Multiple cutaneous neuromuscular choristomas. Report of a case and a review of the literature.

We report a case of two neuromuscular choristomas occurring in separate cutaneous locations in a healthy 3-month-old infant. Both lesions had an identical histologic appearance and were composed of mature skeletal muscle cells admixed with nerve fibers. In all previous reports, neuromuscular choristoma has arisen in association with a major nerve, and most lesions have been solitary. The two separate cutaneous choristomas in this case suggest that this lesion may arise from the neuroectodermal-derived Schwann cell.

Nuchal fibrocartilaginous pseudotumor: a distinctive soft-tissue lesion associated with prior neck injury.

Soft-tissue tumors with a predilection to involve the head and neck region include spindle cell lipoma, pleomorphic lipoma, and nuchal fibroma. We have recently studied three patients with distinctive soft-tissue fibrocartilaginous masses in the posterior aspect of the base of the neck, at the junction of the nuchal ligament and the deep cervical fascia. Two of the patients were women (ages 37 and 40) and one a man (age 53). All three had sustained neck injuries in automobile accidents in the past (27 years, 20 years, and 2 months before surgery, respectively). Each patient presented with a soft-tissue nodule overlying the spinous process of one of the lower cervical vertebrae. Two were painful. Computed tomography and magnetic resonance imaging performed in two patients showed focal thickening of the ligamentum nuchae at the C4-5 and C5-6 levels. All three masses were completely excised. They ranged in size from 1.0 to 1.5 cm. The three lesions were histologically identical, and each consisted of a poorly defined, moderately cellular fibrocartilage nodule located within the nuchal ligament at its junction with the deep cervical fascia. Atypia or mitotic activity was not present. The ligamentous tissue adjacent to the mass was irregular and degenerated. None of the masses have recurred in follow-up periods of 3 to 6 months, and all patients are currently asymptomatic. The lesion we describe is a distinctive soft-tissue pseudotumor that occurs in the mid-line of the lower cervical spine within the nuchal ligament. It is likely non-neoplastic and probably develops as a reaction to soft-tissue injury, in an analogous manner to fibrocartilage metaplasia seen in degenerated tendoligamentous structures. We propose the term "nuchal fibrocartilaginous pseudotumor" for these lesions.

Intramuscular myxoma: a clinicopathologic study of 51 cases with emphasis on hypercellular and hypervascular variants.

Intramuscular myxoma (IM) is a benign soft-tissue tumor that presents as a deeply seated mass confined to skeletal muscle. Surgical excision is virtually always curative. Recurrence, even after incomplete resection, is exceptional. Intramuscular myxoma is classically described as hypocellular and hypovascular, and is composed of cytologically bland stellate and bipolar fibroblasts separated by abundant extracellular myxoid matrix. What is underemphasized, however, is that IMs often show areas of increased cellularity and vascularity that can lead to a mistaken diagnosis of sarcoma, especially myxofibrosarcoma, low-grade fibromyxoid sarcoma, and myxoid liposarcoma. In this report, we describe the clinicopathologic features of 51 IMs with special emphasis on those that exhibit these "hypercellular regions." The patients included 35 women and 16 men who ranged in age from 27 to 89 (mean 52) years. The tumors measured from 2 to 15 (average 5.6) cm and all had a gelatinous, lobulated cut surface. Histologically, they all demonstrated classic hypocellular, hypovascular regions. Thirty-eight tumors contained areas of relative increased cellularity that occupied from 10 to 80% of the tumor. These foci had increased numbers of cells, more prominent vascularity, and often increased collagen content. The hypercellular regions were not associated with cytologic atypia of the constituent cells, mitotic activity, or necrosis. Follow-up information was available for 32 patients and ranged from 3 to 108 (average 30) months. No tumor recurred or metastasized. Areas of hypercellularity are common in IMs. Their recognition is important to avoid an erroneous diagnosis of sarcoma.

Subchondral acute inflammation in severe arthritis: a sterile osteomyelitis?

