Utility of high-resolution ultrasound for the diagnosis of dialysis-related amyloidosis

OBJECTIVE

To evaluate the utility of real-time, high-resolution ultrasound of the shoulder in the diagnosis of dialysis-related amyloidosis.

METHODS

We performed a case series study of 2 groups of patients seen at a referral-based clinic in a tertiary care hospital. The shoulders of 13 patients with normal renal function and of 38 patients receiving long-term hemodialysis were studied by real-time, high-resolution ultrasound. All hemodialysis patients were evaluated clinically for the presence of dialysis-related amyloidosis. Surgical specimens of joints were available for all 13 patients with normal renal function and for 17 of the 38 hemodialysis patients. These specimens were evaluated for the presence of beta 2-microglobulin (beta 2m) amyloid by Congo red and immunohistochemical staining.

RESULTS

Two ultrasonographic findings were selectively observed in the dialysis patients with clinical and histologic evidence of beta 2m amyloid in comparison with patients with normal renal function and no evidence of amyloid: rotator cuffs greater than 8 mm in thickness and echogenic pads between muscle groups of the rotator cuff. The presence of at least 1 of these 2 findings corresponded to the presence of clinically and histologically evident beta 2m amyloid with a sensitivity of 79% and a specificity of 100%. When additional patients without surgical specimens for histologic confirmation of amyloidosis were included, the sensitivity of these 2 sonographic findings was 72% and the specificity was 97%.

CONCLUSION

Real-time, high-resolution ultrasound is a relatively sensitive and highly specific noninvasive adjunct to the clinical diagnosis of beta 2m amyloidosis in patients receiving long-term hemodialysis.

Long-term salvageability for patients with locally recurrent soft-tissue sarcomas

Between 1971 and 1988, 39 patients were referred because of local recurrence of soft-tissue sarcomas and data from their patient records were analyzed to determine the parameters governing local recurrence. Mean follow-up was 11.1 years, with a mean time to local recurrence of 22 months. Twenty-one patients had local recurrence only, without metastatic disease. Salvage was provided for 14 (67%) of these patients after reexcision of local recurrence, and all 14 patients remained free of disease (mean follow-up, 112 months). We conclude that (1) excisional biopsy of tumors larger than 3 cm leads to potential contamination of clean tissue planes, limits ability to achieve an adequate margin of resection, and may compromise the definitive excision, and (2) in patients with local recurrence only, there is a high rate of long-term salvage (67% for follow-up of 9.3 years) after radical compartmental excision with or without postoperative radiation therapy.

Radiographic detection of metal-induced synovitis as a complication of arthroplasty of the knee

Radiographs of eighteen patients who had had a diagnosis of metal-induced synovitis subsequent to a knee-replacement arthroplasty were retrospectively reviewed. The presence of a dense line outlining a portion of the capsule or articular surface of the knee joint (the so-called metal-line sign) was noted in association with wear in eleven patients. In the nine patients who had a positive sign and also had specimens available for histological examination, there was dense deposition of metal particles, whereas in the six patients who did not have a metal-line sign and had specimens available for histological examination, five had only a slight amount of metal in the synovial tissue and one, a moderate amount. The presence of the metal-line sign was associated with metal-induced synovitis in eleven of the eighteen patients. The sign should be useful in helping to make this diagnosis preoperatively in many patients.

Extrapleural pneumonectomy, chemotherapy, and radiotherapy in the treatment of diffuse malignant pleural mesothelioma

Malignant pleural mesothelioma has been considered a uniformly fatal disease associated with a median survival of 4 to 18 months. Extrapleural pneumonectomy alone has proved disappointing in the treatment of this disease, as have chemotherapy and radiotherapy. From 1980 to 1990, 31 patients with pleural mesothelioma underwent multimodality therapy that included extrapleural pneumonectomy with resection of the pericardium and diaphragm. The age of the patients was 53.4 +/- 8.6 years; 26 were male. All patients had the pathologic diagnosis reviewed before treatment. At thoracotomy six patients had residual (unresectable) gross disease, and in 23 there was histologic evidence of disease at the resection margin. The perioperative morbidity and mortality rates were 19% and 6%, respectively. The mean length of hospital stay for the 29 patients who survived the operation was 10.9 +/- 3.5 days. Postoperatively 26 patients received cyclophosphamide, doxorubicin, and cis-platinum chemotherapy with or without radiotherapy. The survival rates were 70% at 1 year and 48% at 2 years. Trends toward improved survival in the patients with complete resections approached but did not reach statistical significance. These data suggest that this multimodality protocol can be administered with acceptable morbidity and mortality. Prospective trials are justified to further clarify the role of this approach.

