Lipoma arborescens is a rare intra-articular lesion, characterised by diffuse replacement of the subsynovial tissue by mature fat cells, producing prominent villous transformation of the synovium. The aetiology of this benign condition is unknown. We describe six cases involving the knee, discussing the symptoms, diagnosis and treatment.

Resection of primary pulmonary sarcomas can produce an acceptable survival rate if the resection is complete. Cardiopulmonary bypass can be a useful adjunct when tumors involve a resectable area of the heart or great vessels.

Sarcoma developing in association with a metallic orthopaedic prosthesis or hardware is an uncommon, but well recognized complication. We review 12 cases of sarcomas arising in bone or soft tissue at the site of orthopaedic hardware or a prosthetic joint. Nine patients were male, and three were female. Their ages ranged from 18 to 85 (mean 55) years at the time of diagnosis of the malignancy. Five patients had undergone hip arthroplasty for degenerative joint disease, four had been treated with intramedullary nail placement for fracture, two had staples placed for fixation of osteotomy, and one had hardware placed for fracture fixation followed years later by a hip arthroplasty. The time interval between the placement of hardware and diagnosis of sarcoma was known in 11 cases and ranged from 2.5 to 33 (mean 11) years. The patients presented with pain, swelling, or loosening of hardware and were found to have a destructive bone or soft tissue mass on radiography. Two sarcomas were located primarily in the soft tissue and 10 in bone. Seven patients developed osteosarcoma, four malignant fibrous histiocytoma, and one a malignant peripheral nerve sheath tumor. All sarcomas were high grade. Three patients had metastatic disease at the time of diagnosis. Follow-up was available on eight patients: five patients died of disease 2 months to 8 years (mean 26 months) after diagnosis; two patients died without evidence of disease 7 and 30 months after diagnosis; and one patient is alive and free of disease 8 years after diagnosis. Sarcomas that occur adjacent to orthopaedic prostheses or hardware are of varied types, but are usually osteosarcoma or malignant fibrous histiocytoma. They behave aggressively and frequently metastasize. Clinically, they should be distinguished from non-neoplastic reactions associated with implants, such as infection and a reaction to prosthetic wear debris.

Objective: Mandibular invasion by oral squamous cell carcinoma may progress by either an infiltrative or an erosive histological pattern. The infiltrative pattern is marked by nests and cords of tumor cells along an irregular tumor front, and the erosive pattern exhibits a broad, pushing tumor front. The objectives of this study were 1) to define the characteristics associated with each histological pattern of mandibular invasion, 2) to assess the relationship between pattern of invasion and clinical outcome as measured by death with disease and disease presence at last follow-up, and 3) to determine whether the cell cycle markers cyclin Dl and Ki-67 are associated with the histological pattern of invasion or are predictive of outcome. Study Design: Retrospective study of 68 patients with mandibular invasion by oral cavity squamous cell carcinoma treated by mandibulectomy. Methods: The clinical records, pathology reports, and original H&E-stained slides were reviewed for each patient. lmmunohistochemical staining of cyclin Dl and Ki-67 was performed on slides cut from the paraffin blocks of these patients' specimens. Results: The parameters found to be significantly associated with the infiltrative pattern of mandibular invasion included higher tumor grade, medullary space invasion, positive bone or soft tissue margins, history of previously failed treatment, and postoperative tumor recurrence. The infiltrative pattern had a positive bone margin rate of 47.6% and a primary site recurrence rate of 52.6%. In contrast, the erosive pattern had a positive hone margin rate of 4.9o/ c and a primary site recurrence rate of 16.7%. The infiltrative pattern of invasion gave a fourfold increased risk of death with disease and disease presence at last follow-up in univariate and multivariate analyses when compared with the erosive pattern of invasion. The 3-year disease-free survival was 30% for the infiltrative patPresented at the 17th European Congress of Pathology, Barcelona, Spai n, September 18-23 , 1999.From the Department of Otolaryngology (R.J.w., M.A.V.), Massachusetts Eye and Ea r Infirmary; the Department of P athology (S.B.K.),