Although arthritis is often associated with synovial inflammation, the osseous changes in inflammatory and degenerative arthritis are principally reactive, and typically lack an acute inflammatory component. We have recently encountered several osteoarticular specimens removed at the time of large joint arthroplasty that have shown a distinctive pattern of subchondral acute inflammation (SCAI) resembling acute bacterial osteomyelitis. These microscopic findings heretofore have not been recognized as a component of the histopathology of arthritis. To determine the frequency of SCAI, we examined slides (mean four per case) from 164 hip arthroplasties performed at one of our institutions in a single year. A total of 10 cases of SCAI, including the 4 original examples (2 humeral head specimens, 2 femoral head specimens) and 6 identified from the slide review are described in this report. Eight patients were female and two were male (ages 54-86 years, mean 70, median 70). All had severe degenerative joint disease, six had rheumatoid arthritis, and three had osteonecrosis. In none was there a clinical or intraoperative suspicion of infection. Cultures of joint fluid or bone were not performed. In all cases, the inflammation was subchondral (within 1.0 cm of the joint surface), and it was frequently associated with subchondral cysts. In osteonecrotic foci, the suppurative inflammation was diffuse within the marrow space, whereas in viable bone it was nodular and vaguely granulomatous. Special stains for organisms were negative. None of the patients was treated with long-term IV antibiotics. There has been no septic loosening of the prostheses at follow-up intervals ranging from 5 to 36 months (mean: 17 months). Our observations, to the best of our knowledge, are novel. Although we cannot definitively exclude bacterial infection as a cause of SCAI, the histologic and clinical features suggest that SCAI likely represents a noninfectious sterile form of inflammation. Subchondral acute inflammation is possibly secondary to synovial fluid insudation into subchondral cancellous bone in the setting of severe osteoarthritis and/or rheumatoid arthritis.

Lipofuscin pigmentation (so-called "melanosis") of the prostate.

Although intraepithelial pigment in the prostate gland has been termed melanosis, the nature of the pigment is not entirely clear, and many pathologists are not aware of its existence. We examined 863 hematoxylin and eosin (H + E) stained slides from 150 surgical specimens of prostate (69 needle biopsies, 66 transurethral resections, 14 radical prostatectomies, and 1 suprapubic prostatectomy) from 149 patients (age range, 47 to 90 years; mean 70 years) in an effort to characterize this pigment. The 1-3 microns in diameter, predominantly subnuclear, yellow-brown to gray-brown granules with a dark blue rim (by H + E) stained positively with Fontana-Masson, periodic acid-Schiff with diastase, Congo red, luxol fast blue, and oil-red-O and exhibited yellow autofluorescence consistent with lipofuscin. H + E stained slides revealed pigment in the benign epithelium in 86 of 150 cases (57%), within stromal macrophages in eight cases, and in atypical epithelium in two cases of high-grade prostatic intraepithelial neoplasia. Ten cases of invasive adenocarcinoma without recognizable pigment in H + E stained sections were stained by the Fontana-Masson technique, and pigment was identified in malignant epithelium in three of these cases. Ultrastructural examination of intraepithelial pigment in KII-fixed tissue from three radical prostatectomy specimens demonstrated the typical appearance of lipofuscin. Although intraepithelial pigment in prostatic biopsy or resection specimens is usually considered characteristic of seminal vesicle epithelium, our study demonstrates that lipofuscin is commonly present in epithelial cells of benign prostatic hyperplasia and less frequently in those of prostatic intraepithelial neoplasia and adenocarcinoma. The recognition of this pigment is important in preventing diagnostic confusion with seminal vesicle epithelium and with melanocytic lesions.

Giant cell tumors of soft tissue: a clinicopathologic study of 18 benign and malignant tumors.