Diagnosis of diffuse malignant mesothelioma: experience of a US/Canadian Mesothelioma Panel

The experience of the US/Canadian Mesothelioma Panel with its first 200 cases is reviewed. The light microscopic diagnosis, histochemical findings, immunohistochemical findings, and electron microscopic features of malignant mesotheliomas are reviewed in the context of differential diagnosis. Reasons for referral of case material to the panel and lessons from follow-up of difficult and controversial cases are reported. Recommendations to general pathologists are made regarding evaluation and review of possible mesotheliomas.

Diagnostic relevance of clonal cytogenetic aberrations in malignant soft-tissue tumors

BACKGROUND

Malignant soft-tissue tumors often present substantial diagnostic challenges. Chromosome aberrations that might be diagnostic have been identified in some types of soft-tissue tumors, but the overall frequency and diagnostic relevance of these aberrations have not been established.

METHODS

We attempted to determine the karyotypes of a series of 62 consecutive, unselected malignant spindle-cell or small round-cell soft-tissue tumors (from 46 adults and 16 children) after direct harvesting of cells or short-term culture. All tumors were examined independently by immunohistochemical staining in addition to routine light-microscopical evaluation, and all but two tumors were examined by electron microscopy.

RESULTS

Metaphases were obtained from 61 of the 62 tumors, and clonal chromosome aberrations were identified in 55 (89 percent). In the six tumors that yielded metaphases but lacked apparent clonal aberrations, the normal metaphases were found to originate from non-neoplastic stromal elements within the tumor specimens. Thus, all tumors in which karyotyping was successful contained clonal chromosome aberrations. Forty of 62 tumors (65 percent) contained clonal chromosome aberrations that either suggested or confirmed a specific diagnosis; in 15 of these tumors (24 percent of all tumors), the aberrations were important in establishing the final diagnosis. Cytogenetic analyses were particularly informative about small round-cell tumors from children: 8 of 14 round-cell tumors contained diagnostically important chromosome aberrations. Using the combined approaches of light and electron microscopy, immunohistochemistry, and cytogenetics, we established an unambiguous diagnosis for 60 of 62 tumors.

CONCLUSIONS

Cytogenetic analyses reveal clonal chromosome aberrations in virtually all malignant soft-tissue tumors. These clonal chromosome aberrations, particularly in small round-cell tumors in children, often have diagnostic relevance.

Cytogenetic evidence of clonality in a case of pigmented villonodular synovitis

Pigmented villonodular synovitis is an uncommon benign lesion that is characterized by diffuse synovial proliferation. Based on animal models, this lesion has been conjectured previously to be reactive in nature. In this report, the authors present the histologic and cytogenetic findings for a pigmented villonodular synovitis that was excised from the right knee of a 47-year-old man. Trisomy 7 was observed in 24 of 75 (35%) metaphases obtained from short-term culture of cells from this tumor. These findings suggest that some cases of pigmented villonodular synovitis represent clonal, neoplastic proliferations.

Melanoma and soft tissue sarcoma in seven patients

Seven patients with both melanoma and sarcoma were seen at the Dana Farber Cancer Institute (Boston, MA) over a 4-year period. Three had additional malignant neoplasms; one of these patients also had the hereditary cutaneous malignant melanoma, dysplastic nevus syndrome. These observations suggest the possibility of a biologic relationship between melanoma and sarcoma, the nature of which remains unknown.

Hypodense eosinophils and interleukin 5 activity in the blood of patients with the eosinophilia-myalgia syndrome

