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SECTION III: REGULAR AND SPECIAL FEATURES: Orthopaedic • Radiology • Pathology Conference: CME ARTICLE

Ulnar Mass in a 51-Year-Old Woman

Price, Eric W MD*; Lopez, Robert MD; Jaffe, Kenneth A MD; Siegal, Gene P MD, PHD§; Klemm, Katrin MD

Author Information
Clinical Orthopaedics and Related Research: July 2004 - Volume 424 - Issue - p 272-279
doi: 10.1097/01.blo.0000129559.46427.b4

HISTORY AND PHYSICAL EXAMINATION

A 51-year-old, right-hand dominant woman presented with a 9-month history of elbow pain. The pain began after she had lifted a heavy sack and felt her left elbow pop. The pain was located in the posterior elbow and proximal forearm. It initially was severe and resolved over several days. One week later she noticed a knot had developed about the elbow. The knot then increased in size during the next few days and was associated with a chronic ache. Lifting heavy objects aggravated the pain.

The patient’s medical history was significant for hypothyroidism, for which she took Synthroid (Abbott Laboratories, Abbott Park, IL).

Physical examination showed a full range of motion (ROM) of her left elbow. There was a soft tissue prominence about the proximal ulna. There was no bruit. There was no lymphadenopathy, erythema, or evidence of infection. Distal pulses were 2+. Median, ulnar, and radial nerves were intact.

Laboratory study showed the leukocyte count to be low at 3100/mL (normal, 4000–11,000/mL) with a normal differential. Hematocrit, platelet count, coagulation studies, urinalysis, electrolytes, and liver function tests were all normal. The sedimentation rate was 11 mm/hour (normal, 0–20 mm/hour). Serum electrophoresis was normal.

Conventional radiographs and magnetic resonance imaging (MRI) scans of the left elbow were obtained (Figs 1–3). A radiograph of the chest taken in two planes, mammogram, and a Technetium 99 bone scan of the patient’s entire body were obtained. Based on the history, physical findings, and imaging studies, what is the differential diagnosis?

Fig 1.
Fig 1.:
Lateral radiograph of the elbow..
Fig 2.
Fig 2.:
Sagittal T1-weighted MRI of the elbow.
Fig 3.
Fig 3.:
Sagittal T1-weighted MRI of the elbow after gadolinium contrast was administered.

IMAGING INTERPRETATION

The radiograph of the elbow (Fig 1) showed an intramedullary lytic lesion of the proximal ulnar shaft. There was expansile remodeling of the cortex and a narrow zone of transition with the adjacent bone at the proximal and distal margins. Prominent bony trabeculations projected within the lesion, reminiscent of those seen in hemangiomas. However, aggressive features also were observed. The posterior cortex was markedly thinned and had a subtle radiolucency within it, suggesting a pathologic fracture. There was an associated soft tissue mass over the dorsal aspect of the lesion. There also was a subtle periosteal reaction at the site of pathologic fracture.

Magnetic resonance imaging (MRI) scans of the elbow (Figs 2,3) were obtained. Sagittal T1-weighted (TR 750/TE 14) spin echo, axial proton density and T2-weighted (TR 4500/TE 45 and 90) fast spin echo fat suppressed, coronal T2-weighed (TR 4429/TE 96) fast spin echo fat-suppressed, and axial and sagittal T1-weighted postintravenous gadolinium contrast spin echo fat suppressed images were obtained. The 4 × 3 cm intramedullary lesion of the proximal ulna had decreased T1 signal, increased T2 signal, and markedly enhanced with contrast. No fluid-fluid levels were seen. Prominent bony trabeculae were seen in the periphery within the lesion. The anterior and posterior cortices had been destroyed at the level of the insertion of the brachialis muscle with extension of the mass into adjacent soft tissues. A soft tissue mass was identified within the proximal extensor carpi ulnaris muscle and the flexor carpi ulnaris, flexor digitorum superificialis, and flexor digitorum profundus origins. A distended cubitoradial bursa was seen. No joint effusion or involvement of the radius was seen.