Primary giant cell tumors (GCTs) of soft tissue resembling osseous GCTs are uncommon but distinct entities. Malignant GCTs of soft tissue have been designated giant cell malignant fibrous histiocytomas; however, there is scant data regarding benign GCTs of soft tissue. Eleven benign and seven malignant GCTs of soft tissue were identified from the authors' consultation files and the surgical pathology files of the Vancouver General Hospital and Massachusetts General Hospital. The tumors occurred in adults (eight men, 10 women; age range, 25-89 years; mean age, 54 years) in the extremities (n = 14) and in the trunk, abdomen, and pelvis (n = 4). In each patient the skeleton was normal and there was no history of prior osseous GCT. Tumors ranged in size from 0.8 to 9.0 cm. Eleven occurred in the superficial soft tissue and seven occurred in deep soft tissue. Grossly they were circumscribed and frequently hemorrhagic. Cystic change was present in seven tumors. Nine tumors were partially surrounded by a shell of reactive bone. In all tumors, multinucleated osteoclast-like giant cells were distributed uniformly and evenly among mononuclear cells. The histologically benign GCTs of soft tissue were identical to typical osseous GCTs. The mononuclear cells in these tumors lacked nuclear atypia or pleomorphism, and the mitotic rate within this population was low (mean, three mitoses per 10 high-power fields [HPF]). In the malignant GCTs of soft tissue, the mononuclear cells exhibited anisocytosis, nuclear atypia, pleomorphism, and readily detectable mitoses including atypical forms (mean, 25 mitoses per 10 HPF). None of the benign or malignant tumors exhibited neoplastic bone production. The benign and malignant GCTs of soft tissue demonstrated a similar immunohistochemical staining profile to GCT of bone ( 12 tumors examined), exhibiting strong positive staining for CD68 within multinucleated osteoclastlike cells, and focal staining of mononuclear cells for CD68, Ham 56, and smooth muscle actin. All tumors were treated by surgical resection. Follow-up information is available for 15 patients (range, 0-108 months). No benign tumor has recurred or metastasized. Of the four patients with malignant tumors for whom follow-up information is available, one died of metastatic disease at 13 months and one developed a local recurrence at 84 months but is alive, apparently free of disease after additional excisional surgery. Primary GCTs of soft tissue are distinctive neoplasms that, like osseous GCTs, exhibit a wide clinicopathologic spectrum. These neoplasms should be distinguished from other giant cell-rich soft-tissue tumors with which they may be confused.

Detection of the EWS/WT1 gene fusion by reverse transcriptase-polymerase chain reaction in the diagnosis of intra-abdominal desmoplastic small round cell tumor.

We report two cases of intra-abdominal desmoplastic small round cell tumor with characteristic clinical, histological, immunohistochemical, and ultrastructural features. Fusion of the EWS gene on chromosome 22 and the WT1 gene on chromosome 11, resulting from the chromosomal translocation t(11;22)(p13;q12), was detected by reverse transcriptase polymerase chain reaction (RT-PCR) in both cases. This translocation has been previously reported in this type of tumor using either cytogenetic or molecular biological techniques. Tumor tissue from both cases revealed no chimeric fusion transcripts characteristic of the Ewing sarcoma family of peripheral primitive neuroectodermal tumors or of alveolar rhabdomyosarcoma, two tumors in the differential diagnosis of intra-abdominal desmoplastic small round cell tumor. This report demonstrates the utility of molecular studies as an adjunct in the diagnosis of this rare and aggressive tumor.

Chondroid lipoma, a tumor of white fat cells. A brief report of two cases with ultrastructural analysis.

Chondroid lipoma is a recently described variant of lipoma with unusual morphologic features. Although classified as a fatty neoplasm, its phenotype is uncertain because it has not been determined whether cartilage is a real component or only simulated by light microscopy and whether the adipocytes demonstrate white or brown fat differentiation, issues that can be resolved only by electron microscopy. We present two cases of chondroid lipoma that ultrastructurally showed abundant intracytoplasmic lipid and glycogen and numerous pinocytotic vesicles, characteristic of white adipocytes. These findings support the conclusion that these tumors are composed solely of fat without true cartilage differentiation.

Epithelioid hemangioma of bone. A tumor often mistaken for low-grade angiosarcoma or malignant hemangioendothelioma.

Epithelioid hemangiomas are benign vascular tumors that usually occur in the skin and subcutis. They have been infrequently recognized in bone. Because of their unusual cytologic appearance and growth patterns, they are commonly confused with malignant tumors. We report a series of 12 epithelioid hemangiomas of bone occurring in adult patients, including five males and seven females whose ages at presentation ranged from 24 to 74 years, with a mean of 46 years. Five tumors were associated with involvement of the adjacent soft tissue. A single patient had multifocal bone disease. The most common presenting symptom was localized pain. Treatment of the patients varied widely; however, none of the tumors behaved aggressively. In 11 cases, adequate tissue was available for immunohistochemical analysis, which revealed positive staining for the epithelial markers cytokeratin and epithelial membrane antigen in nine cases. All 11 tumors stained for factor VIII-related antigen and Ulex europeus agglutinin. We believe that many of the vascular tumors of bone that have been reported as low-grade malignant hemangioendotheliomas probably represent examples of epithelioid hemangiomas. We recommend that the criteria for diagnosing vascular tumors of bone conform to those used for morphologically similar tumors that arise in the soft tissues.