The recent recognition of the eosinophilia-myalgia syndrome (EMS) associated with the ingestion of L-tryptophan prompted an analysis of the peripheral blood eosinophil phenotypes and of the serum eosinophil hematopoietins in this disorder. Five patients with an illness characterized by the abrupt onset of aching skeletal muscles, edema, thickening and induration of the skin, and marked blood eosinophilia associated with L-tryptophan ingestion provided eosinophils, serum, or both, for evaluation. Gradient sedimentation density analysis of the peripheral blood eosinophils from four of these patients revealed that 43 +/- 13% (mean +/- SEM) of the cells had converted to the abnormal (hypodense) sedimenting phenotype. When normodense eosinophils from the reference donors were cultured for 3 days in medium supplemented with increasing concentrations of serum from the patients with EMS, their viability increased in a dose-dependent manner to 45%, which was significantly augmented over the effect of normal serum. This eosinophil viability-sustaining activity was inhibited by 76 +/- 7% (mean +/- SEM; n = 3) by the addition of anti-interleukin 5 (IL-5) but not by neutralizing antibodies monospecific for either granulocyte/macrophage colony-stimulating factor (GM-CSF) or IL-3. IL-5, an eosinophilopoietic factor, converts normodense peripheral blood eosinophils in vitro to a hypodense sedimenting form with extended viability and augmented biologic responses to activating stimuli. Thus, the presence of IL-5 in the sera of patients with EMS may contribute to the development and maintenance of the eosinophilia and may regulate the conversion of the peripheral blood eosinophils to the hypodense phenotype with augmented pathobiologic potential.

ME1. A monoclonal antibody that distinguishes epithelial-type malignant mesothelioma from pulmonary adenocarcinoma and extrapulmonary malignancies

ME1 is a monoclonal antibody reactive in frozen tissue sections with normal mesothelial cells and malignant mesotheliomas. In this immunoperoxidase study, ME1 reacted with all 40 epithelial type malignant mesotheliomas. Fifty percent or more of the mesothelioma cells were stained in all cases and the staining intensity was strong in 32 and moderate in eight. In contrast, all 19 well- and moderately differentiated pulmonary adenocarcinomas were completely negative, and of the total 88 non-mesotheliomatous malignancies studied, staining comparable to the mesotheliomas was seen in only 6 tumors (2 pulmonary adenocarcinomas, 2 adenocarcinomas of the breast, 1 adenocarcinoma of the pancreas, and 1 melanoma), although limited, weaker staining was seen in additional cases. Five of the six strongly to moderately positive nonmesotheliomatous tumors had immunoreactivity for complementary immunoreactants (CEA, Leu-M1, S-100 protein, HMB-45). Our results with ME1, the first monoclonal antibody that recognizes malignant mesothelial cells, provides a basis for using this reagent in the differential diagnosis of tumors of the pleura and peritoneum.

Carboplatin in malignant mesothelioma: a phase II study of the Cancer and Leukemia Group B

Carboplatin (400 mg/m2) was given at 28-day intervals to 41 patients with malignant mesothelioma. In all, 40 patients were eligible and evaluable for response. Partial responses were seen in 2 cases (5%); regression of evaluable disease, in 1 patient (2%); and stable disease, in 19 subjects (48%). A median of two doses of carboplatin per patient resulted in mild toxicity. Leukopenia (less than or equal to 2,000 cells/microliters) and thrombocytopenia (less than 100,000 cells/microliters) were seen in only 6% and 20% of the patients, respectively. Median survival from study entry was estimated at 7.1 months, with a 1-year survival of 25% +/- 7%. Carboplatin given at a dose of 400 mg/m2 at 28-day intervals shows minor activity against malignant mesothelioma.

Rheumatoid aortitis: a rarely recognized but clinically significant entity

Aortitis as a feature of rheumatoid arthritis is considered rare. We have, however, identified 10 patients with aortitis from among 188 consecutive autopsy cases of rheumatoid arthritis. There were 5 men and 5 women with a mean duration of rheumatoid arthritis of 9.6 years. Nine were rheumatoid factor positive and had associated nodules. In addition to standard treatment regimens, 9 patients received corticosteroids. Although involvement of the thoracic aorta was most common, involvement of both the thoracic and abdominal aorta was present in 4 cases. Two patients had aneurysmal dilatation of the thoracic aorta and 1 of the abdominal aorta. Microscopic features of aortitis included necrosis of medial smooth muscle and elastica, with an inflammatory infiltrate comprising primarily lymphocytes and plasma cells. A panmural aortitis was seen in 3 cases. Rheumatoid granulomas were noted in the aortic wall in 5. The diagnosis of aortitis was not made until autopsy in any case. Aortitis was hemodynamically significant in 3 patients. Two had congestive heart failure secondary to thoracic aortitis and aortic valvulitis, and 1 had rupture of an abdominal aortic aneurysm at a site involved by aortitis. Seven patients had rheumatoid vasculitis with a mean of 10 organs involved. Six of these died of complications directly related to vasculitis, including 4 patients with coronary arteritis and associated myocardial infarction. Aortitis can be a feature of severe rheumatoid arthritis and is often associated with rheumatoid vasculitis. Hemodynamic compromise does occur and may be fatal.

