Abstract P5-14-08: Prospective phase II study of concurrent capecitabine and radiation demonstrates futility in triple negative chemo-resistant breast cancer

Background: Capecitabine is an established radiosensitizer in rectal and other cancers. We conducted a prospective single arm phase II study to examine the response rate of gross chemo-refractory breast cancer treated with concurrent capecitabine and radiotherapy.

Methods: Patients who had inoperable or marginally operable gross disease in the breast and/or lymph node(s) after chemotherapy or gross disease on the chest wall or in the regional lymphatics after mastectomy were eligible. Patients 1-9 received capecitabine 825 mg/m2 BID daily beginning on the first day of radiotherapy. Excess grade 3 toxicity (%) was observed; the protocol was amended and subsequent patients received drug only on radiation treatment days. Radiation dose was at the discretion of the treating physician (50Gy-72 Gy, with no more than 2.5 Gy/fraction). Response was assessed by a single physician using paired radiation planning CTs (pretreatment and on-treatment after 45 Gy). Clinical correlation to all other available imaging was also made. Kaplan-Meier curves were used to estimate overall survival (OS) and local recurrence-free survival (LRFS). Circulating tumor cells (CTCs) in blood were examined in consenting patients.

Results: The trial was stopped early after an unplanned interim analysis prompted by slow accrual suggested futility independent of response. From 2009-2012, 32 patients were accrued; 26 completed protocol specific treatment (17 post-mastectomy radiation with gross nodes, 4 pre-op, 5 aggressive palliation) and are included in this analysis. Median follow up was 7.3 months (interquartile range 6.7 – 17.4). Nineteen patients (73%) had a partial or complete response. Fourteen patients (53.9%) experienced at least one grade 3 non-dermatitis toxicity including 7/9 treated with continuous dosing. Four inoperable patients were treated with pre-op radiation therapy and 3 converted to operable. None achieved a pCR or near pCR. One-year actuarial OS was 52%. There was no difference in OS comparing among PMRT vs. preoperative or palliative RT (P = 0.90). One-year actuarial local recurrence free survival among PMRT patients was 38%. Ten patients had triple negative (TN) receptor status. There was no difference in radiation response by receptor status (P = 0.56); however, treatment was deemed subjectively futile (i.e., converted to operable but death secondary to new widespread M1 disease immediately post-op) in 9 of the 10 patients with TN disease versus 6 of the 16 patients with non-TN disease (P = 0.014). Median OS and 1-yr actuarial OS, among non-TN vs. TN patients were not reached vs. 6.1 months and 77% vs. 10% (P < 0.001), respectively. Eight/fifteen patients tested were positive for CTCs. CTCs did not correlate to receptor status, futility of RT or OS.

Conclusions: Capecitabine can be safely administered as a daily concurrent chemoradiation regimen with weekend holidays. However, in this small, prospective and selected cohort, concurrent chemoradiation with capecitabine was futile among patients with TN breast cancer. Alternative strategies are urgently needed in TN patients.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-14-08.

Relationship between implementation of the American Society of Clinical Oncology/College of American Pathologists guideline recommendations for breast core-needle biopsies and delay in therapy for patients with breast cancer

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Background: Recently the ASCO/CAP suggested new guideline recommendations for immunohistochemical (IHC) testing of biomarkers in breast cancer. An algorithm that relies on accurate, reproducible assay performance was proposed and preanalytical, analytical and postanalytical standards suggested. One such recommendation is to have appropriate internal controls when assessing hormone expression. In this retrospective study we evaluated 242 breast core biopsy specimens to assess the impact of the recently proposed ASCO/CAP guideline recommendations and its possible impact on routine daily practice. In addition, we explore the impact of blindly selecting a random core for potential future studies.

Methods: A total 988 cores from 242 specimens corresponding to 224 patients diagnosed between 2008 and 2009 were examined. Each core was examined for the presence of normal glands, percentage of tumor involvement, biomarker status, and diagnostic adequacy.

Results: Absence of normal glands was found on 61/242 specimens (25%). Of these, expression of ER, PR and HER2 was seen in 44 (72%), 28 (46%), and 21 specimens (35%) respectively. Negative staining for ER, PR and HER2 was observed in 7 specimens (12%). A total of 148 cores (15%) showed absence of tumor and 275 cores (28%) had <25% of tumor in them. 18 cores (2%) were insufficient for diagnosis due to either scant tumor present or crush artifact present.

Conclusions: Although the presence of internal control glands is optimal, its presence may be unnecessary if proper IHC batch run controls are utilized and histologic/IHC concordance is performed. Tumor histology and IHC profile concordance is imperative specially in triple negative cases. The impact on patient health care of an “receptor uninterpretable” biopsy is yet to be determined, but likely would include assessment of the delay in care due to a repeat biopsy with procurement of additional tissue, additional heath care costs, and anxiety to the patient. Adequacy check using frozen section could be done to assess for the presence of tumor during the procedure.

Wide-field imaging of fluorescent deoxy-glucose in ex vivo malignant and normal breast tissue

Rapid in situ determination of surgical resection margins during breast cancer surgery would reduce patient time under anesthesia. We present preliminary data supporting the use of a fluorescent glucose analog (2-NBDG) as an optical contrast agent to differentiate freshly excised breast tissue containing cancerous cells from normal breast tissue. Multi-spectral images of 14 breast cancer specimens acquired before and after incubation with 2-NBDG demonstrated increased fluorescent signal in all of the malignant tissue due to increased 2-NBDG consumption. We demonstrate that 2-NBDG has potential as an optical contrast agent to differentiate cancerous from non-cancerous tissue.

