K. Krishnan Unni

Aneurysmal bone cyst : a clinicopathologic study of 238 cases

Aneurysmal bone cyst (ABC) is a nonneoplastic expansile bone lesion that mainly affects children and young adults. Primary ABC is relatively rare, with an incidence one half that of giant cell tumor of bone. In 238 patients with ABC studied in the Mayo Clinic files, more than 80% of the lesions were in long bones, flat bones, or the spinal column. Of the lesions initially treated at the Mayo Clinic, 95% were typical ABC; the rest were „solid”︁ variants. Except for the absence of obvious cavernous channels and spaces, there was no significant histologic difference between solid variant and typical ABC. Radio‐graphically, ABC is an eccentric expansile lesion commonly located at the metaphysis of long bones. Computed tomography and magnetic resonance imaging may show multiple internal septations or fluid levels. In the 153 patients treated, 19% had recurrence after curettage (intralesional excision). Recurrence was most common during the first 2 postoperative years.

Malignancies in fibrous dysplasia

Background. Malignancies in fibrous dysplasia are rare. Most cases have been published as single case reports. The role of radiation therapy in the occurrence of sarcom in fibrous dysplasia is still controversial.

Osteoblastoma: Clinicopathologic study of 306 cases

The clinical, radiologic, and pathologic features of 306 osteoblastomas were analyzed. Seventy-five were Mayo Clinic cases and 231 were from consultation files. Males outnumbered females two to one. The age range was 6 months to 75 years (mean age, 20.4 years). The vertebral column including the sacrum was the most frequent site (32%). Pain was the usual complaint and neurologic findings were associated with vertebral tumors. Although most tumors were well circumscribed, cortical expansion and destruction were common radiographic findings (39%), and 12% had features suggestive of malignancy. Large, epithelioid osteoblasts were seen in 24% and were the predominant cellular element in 10%. A distinctive epithelioid multifocal pattern was recognized. Recurrence rates were 16% (Mayo Clinic cases) and 21% (consultation cases). Tumors involving the central neuraxis were associated with greater morbidity and mortality. Aggressive behavior is within the biologic spectrum of osteoblastomas, and histopathology alone does not appear to be a reliable predictor of aggressiveness. The most important differential diagnosis is osteosarcoma.

Primary chondrosarcoma of long bones and limb girdles

Chondrosarcomas are common solid malignant tumors of bone, second in incidence only to osteosarcomas. The biologic evolution of chondrosarcomas is slow, requiring long follow‐up intervals for meaningful survival analysis.

Epithelioid hemangioendothelioma of bone

Epithelioid hemangioendothelioma of bone is a rare tumor of vascular origin. A series of 40 cases from the Mayo Clinic files was studied to define the pathologic features of this disease and to evaluate any histologic or clinical factor influencing outcome. More than 50% of the tumors were multicentric, with a predilection for bones of a particular anatomical area. In this series, patients with multifocal tumors did not have a better prognosis than those with unicentric disease. We could not predict the outcome of cases on the basis of the histologic features. Visceral involvement was the most important criterion in predicting prognosis. Resection is still the primary treatment for these tumors. Radiotherapy may be useful for surgically inaccessible tumors. Too few patients have received adjuvant chemotherapy to evaluate its usefulness in this setting.

Chondromyxoid fibroma of bone: A clinicopathologic review of 278 cases

In a study of the clinical, radiographic, and pathological features of chondromyxoid fibroma, the tumor was slightly more common in men, usually in the second decade of life. Almost half of the tumors involved the long bones, although the ilium and the small bones were also common sites. Roentgenograms showed a sharply marginated, lobulated, lucent defect in the metaphysis. The tumor involved the medullary bone in an eccentric fashion, and the cortex was thinned and expanded. Periosteal reaction and soft tissue extension were uncommon. Mineralization was identified in 13% of the lesions. Histologically, the tumors were almost always arranged in lobules, which were prominent (macrolobular) or somewhat indistinct (microlobular). The tumor cells were spindle-shaped or stellate and arranged in a myxoid matrix. Calcification was seen in more than one third of the cases but was rarely prominent. Hyaline cartilage and chondroblastoma-like areas were not uncommon. Approximately 18% of tumors showed bizarre nuclei. Permeation of bony trabeculae was uncommon. Treatment was conservative surgical removal; approximately one fourth of the patients had recurrence.