Pulmonary metastases in patients with low-grade endometrial stromal sarcoma. Clinicopathologic findings with immunohistochemical characterization

Two cases of low-grade endometrial stromal sarcoma (ESS) presenting as cystic pulmonary metastases are reported. Both lung lesions were initially thought to represent examples of so-called mesenchymal cystic hamartoma. A diligent search of the past medical records in the first case revealed that a primary low-grade ESS of the uterus had been resected 27 years earlier. In the second case, a uterine tumor was seen by computed tomography scan and subsequent pathologic examination of the hysterectomy specimen established the presence of a low-grade ESS. Peritoneal metastases, present in both cases, also presented diagnostic problems until the uterine primaries were recognized. Immunoreactivity for desmin was detected in all primary and metastatic tumor sites examined. We conclude that ESS should be included among the desmin-positive spindle cell sarcomas and that metastatic ESS should be included in the differential diagnosis of "benign" mesenchymal cystic hamartoma of the lung.

Keratin protein immunoreactivity of sarcomatoid and mixed types of diffuse malignant mesothelioma: an immunoperoxidase study of 30 cases

To define the role of keratin protein immunohistochemistry in the pathologic diagnosis of the sarcomatoid type of diffuse malignant mesothelioma (DMM), we examined 30 DMM (16 pure sarcomatoid type and 14 mixed sarcomatoid-epithelial type) by an indirect immunoperoxidase technique using three commercially available antibodies to keratin proteins. The sarcomatoid (spindle-cell) areas of all 30 cases of sarcomatoid DMM were immunoreactive for keratin proteins. In 14 of 16 cases of sarcomatoid DMM, 50% or more of the tumor cells were reactive with one or more antibodies; however, polyclonal bovine muzzle and monoclonal AE1/AE3 antibodies were distinctly superior to polyclonal human callus keratin antibody in the detection of spindle tumor cells. In contrast with the staining patterns observed for DMM, 39 spindle-cell malignancies and tumor-like processes of 10 histogenetic types were unreactive with the three antibodies. Those spindle-cell tumors and reactive mesothelial proliferations that may enter into the differential diagnosis of sarcomatoid DMM are discussed. We conclude that keratin protein immunohistochemistry is a sensitive and highly useful method for the pathologic diagnosis of the sarcomatoid type of DMM and its distinction from other spindle-cell neoplasms.

Involvement of chromosome X in primary cytogenetic change in human neoplasia: nonrandom translocation in synovial sarcoma

A translocation that involves chromosome X (band p11.2) and chromosome 18 (band q11.2) was observed in short-term in vitro cultures of cells from five synovial sarcomas and one malignant fibrous histiocytoma. In four of these tumors, the translocation t(X;18)(p11.2;q11.2) was reciprocal. The two other tumors had complex translocations: t(X;18;21)(p11.2;q11.2;p13) and t(X;15;18)(p11.2;q23;q11.2). A translocation between chromosomes X and 18 was not detected in other histological types of soft tissue sarcoma. The X;18 rearrangement appears to characterize the synovial sarcoma and is the first description of a primary, nonrandom change in the sex chromosome of a human solid tumor.

The distinction of adenocarcinoma from malignant mesothelioma in cell blocks of effusions: the role of routine mucin histochemistry and immunohistochemical assessment of carcinoembryonic antigen, keratin proteins, epithelial membrane antigen, and milk fat globule-derived antigen

The immunohistochemical profile (i.e., carcinoembryonic antigen, keratin proteins, epithelial membrane antigen, human milk fat globule-derived antigen, and mucin) of paraffin-embedded cell blocks of 20 malignant effusions from patients with malignant mesothelioma was compared with that of 39 malignant effusions from patients with metastatic adenocarcinoma to determine whether these markers distinguished between these tumor types. Twenty-three adenocarcinomas (59 per cent) stained for mucin. Immunoreactivity for carcinoembryonic antigen (CEA) was observed in 28 adenocarcinomas (72 per cent). All were immunoreactive for keratin proteins, and 29 adenocarcinomas (74 per cent), including seven that were mucin and CEA negative and exhibited a "peripheral predominant" staining pattern for keratin proteins. By contrast, none of the mesotheliomas stained for mucin or for CEA, and, although all were immunoreactive for keratin proteins, none demonstrated a peripheral predominant pattern of staining. Epithelial membrane antigen and milk fat globule-derived antigen were identified in the majority of both mesotheliomas and adenocarcinomas. Neither staining intensity nor pattern of reactivity of these markers clearly distinguished the tumors. This study of cell blocks of serous effusions suggests that staining for mucin, immunoreactivity for carcinoembryonic antigen, and a peripheral predominant pattern of reactivity for keratin proteins represent highly characteristic markers of adenocarcinomas, which identify the majority of these tumors (38 of 39) and allow their distinction from malignant mesotheliomas.