A Technetium 99 bone scan showed a marked increase in uptake in the proximal metaphysis of the left ulna and the suggestion of an expansile bone lesion. Mammograms of both breasts showed an area of asymmetric breast tissue seen in the upper outer quadrant of the right breast that was benign in appearance and unchanged from a previous mammogram. Imaging of the chest revealed no evidence of metastasis. A computed tomography (CT) scan of the chest, without contrast, was unremarkable.

DIFFERENTIAL DIAGNOSIS

  • Metastatic carcinoma
  • Aneurysmal bone cyst
  • Round cell neoplasm
  • Desmoplastic fibroma
  • Primary malignant neoplasm

An open biopsy was done. The biopsy revealed the following histologic picture (Fig 4).

Fig 4.
Fig 4.:
Hematoxylin and eosin stained section of the tumor (Magnification, ×200).

After the results of the frozen section, the lesion was resected via an intralesional curettage that was augmented using a high-speed burr and phenol. Polymethylmethacrylate was packed in the cavity and a five-hole, ⅓ tubular plate was used for prophylactic fixation.

Based on the history, physical findings, radiographic studies, and histologic picture, what is the diagnosis and how should this lesion be treated?

Continuation of ORP Conference from page 274.

HISTOLOGY INTERPRETATION

Gross inspection of the submitted tissue showed a tan-gray soft tissue mass. An initial frozen section was interpreted as a benign spindle-cell lesion, not otherwise specified. Permanent histologic sections revealed a population of bland spindle cells in a focally myxoid background. These cells were arranged haphazardly around vascular spaces and produced a prominent antler-like (staghorn) pattern (Fig 4). In addition, the connective tissue elements were dense. Mitotic activity, hemorrhage, and necrosis were not present.

A reticulin stain showed abundant reticulin fibers that focally surrounded the individual lesional cells (Fig 5). A stain for Type IV (basement membrane) collagen highlighted the prominent lesional vasculature and its characteristic antler-like (staghorn) appearance. The lesional cells also were reactive with antibodies directed against CD 34 (Fig 6), Bcl-2 (focal), and S100 protein antigen. No reactivity was seen with antibodies directed against CD3l.

Fig 5.
Fig 5.:
Reticulin stain of the tumor (Magnification, ×200).
Fig 6.
Fig 6.:
Lesional cells stained with antibodies directed against CD34 (Magnification, ×100).

Ultrastructurally, the lesion had features consistent with hemangiopericytoma including a proliferation of the perithelial cells that were relatively undifferentiated with euchromatic nuclei containing focally prominent nucleoli. The cells showed elongated and interdigitating cell processes. Intercellular junctions and dense bodies were not seen. However, the cells had focal pinocytotic vesicles (Fig 7). Intermediate filaments were not seen. The cells were separated by little to moderate amounts of basement membrane material. Rare cells were individually invested in basement membrane.

Fig 7.
Fig 7.:
Ultrastructural studies of the tumor (Magnification, ×36,000).

DIAGNOSIS

Primary hemangiopericytoma of the ulna.

DISCUSSION AND TREATMENT

Hemangiopericytoma is a vascular tumor thought to be derived from the pericytes of Zimmerman that surround capillaries. It is reported most often in soft tissues, whereas primary hemangiopericytoma of bone is rare.12 Stout11 first described the primary osseous hemangiopericytoma in 1956. Since then there have been approximately 60 reports and descriptions in the literature.1,3–7,9,10,12,14,15,17

In a review of 11,087 primary bone tumors examined at the Mayo Clinic, Unni13 found only 13 cases of primary osseous hemangiopericytoma. Previously, the Mayo series had reported seven hemangiopericytomas of 8452 primary bone tumors, comprising 0.08% of primary bone tumors, 0.1% of malignant primary bone tumors, 4.7% of primary vascular bone tumors, and 11% of malignant vascular bone tumors.2