Chondroblastoma-like chondroma of soft tissue: an underrecognized variant and its differential diagnosis.

Soft-tissue chondromas are usually composed entirely of mature hyaline cartilage. Infrequently, however, they may exhibit morphologic features that result in diagnostic difficulty. The authors report a series of eight hypercellular soft-tissue chondromas composed of enlarged chondrocytes within a variable amount of chondroid matrix that often demonstrated delicate calcifications and contained numerous osteoclast-like multinucleated giant cells. This histologic appearance closely resembles that of chondroblastoma of bone. However, its extraosseous location, dense cellularity, and poorly formed cartilage can cause confusion with more aggressive chondroid neoplasms of soft tissue. The clinicopathologic features of these chondroblastoma-like chondromas are discussed, emphasizing the characteristics that facilitate their accurate identification.

Hyalinizing spindle cell tumor with giant rosettes: a report of three cases with ultrastructural analysis.

We report the light microscopic, ultrastructural appearance and immunohistochemical staining profile of three distinctive soft-tissue tumors recently designated hyalinizing spindle cell tumor with giant rosettes. The tumors occurred in two men, 41 and 54 years old, and one woman, 62 years old. Two tumors arose in the lower extremities and one in the upper arm. Two tumors were resected and measured 3 and 13.2 cm in greatest diameter; a biopsy only was done of the third tumor. Grossly, the tumors had a tan, pink, or white cut surface. The largest tumor exhibited central cystic change. Microscopically, they all displayed similar features and were composed of fibromyxoid regions, with areas of hyalinization in two tumors and focal ossification in one tumor. Scattered throughout each of the tumors were rosette-like structures in which neoplastic cells were arranged around a central collagenous core. Ultrastructurally, the neoplastic cells demonstrated the features of fibroblasts. In all tumors, there was abundant extracellular collagen fibers and in one there were large aggregates of amorphous extracellular external lamina-like material. The center of the rosette-like structures was composed of banded collagen fibers and the cells at the periphery of the rosettes had ultrastructural features similar to the neoplastic spindle cells located elsewhere in the tumor. Immunohistochemically, the tumor cells stained for vimentin. There was focal staining of the widely distributed spindle cells and cells that formed the rosettes for Leu-7, S-100 protein, and CD34. In one tumor, there was faint diffuse staining of the spindle cells for neuron-specific enolase. One tumor (with the amorphous extracellular material) stained for type IV collagen. There was no staining for desmin, muscle actin, smooth muscle actin, keratin, or epithelial membrane antigen. These results demonstrate that hyalinizing spindle cell tumor with giant rosettes is composed of fibroblasts. We did not demonstrate any ultrastructural or immunohistochemical differences between the spindle cells that comprised the majority of the mass and those that surrounded the rosette-like structures. There was no ultrastructural evidence of neural differentiation to explain the focal S-100 protein and Leu-7 staining of the tumor cells.

Epithelioid angiosarcoma arising in a surgically constructed arteriovenous fistula: a rare complication of chronic immunosuppression in the setting of renal transplantation.

Immunosuppression in the setting of solid organ transplantation is associated with the development of a variety of malignant tumors, most commonly squamous carcinomas and non-Hodgkin's lymphomas. Sarcomas, apart from Kaposi's sarcoma, are relatively infrequent. We recently encountered a 71-year-old man with chronic renal failure, treated by allograft kidney transplantation, who developed a high-grade epithelioid angiosarcoma at the site of a nonfunctioning arteriovenous fistula, previously constructed for hemodialysis. At diagnosis, the patient had numerous satellite nodules of angiosarcoma involving the distal skin, soft tissues, and bones. After a below-elbow amputation, there was a rapid local recurrence at the amputation stump. Currently, the patient is alive with numerous pulmonary metastases, 6 months after amputation. A literature review identified three recently reported identical cases of epithelioid angiosarcoma arising in nonfunctioning arteriovenous fistulae. All three patients had been treated by kidney transplantation for renal failure, suggesting a possible causal association between these events. We performed polymerase chain reaction for human herpes virus 8, the recently recognized herpes virus proposed as a major etiologic agent of Kaposi's sarcoma, and possibly some conventional angiosarcomas, but we failed to identify any viral DNA within the tumor.

Giant cell tumor of tendon sheath is a polyclonal cellular proliferation.