Doxorubicin chemotherapy in the treatment of soft-tissue sarcoma. Combined results of two randomized trials

In 1978, there were initiated two independent randomized, prospective trials of adjuvant doxorubicin hydrochloride (Adriamycin) following primary therapy for soft-tissue sarcoma. The virtual identity of these two protocols permits their combination for analysis. A total of 75 patients (42 men, 33 women) with soft-tissue sarcoma (stages IIB to IVA) were randomized, after receiving optimal regional therapy, to receive either doxorubicin hydrochloride (450 mg/m2) (37 patients) or observation (38 patients). Follow-up has ranged from 16 to 80 months (median, 49 months). Twenty-five patients (33%) died, and two patients receiving doxorubicin developed cardiotoxicity. No significant differences in local control, metastasis-free survival, disease-free survival, and overall survival were observed for the two treatment arms. Despite temporary prolongation of disease-free survival with doxorubicin in some subgroups, we conclude that there is no advantage to the use of adjuvant doxorubicin in the treatment of soft-tissue sarcoma.

Early peritoneal mesothelioma: a treatable malignancy

37 patients with malignant peritoneal mesothelioma were studied to assess the efficacy of combined therapy. 14 patients presented after 1982. Of 6 patients treated intensively, all remain alive with no evidence of disease by computed tomographic scan at 9-36 months. Of 8 patients treated palliatively, 5 are dead. (5 had stable disease, 1 has progressed despite all treatment, and 2 were not treated.) Survival of the intensively treated group is significantly better than that of other stage I patients in this series. Patients under 40 had a significantly better survival rate than older patients.

Optimal immunoreactivity of keratin proteins in formalin-fixed, paraffin-embedded tissue requires preliminary trypsinization. An immunoperoxidase study of various tumours using polyclonal and monoclonal antibodies

The effect of preliminary trypsinization on the immunoreactivity of keratin proteins in formalin-fixed, paraffin-embedded tissues of a variety of tumors (squamous cell carcinomas, adenocarcinomas, mesotheliomas, and transitional cell carcinomas) was evaluated. Three types of trypsin (Type II and Type IX porcine trypsin and Type III bovine trypsin) and varying concentrations of trypsin were assessed. Immunoreactivity of keratin proteins was determined using rabbit anti-keratin antibodies and monoclonal antibodies (combination of AE1 and AE3) and immunoperoxidase techniques. Preliminary trypsinization was mandatory for optimal immunoreactivity of keratin proteins using either polyclonal or monoclonal antibodies. Excellent results were obtained using Type II porcine trypsin at concentrations of 25 mg/dl for 30-45 min or 50 mg/dl for 20 min, at 37 degrees C. Trypsin treatment with excessive concentrations of enzyme and/or extended incubation times promoted tissue digestion and in some cases, yielded decreased immunoreactivity and altered staining patterns.

Immunohistochemical localization of smooth muscle myosin in normal human tissues

Immunohistochemical localization of smooth muscle myosin, an immunologically distinct contractile protein, was achieved using rabbit anti-human uterine smooth muscle myosin antibodies. In immunodiffusion studies and in cryostat sections, these antibodies were highly specific and reacted with smooth muscle myosin but not with platelet, skeletal muscle, or cardiac muscle myosin. To evaluate comprehensively the structural profile of smooth muscle elements in normal human tissues, an indirect immunoperoxidase technique (peroxidase-antiperoxidase) was applied to a wide variety of specimens. Parallel studies comparing cryostat sections with fixed (10% formalin, B5, Bouin's, or Zenker's solution) paraffin-embedded tissues revealed optimal immunoreactivity, sensitivity, and specificity of staining for smooth muscle myosin using frozen tissues. Strong immunoreactivity was present in muscular tissues such as blood vessels and the muscularis of gastrointestinal and genitourinary tracts. Distinct delineation of smooth muscle elements, including individual smooth muscle cells, and their specific patterns of alignment and organization, were observed, e.g., cells comprising the muscularis mucosae and extending into the lamina propria of the gastrointestinal tract, and myoepithelial cells of skin, exocrine glands, and breast. This method provides excellent morphologic preservation and readily permits unambiguous identification of individual cells containing smooth muscle myosin.