In 1988, Tang et al12 reviewed 41 cases of primary osseous hemangiopericytoma from the literature, plus four of their own. Approximately 15 more cases have been reported since then.1,5,7,10 Of these, the sacroiliac, femur, and temporal bones were involved most commonly. None of the tumors has been multicentric. Patient ages ranged from 12–90 years, with a peak incidence in the fourth and fifth decades of life. There was a slight male predominance.12

The most common presenting complaints of patients with an osseous hemangiopericytoma are pain, mass, or both, with symptoms before diagnosis ranging from weeks to years. Local tenderness of the mass is common. Neurologic deficit has been reported in cases of spinal involvement.12 Hypophosphatemic osteomalacia also has been reported frequently in association with an hemangiopericytoma.1,8,9

Radiographic features of an hemangiopericytoma are nonspecific, and are devoid of distinguishing radiographic features that allow a definitive preoperative diagnosis.12 Osteolytic bone destruction is the most commonly reported radiographic change.12 Hemangiopericytomas may show mild osseous expansion, but periosteal reaction and sclerosis are exceedingly rare. Cortical disruption may be present and is thought to predict a more aggressive tumor.13 The radiographs of this bony lesion showed lytic lesions with expansile remodeling.

The radiologic differential diagnosis is broad in general and may include the more benign appearing tumors and tumor-like conditions; giant cell tumor, aneurysmal bone cyst, chondromyxoid fibroma, and fibrous dysplasia; whereas others are more aggressive raising the specter of metastatic carcinoma, fibrosarcoma, round cell neoplasm, and angiosarcoma.12

In 1978, Yaghmai17 reviewed soft tissue and osseous hemangiopericytomas and reported specific angiographic features. He reported that the hemangiopericytoma was the only vascular tumor with specific angiographic features that were constant regardless of tumor location or clinical behavior; these consisted of radially arranged or spider-like branching vessels surrounding and within the tumor. In the capillary phase, the tumor presented as a dense, well-demarcated, round or oval tumor. Occasionally draining veins were seen in the late arterial phase, indicating arteriovenous shunting.5,l7 Arteriographic evaluation was not used in this patient.

Juan et al5 described the MRI findings of a primary hemangiopericytoma of the tibia. With gadolinium enhancement, the tumor had a radially arranged signal-void tubular appearance found in the central portion with a spoke-wheel appearance. These structures correlated angiographically with the feeding arteries and their small branches.5 Previously there had been four other reports that reviewed the MRI findings of these osseous tumors.5 These did not show consistency regarding signal intensity on T1- or T2-weighted images, nor uniformity regarding homogenous or heterogenous enhancement.

Grossly, the osseous hemangiopericytomas are firm, gray-white, and usually can be seen to extend into the surrounding soft tissues.12 Histologically, osseous hemangiopericytomas recapitulate their soft tissue counterparts, which have been described.4 The histologic patterns may be varied and definitive diagnosis of hemangiopericytoma often requires ancillary studies including immunohistochemistry and electron microscopy because many soft tissue tumors may have a focal hemangiopericytoma-like appearance. The lesions are characterized by a proliferation of round to oval cells that are distributed around irregularly shaped vascular channels lined by one layer of endothelial cells.14 The cells show indistinct cytoplasmic borders and do not exhibit marked pleomorphism.16 The vascular channels frequently are slit-like, being deformed by the cellular proliferation surrounding them. This produces the characteristic staghorn appearance under light microscopy. Necrosis usually is not seen. Reticulin staining shows each tumor cell to be surrounded by a sheath of predominantly Type IV collagen outside the capillary walls.16 The lesional cells are immunoreactive with CD34. This intimate relationship between tumor cells and the vascular spaces ideally is present throughout the tumor.

The primary hemangiopericytoma in this case showed more variability in the histologic patterns with areas resembling the classic hemangiopericytoma and other areas with a more myxoid and focally collagenous background. The tumor showed reactivity with antibodies directed against CD-34 and had the classic pattern of staining with reticulin, but did not have an immunophenotype of mimicking lesions such as desmoplastic fibroma or solitary fibrous tumors.