Giant cell tumor of tendon sheath (GCTTS) is a common soft tissue tumor. Immunophenotypical evidence suggests it is of synovial cell origin. There is controversy regarding the underlying nature of this lesion, specifically whether it is a neoplastic or nonneoplastic (ie, reactive or hyperplastic) process. Karyotypic abnormalities have been identified in GCTTS and interpreted as evidence of neoplasia, although the finding of similar karyotypic abnormalities in unequivocally nonneoplastic proliferations raises questions about using such findings to define a neoplasm. In an attempt to resolve this uncertainty, a polymerase chain reaction (PCR)-based assay for methylation of the X-linked human androgen receptor gene (HUMARA) was used to assess whether GCTTS is a clonal or polyclonal proliferation. DNA was isolated from formalin-fixed, paraffin-embedded tissue blocks from eight cases of digital GCTTS in female subjects; two cases of hepatocellular carcinoma (HCC) were used as clonal controls. Seven of eight cases of GCTTS were informative, and each showed a polyclonal proliferation, whereas both cases of HCC were clonal. Our results indicate that GCTTS is a nonneoplastic proliferation, if one accepts that a population of cells forming a tumorous mass must show clonality to be classified as a neoplasm. Our results emphasize that simple karyotypic abnormalities do not define a neoplasm. It remains to be determined whether GCTTS is a reactive or hyperplastic process.

Giant cell tumor of tendon sheath and pigmented villonodular synovitis: immunophenotype suggests a synovial cell origin.

Giant cell tumor of tendon sheath (GCTS) and pigmented villonodular synovitis (PVNS) are common synovial "tumors." Their immunohistochemical profile, however, has not been well characterized, and uncertainty exists regarding their histogenesis and relationship to fibroma of tendon sheath. In an effort to clarify these uncertainties and to better define the immunohistochemical profile of GCTS/PVNS, we examined formalin fixed tissue from 35 specimens of GCTS, 12 specimens of PVNS, and three cases of reactive synovitis using avidin biotin complex (ABC) and streptavidin immunohistochemical methods. Antibodies to vimentin, CD68, HAM56, cytokeratins, EMA, S100, HMB45, leukocyte common antigen, CD34, desmin, and smooth muscle actin were used in the study. The proliferating mononuclear cells and surface synovial cells in GCTS/PVNS and reactive synovitis stained positively for CD68, HAM56, and vimentin only. Multinucleated cells stained for CD68, vimentin, and leukocyte common antigen. All other stains were negative. Our results suggest that GCTS/PVNS are tumors of synovial cell origin, and do not support an association between GCTS and fibroma of tendon sheath.

Solitary fibrous tumor of the periosteum.

We report a solitary fibrous tumor (SFT) of the leg that presented as a pedunculated encapsulated soft tissue mass attached to the periosteum of the posterior tibia. To our knowledge this is the first reported case of an SFT in an extremity. In addition to having the typical gross and microscopic appearance of a usual SFT, this SFT also contained abundant elastic tissue, suggesting an origin from periosteal fibroblasts. This report further extends the anatomic range of the SFT, a neoplasm once thought to be of mesothelial origin but now recognized as a mesenchymal tumor of probable fibroblastic lineage. To date the behavior of the this periosteal SFT has been benign.

Giant cystic arachnoid granulations: a rare cause of lytic skull lesions.

Arachnoid granulations provide the pathway for drainage of cerebrospinal fluid from the subarachnoid space into the dural venous sinus system. They frequently produce small, well-defined indentations on the inner table of the calvarium that are easily recognized on radiographic studies and gross examination of the skull. We report a series of four giant cystic arachnoid granulations presenting as large "destructive" osteolytic lesions that required surgical exploration. The cysts were filled with cerebrospinal fluid and were delineated by a thin fibrous wall that contained peripheral clusters of arachnoid cells. We discuss the pathologic and radiographic differential diagnosis of osteolytic skull lesions and present a hypothesis regarding the formation of giant cystic arachnoid granulations.

Expression of epithelial markers in malignant fibrous histiocytoma of the musculoskeletal system: an immunohistochemical and electron microscopic study.