Benign and malignant pleural mesothelioma

Malignant mesotheliomas have assumed an importance in the medical and lay literature out of proportion to their incidence in the American population, chiefly due to the known association of pleural mesothelioma with asbestos exposure. Data from the Connecticut tumor registry suggest that this tumor is increasing in incidence. Based on exposures between 1940 and approximately 1970, when industrial precautions were first instituted, epidemiologists estimate that the number of new cases of mesothelioma will peak sometime in the 1990s and that mesothelioma will thereafter become less common. These models generally assume that asbestos exposures after 1970 will be insignificant. While industrial levels that are legal today will almost certainly prevent the development of severe asbestosis in most workers, unfortunately a threshold of exposure below which there is no risk of mesothelioma has not been documented. Asbestos continues to be used in floor and ceiling tiles, in automobile brake linings, and in a variety of other products. At the present time, construction workers who maintain or remove asbestos constitute one of a number of groups with continued exposure. The diagnosis of a malignant pleural mesothelioma is not difficult provided that the physicians caring for such a patient consider mesothelioma in the differential diagnosis. Patients present with chest pain or shortness of breath, or both, and the initial chest x-ray film most often reveals a large unilateral pleural effusion. The tumor characteristically remains localized until late in its course, and thus extensive workup at the time of diagnosis is seldom required. Generally, a large piece of tissue obtained via an open biopsy is required for adequate histologic diagnosis. Investigational approaches include taking numerous needle biopsies with samples sent for electron microscopy as well as for immunoperoxidase staining for keratin and CEA. The treatment of this disease remains unsatisfactory. Occasional patients have remained disease-free for periods in excess of 5 years after intensive treatment, however. The conclusion that mesothelioma is untreatable is clearly untenable since palliation and a response rate of 30 per cent to various chemotherapeutic regimens have been reported by a number of investigators. While many authors have advocated supportive care alone because "current treatments have not demonstrated increased survival," we believe patients with mesothelioma should be offered investigational therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

An ultrastructural comparison of mesotheliomas with adenocarcinomas of the lung and breast

The ultrastructural features of 15 mesotheliomas were compared with those of equal numbers of adenocarcinomas of the lung and of the breast in a double-blind study. Combined quantitative and qualitative features were evaluated to provide criteria for distinguishing among these three tumors, which may present as either primary or metastatic pleural tumors. mesotheliomas could be distinguished from adenocarcinomas of the lung by length of microvilli (mean ratios of length to diameter [LDR], 15.7 and 8.7, respectively; P less than 0.01) and content of tonofilaments. Length of microvilli was also useful in distinguishing mesotheliomas from breast adenocarcinomas (mean LDR, 15.7 and 6.9, respectively; P less than 0.001). Adenocarcinomas of the lung could be distinguished from adenocarcinomas of the breast by tonofilament content and the presence of intracytoplasmic lumina. Combined quantitative and qualitative criteria are essential for maximal ultrastructural discrimination among these tumors.

Keratin proteins and carcinoembryonic antigen in synovial sarcomas: an immunohistochemical study of 24 cases

Twenty-four synovial sarcomas were examined for the presence of keratin proteins by an indirect immunoperoxidase method with paraffin-embedded tissues. Keratin proteins were identified in 16 of 24 cases (67 per cent). Both the pseudoglandular and spindle cell areas of all eight of the biphasic synovial sarcomas and the spindle cells of eight of the 16 monophasic synovial sarcomas contained keratin proteins. In spindle cell areas, staining was observed in single cells and small cords and clusters of cells in the absence of cleft formation or other evidence of a pseudoglandular component. The predominant cytologic staining pattern in all cases was peripheral, with localization of staining to the cell membrane or adjacent areas, but diffuse and focal cytoplasmic staining patterns were also observed. No staining for keratin proteins was seen in 101 control cases, including 52 sarcomas of various types. Carcinoembryonic antigen was also identified in four of the 24 synovial sarcomas by an indirect immunoperoxidase technique. The identification of keratin proteins may be helpful in the pathologic diagnosis of synovial sarcoma, particularly the spindle cell monophasic variant.