When difficult to define under light microscopy, electron microscopy is a useful adjunct for diagnosis. Certain features frequently were found when 21 soft tissues and one osseous hemangiopericytomas were examined ultrastructurally by Kahn et al.6 These included a basal lamina or basement membrane-like material surrounding cells, and long interdigitating cell processes, cytoplasmic filaments, and pinocytotic vesicles. Dense body formation indicative of smooth muscle differentiation was present in ⅓ of those cases. These are all features also found in normal pericytes and when observed in tumor cells present strong confirmatory evidence of hemangiopericytoma.

Examination of this lesion emphasized the ultrastructural variability accepted for these lesions. The lesional cells usually were elongated with interdigitating cell processes. There were variable amounts of basement membrane material separating the lesional cells, and some of the cells contained pinocytotic vesicles.

Many pathologists argue that the classic appearance of hemangiopericytoma represents a histologic pattern rather than an actual lesion. Whether one thinks that these are true lesions or a histologic pattern, one is obligated to exclude mimicking lesions including solitary fibrous tumor, osteogenic sarcoma, synovial sarcoma, mesenchymal chondrosarcoma, fibrosarcoma, desmoplastic fibroma, and malignant fibrous histiocytoma. Careful histologic evaluation of an adequate number of sections from these lesions and ancillary studies should allow for differentiation of these lesions.

Although the histologic grading of soft tissue hemangiopericytomas has been shown to be a useful correlate of its prognosis,4 controversy remains over the value of classifying and grading osseous hemangiopericytomas in terms of the their malignant potential because the numbers for review are small. Wold et al,16 using a grading system of benign, intermediate, and malignant based on histologic criteria, found it useful to grade the malignant potential when these tumors are primary in bone.16 Tang et al12 described a histologic grading system for these osseous tumors when they reviewed 45 patients. Grade 1 lesions are hypocellular, containing cells with small, ovoid nuclei set in fairly abundant cytoplasm, without prominent nucleoli, and with zero to one mitosis per 10 high power fields. The staghorn-vessel pattern is a striking and characteristic feature. Grade 2 lesions are more cellular containing moderate-sized, ovoid nuclei showing peppery chromatin, small nucleoli, and two to four mitoses per 10 high power fields. Again, the staghorn vascular pattern usually is prominent. Grade 3 lesions are characterized by more numerous cells with small amounts of cytoplasm and enlarged nuclei containing atypical chromatin patterns, atypical nucleoli, and more than four mitoses per 10 high power fields. The vascular pattern is much less discernible than in the other grades. The lesions in all three grades are rich in reticulin.12

The largest review series (that included patients reported by Wold et al16) using the grading system of Tang et al,12 found high-grade or unequivocally malignant osseous hemangiopericytomas usually were associated with rapid recurrence, metastasis, and the patient dies within 2–8 years, whereas patients with low-grade lesions tended to have a much lower risk of metastasis or recurrence and a higher survival rate.12 According to Tang et al,12 although the 5-year survival rate in their series was 75% and the 10-year survival rate was 44%, the prognosis was unpredictable because late recurrences and distant metastases were common.10 In that series, late recurrences were prone to develop many years later, even after 26 years in one patient.

The primary treatment, therefore, is surgical. The goal of therapy is to provide adequate surgical removal of the lesion either by amputation or en bloc resection. The role of adjuvant therapies, such as radiation alone or in combination with chemotherapy is unclear, but probably should be used in patients with lesions in inoperable locations, high-grade lesions at presentation, or local recurrences.10

In the current case, the treatment was an augmented intralesional resection with fixation of the pathologic fracture. This treatment option was chosen based on the initial frozen section result of a benign spindle-cell neoplasm. Final pathologic diagnosis, however, revealed a low-grade hemangiopericytoma of the ulna. Thereafter, a total dose of 67 Gy adjuvant radiation was given. Followup is now more than 3 years and there is no evidence to date of local recurrence or distant metastases. This patient has had an excellent, pain-free, functional result.

See page 276 for diagnosis and treatment.

References

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