tumor recurrence. E: A radiograph made following the revision resection and reconstruction with a reverse design shoulder prosthesis. The patient then underwent an attempt at a wide excision of the tumor, and intraoperative frozen sections confirmed the diagnosis of a desmoid tumor with the margins reported to be free of tumor (Fig. 2-C). A deltopectoral approach was used, and the scar from the previous skin incision was excised. The conjoined tendon was retracted medially, and a wide Homan-type retractor was placed anterior to the subscapularis muscle, hinging on the medial border of the scapula. The mass within the subscapularis was palpated and excised en bloc with a cuff of normal-appearing tissue including the anterior portion of the scapula posterior to the tumor and the subscapularis tendon laterally. Final histological findings following the procedure, however, demonstrated intralesional resection of the tumor at the lateral margin. Additionally, radiographs made two months after the initial tumor resection revealed osteonecrosis of the humeral head and cystic changes within the humeral head near the lesser tuberosity that were suggestive of tumor recurrence (Fig. 2-D). A repeat wide excision with prosthetic replacement was planned. At the time of the repeat wide resection, intraoperative frozen sections demonstrated that the tumor had invaded the lesser tuberosity of the humerus. Wide excision of the proximal part of the humerus was undertaken with use of the previously described surgical approach. The proximal part of the humerus, including the articular surface and both tuberosities, and the remaining rotator cuff tendons were removed en bloc. Reconstruction of the proximal part of the humerus was performed with a reverse design shoulder replacement (Delta; DePuy, Saint-Priest, France) (Fig. 2-E). Following the repeat resection, all tissue margins were found to be free of reactive tissue and tumor. Ten months after the most recent procedure, the patient had no clinical signs of recurrence and no pain. The range of motion was 80° of active anterior elevation in the plane of the scapula, 135° of passive anterior elevation in the plane of the scapula, 80° of active abduction, 130° of passive abduction, active internal rotation to the sacrum, passive internal rotation to the twelfth thoracic vertebra, 0° of active external rotation with the arm at the side, 70° of passive external rotation with the arm at the side, 0° of active external rotation with the arm abducted 90°, and 90° of passive external rotation with the arm abducted 90°. The findings on the lift-off and belly-press tests and the external rotation lag sign were positive. Discussion The cases of these two patients represent an uncommon presentation of tumors about the shoulder girdle. Although these patients presented with symptoms similar to those seen in association with adhesive capsulitis, i.e., pain and loss of motion, the loss of motion occurred in only one plane (external rotation with the arm at the side) in contrast to a frozen shoulder, which has loss of motion in multiple planes10. Although tumors of the shoulder girdle are rare, they must be considered in the differential diagnosis when one is faced with this uncommon presentation. A desmoid tumor in the shoulder girdle typically presents as a solitary painless, deep, firm mass that ranges between 5 and 10 cm in size. Pain can be spontaneous but is usually produced with palpation or movement of the affected muscle. Other associated symptoms include numbness, hyperesthesia, and weakness5,11. Enzinger and Shiraki reported on a series of thirty cases of desmoid tumors in the shoulder girdle12. All patients reported a firm fixed mass in the shoulder region. The mass had grown in size in all patients, and half of the patients had tenderness or pain over the tumor site. Several patients had evidence of impingement upon the brachial plexus by the infiltrating tumor. Seven patients were reported to have growth manifested in the anterior or posterior walls of the axilla. These tumors infiltrated the pectoralis major or the muscles forming the posterior axillary wall, particularly the subscapularis. Impairment of motion, ranging from stiffness of the affected limb to complete paralysis, was noted in several patients. In contrast to these patients, neither of our patients presented with any perceptible mass, which was perhaps secondary to the deep location of the tumor and the relatively early detection. Additionally, neither patient had positive findings during physical examination of the rotator cuff, including specific examination of the subscapularis with the lift-off and belly-press tests, suggesting that these tests are not diagnostic for tumors located within the subscapularis muscle. In these patients, the only clinical finding suggestive of a tumor involving the subscapularis muscle was that of isolated loss of external rotation with the arm held at the side. The cases of our two patients reinforce the use of magnetic resonance imaging as the imaging modality of choice when a tumor of the shoulder girdle is suspected. Although computed tomographic arthrography is very effective in identifying rotator cuff tears, it did not distinguish between the tumor and the subscapularis muscle in these patients, which caused a delay in the diagnosis13. On the basis of the demographic, clinical, and radiographic findings in these patients, the differential diagnosis includes extra-abdominal desmoid tumor, elastofibroma, and, less likely, soft-tissue sarcoma (synovial cell sarcoma, fibrosarcoma, or malignant fibrous histiocytoma). If left untreated, desmoids may become extremely large. They infiltrate adjacent muscle, extend along fascial planes, engulf blood vessels and nerves, and become attached to and erode bone14. Regional and distant metastases rarely occur. Additionally, the strong likelihood of involvement of local musculature, as occurred in our patients, can result in loss of limb function5,11. At the muscle border, the tumor often extends between the muscle fascicles and replaces the perimysium and epimysium before isolating and engulfing the muscle. The tumors tend to grow between and around muscle fibers and thereby isolate the fibers, which undergo atrophy as a result15. Appropriate treatment should include a wide resection of normal tissue surrounding the lesion because it is not possible to assess the true proliferation of the tumor either clinically or histologically. The rate of recurrence has been reported to be as high as 77% in patients who had not had a wide resection5,14. The cases of our patients demonstrated the propensity of desmoid tumors of the shoulder girdle to recur (Case 1), the aggressive measures that may be necessary to resect these tumors, and the reconstruction that may be required to provide a functional limb postoperatively (Case 2). Despite the fact that the first resection in the latter patient was inadequate, the procedure undoubtedly disrupted enough of the proximal humeral vasculature to cause osteonecrosis, illustrating another potential pitfall in the treatment of desmoid tumors of the shoulder girdle. Attempts at wide resection of tumors involving the subscapularis, particularly those extending into its inferior portion, may disrupt the anterior humeral circumflex artery in a proximal enough location to compromise the arcuate branch of the ascending portion of the anterior humeral circumflex artery as well as the collateral flow16. In summary, when a patient is seen because of isolated loss of external rotation of the shoulder, a tumor involving the subscapularis, although rare, must be suspected. A high index of suspicion that is based on clinical examination combined with early magnetic resonance imaging may lead to earlier detection of these tumors, resulting in a technically easier resection and reconstruction.