Malignant giant cell tumor of the tendon sheaths and joints (malignant pigmented villonodular synovitis)

Malignant pigmented villonodular synovitis (PVNS) is a rare lesion whose existence may be debatable. We studied eight cases that we consider to be examples of malignant PVNS. The three male and five female patients were aged 12 to 79 years. The knee was involved in three cases; the ankle in two; and the cheek, dorsum of the foot, and thigh in one each. Four patients had swelling for 6 months to 17 years before presentation. Three cases of malignant PVNS were secondary, arising in patients in whom PVNS had been documented previously, and five cases were primary, with histologic features similar to those of the secondary ones. Important histologic features of malignancy were (a) a nodular, solid infiltrative pattern of the lesion; (b) large, plump, round or oval cells with deep eosino philic cytoplasm and indistinct borders; (c) large nuclei with prominent nucleoli; and (d) necrotic areas. Atypical mitoses were occasionally seen. Four patients died with pulmonary metastasis (two also had metastasis to inguinal lymph nodes). Four patients are alive from 3 1/2 to 5 years after the last surgical treatment. The malignant nature of this lesion, the histologic architecture similar to that of PVNS, and the fibrohistiocytic appearance of the cells suggest that malignant PVNS is an entity.

Chondrosarcoma of the Pelvis: A Review of Sixty-four Cases

Background: Treatment of pelvic chondrosarcoma is a difficult problem for the musculoskeletal oncologist. Poor rates of survival and high rates of local recurrence after surgical treatment have been reported in previous studies. The present study was designed to review the long-term oncologic and functional outcomes of surgical management in a large series of patients with pelvic chondrosarcoma who were treated at a single institution. Methods: The cases of sixty-four patients with localized pelvic chondrosarcoma that had been surgically treated between 1975 and 1996 were reviewed retrospectively. The study was limited to patients who had received no previous treatment for chondrosarcoma. There were forty-one male and twenty-three female patients who had a mean age of forty-seven years (range, fifteen to eighty-eight years). The patients were followed for a minimum of three years or until death. The median duration of follow-up of the living patients was 140 months (range, thirty-nine to 295 months). Results: Thirty-three of the sixty-four patients were first seen with grade-1 chondrosarcoma; twenty-three, with grade-2; one, with grade-3; and seven, with grade-4 (dedifferentiated chondrosarcoma). Thirteen patients had a hemipelvectomy to achieve local tumor control, whereas fifty-one patients underwent a limb-salvage procedure. Twelve patients (19%) had local recurrence, and eleven (17%) had distant metastases. At the time of the final follow-up, forty-four patients (69%) were alive without evidence of disease, thirteen (20%) had died of the disease, six (9%) had died of unrelated causes, and one (2%) was alive with disease. Less than a wide surgical margin correlated with local recurrence (p = 0.014). High-grade tumors correlated with poor overall survival (p < 0.001). All patients who had a limb-salvage procedure were able to walk at the time of the final follow-up, and they had a mean functional score of 77%, according to the system of the Musculoskeletal Tumor Society. Conclusions: Aggressive surgical resection of pelvic chondrosarcoma results in long-term survival of the majority of patients. There is a high correlation between tumor grade and overall or disease-free survival.

Low-grade intraosseous osteosarcoma.

A study of 80 well‐differentiated osteosarcomas, 16 from the Mayo Clinic files and 64 from our consultation files, revealed that males and females were about equally affected, most of the patients were young adults, and skeletal distribution was similar to the distribution seen in conventional osteosarcoma. Radiographs generally showed poor margination, suggestive of malignancy. Histologically, the tumors were composed of spindle cells with only minimal atypia. Some tumors had bone spicules similar to those seen in fibrous dysplasia. An invasive growth pattern was the most helpful feature in differentiating low‐grade osteosarcoma from fibrous dysplasia. Initial treatment was highly variable. Local excision was almost always associated with recurrence. Wide excision was almost never followed by recurrence. The recurrent tumor was a high‐grade, conventional osteosarcoma in 15% of the patients, and this was associated with a poor prognosis. Wide excision seems to be the treatment of choice for this very rare variant of osteosarcoma.

Secondary chondrosarcoma in osteochondroma: report of 107 patients.

Secondary chondrosarcomas are rare; recognition and diagnosis are difficult. Slow growth and late recurrence require long-term followup to understand the clinical course. In the current study, 107 patients had secondary chondrosarcoma arising in a solitary osteochondroma (61 patients) or multiple exostoses (46 patients). All histologic slides were reviewed without knowledge of the outcome, and radiologic studies were available for review in 71 cases. Patients with secondary chondrosarcoma were one to two decades younger than those with primary chondrosarcoma. Male preponderance and a predilection for flat bones were observed. The radiologic signs of sarcomatous degeneration included irregularity of the margin, inhomogeneous mineralization, and an associated soft tissue mass. The tumors generally were well-differentiated. Only 10 tumors were classified as Grade 2. Five-year and 10-year local recurrence rates were 15.9% and 17.5%, respectively, and 5- and 10-year mortality rates were 1.6% and 4.8% for patients having initial treatment at the authors’ institution. Metastasis developed in five patients: in the lung in four patients and in the groin region in one patient. Most patients who died of tumor died of local recurrence. Wide excision had the lowest local recurrence rate. With successful surgical treatment, patients may have long-term disease-free survival.