We performed an immunohistochemical and ultrastructural study on 67 specimens of malignant fibrous histiocytoma (MFH) from 65 patients. Most of the tumors were musculoskeletal in origin and all presented clinically as a primary malignancy. The tumors were high grade and 57 of 67 were the storiform-pleomorphic subtype. Immunohistochemical studies were performed in 34 cases with both fresh-frozen and formalin-fixed tissue; in 33 cases only formalin-fixed tissue was available. The immunohistochemical panel included vimentin, various molecular weight keratins, epithelial membrane antigen (EMA), desmin, alpha-1-antitrypsin, and alpha-1-antichymotrypsin. Seventeen of 67 (25.4%) cases stained with one or more keratin antibodies. The low molecular weight cytokeratins demonstrated the most widespread and intense staining and, using fresh-frozen tissue, increased sensitivity. Epithelial membrane antigen was detected in 20.6% of cases and six of these cases also stained with keratin. The EMA staining was more focal and less intense than the keratin reactivity. The keratin- or EMA-positive cases were not distinguished by their light microscopic or ultrastructural features. Desmin staining was focally present in 16.9% of cases. The vast majority of tumors stained with vimentin and alpha-1-antitrypsin or alpha-1-antichymotrypsin. There was no staining of tumor cells for S-100. Appropriately fixed tissue was available for electron microscopic evaluation in 15 of 23 MFHs that stained with keratin or EMA. Ultrastructurally, all tumors were composed of an admixture of cells that had the features of fibroblasts, myofibroblasts, and histiocytes; no epithelial structures were identified. This study confirms that MFH may express epithelial markers. It emphasizes the importance of using electron microscopy and clinical findings to distinguish keratin or EMA-positive MFH from carcinoma. This distinction is important because of the significant differences in therapy and prognosis.

Extraosseous primary and recurrent giant cell tumors: transforming growth factor-beta1 and -beta2 expression may explain metaplastic bone formation.

Giant cell tumor (GCT) of bone is a locally aggressive neoplasm with a high incidence of recurrence, usually at the site of previous osseous involvement. Primary and recurrent intraosseous lesions typically are lytic and do not show evidence of tumor-associated osteogenesis. Rarely, GCT recurs or is primary within soft tissue, and not infrequently, these extraosseous lesions show metaplastic bone formation that is visible radiographically. The authors report two recurrent and one primary case of extraosseous GCT, all of which exhibited significant deposits of metaplastic bone localized to the periphery of the lesions. In situ hybridization showed messenger RNA (mRNA) for transforming growth factor beta1 (TGF-beta1) and transforming growth factor beta2 (TGF-beta2) in neoplastic stromal cells and osteoclast-like giant cells within the recurrent and primary extraosseous tumors as well as in active osteoblasts on the surfaces of recently formed spicules of metaplastic bone. In situ hybridization also revealed mRNA for TGF-beta1 and TGF-beta2 in primary intraosseous tumors from these cases and from four cases in which neither extraosseous recurrence nor osseous metaplasia was identified. In the microenvironment of the extraosseous soft tissue, production of these osteoinductive growth factors by GCT may have a paracrine effect on mesenchymal progenitor cells, thereby stimulating the osteoblastic differentiation and metaplastic bone formation associated with these lesions.

Pathology of the synovium.

Synovium is specialized mesenchymal tissue that is essential for the appropriate function of the locomotor apparatus. It is the site for a series of pathologic processes that are characteristic, and in some cases specific, to this distinctive tissue. In this article, the normal microscopic anatomy of synovium is briefly reviewed. Synovial proliferative disorders, including pigmented villonodular synovitis, giant cell tumor of tendon sheath, hemosiderotic synovitis, and fatty infiltration of the synovial membrane are discussed. Additionally, the subjects of intrasynovial cartilaginous lesions (primary and secondary synovial chondromatosis) and crystal deposition diseases are reviewed. Finally, the response of synovial tissues to implanted foreign materials that are used in large and small joint arthroplasty are described.

Histiocytic lymphadenitis associated with a large joint prosthesis.

Distinctive microscopic findings in enlarged axillary lymph nodes removed during modified radical mastectomy in a 76-year-old woman with a previous ipsilateral total shoulder joint replacement are described. The sinuses of the lymph nodes were distended by numerous large macrophages that had abundant granular eosinophilic cytoplasm. Periodic acid-Schiff staining was positive, and polarization microscopy revealed birefringent particles of polyethylene. These findings were diagnostic of the reactive lymphadenopathy that is seen uncommonly in lymph nodes draining large joint prostheses.