Neovascularization in mucinous ductal carcinoma in situ suggests an alternative pathway for invasion

AIMS

Ductal carcinoma in situ (DCIS) associated with invasive mucinous carcinoma (IMC) has not been well characterized. The aim was to characterize mucinous DCIS (mDCIS) of the breast and to describe, to our knowledge for the first time, neovascularization in mucin.

METHODS AND RESULTS

The pathology reports and slides were reviewed from 44 patients treated between 2003 and 2006 at The University of Texas M. D. Anderson Cancer Center, whose diagnosis fulfilled the criteria of IMC or DCIS with mucin production. The patients, all female, had a mean age of 62 years. DCIS was present in 93% of cases and the predominant histological types were solid, cribriform and micropapillary. The DCIS was grade 1 in 12 of 41 cases (29.3%), grade 2 in 25 of 41 cases (61%) and grade 3 in four of 41 cases (9.8%). Mucin was seen in the lumen of the ducts involved by DCIS in 88% of cases, mucin and vessels in 63.4% of cases and neither mucin nor vessels in 12.2%. The DCIS was vascular endothelial growth factor-positive, platelet-derived growth factor receptor-beta-positive and CDX-2-negative (100%). Occasional luminal cells within the DCIS were immunopositive for CD68.

CONCLUSIONS

A significant number of mDCIS showed neovascularization in intraluminal mucin. When identified on core needle biopsy, the presence of vascularized mucin should not be used alone to discriminate between invasive and in situ carcinoma. A hypothesis proposed for the source of recruitment of vessels in the mucin is that mucin can promote neovascularization and that tumour cells invade not into the adjacent fibroconnective tissue, but rather into the mucinous, richly vascularized stroma that they have induced. Alternatively, it is possible that both cells and their secretory product invade together. To our knowledge, this is the first study to characterize neovascularization within the mucinous component of DCIS associated with and without IMC.

Loss of myoepithelium is variable in solid papillary carcinoma of the breast

AIMS

Reports on the frequency of myoepithelial loss in solid papillary carcinoma (SPC) of the breast, an unusual variant of papillary carcinoma with a solid pattern of expansile growth, have been strikingly contradictory. The aim was to clarify the frequency of myoepithelial loss in cases of SPC diagnosed at our institution.

METHODS AND RESULTS

Eleven cases of SPC with available blocks or unstained slides were retrieved from the M. D. Anderson archives or obtained from outside contributors. Immunohistochemistry for smooth muscle actin (SMA) and p63 was evaluated on the circumscribed nests that appeared to be non-invasive by haematoxylin and eosin morphology. Three of the 11 cases (27%) were positive for both SMA and p63 at the periphery of all such foci, whereas eight cases (73%) lacked staining for both myoepithelial markers in at least one focus. Of these eight cases, one was diagnosed with only microinvasion, yet metastatic tumour resembling the circumscribed primary SPC was identified in two ipsilateral axillary lymph nodes.

CONCLUSIONS

SPC of the breast frequently lacks myoepithelial markers at the tumour-stromal interface in spite of a circumscribed non-invasive appearance. Metastases from such tumours are infrequent, but can occur in cases that lack myoepithelial marker expression by immunohistochemistry.

Expression of ER? and ER? in lobular carcinoma in situ

AIMS

Oestrogen is a modulator of cell growth and differentiation in the breast. It mediates most of its function through members of the oestrogen receptor (ER) family, ERalpha and ERbeta. Lobular carcinoma in situ (LCIS) is a known risk factor for the development of breast cancer; however, the use of tamoxifen for prevention is based upon data for ER+ (ERalpha) LCIS associated with invasion, but limited data exist on the use of tamoxifen in cases of ER+ (ERalpha) LCIS occurring in the absence of invasive carcinoma. The aim of this study was to examine ER expression in LCIS to determine the relationship of ERalpha to ERbeta and, thereby, to determine whether it is of clinical value to measure ERbeta along with ERalpha.

METHODS AND RESULTS

Core biopsy specimens from 50 patients were examined retrospectively. Histology was reviewed and histological parameters were assessed. Formalin-fixed paraffin-embedded tissue was available for E-cadherin, ERalpha and ERbeta immunohistochemistry. The degree of ERalpha and ERbeta nuclear reactivity was quantified. The patients' mean age was 55 years. The mean follow-up duration was 48 months. All 50 cases of LCIS were E-cadherin-negative. All cases were ERalpha+ and ERbeta+. The staining intensity of ERbeta was strong and included staining of periductal stromal cells. The median percentage of cells immunoreactive for ERalpha was 75% and for ERbeta 70% (range 10% weak positive to 100% strong positive). There was a statistically significant relationship between ERbeta staining intensity and incidence of ipsilateral breast cancer (P = 0.010).

CONCLUSIONS

The presence and intensity of both stromal and glandular ERbeta immunoreactivity suggest that the action of oestrogen on LCIS is on both stromal and glandular cells. Future studies are needed to determine whether the presence of ERbeta in LCIS could be targeted to influence the treatment of this disease and perhaps alter its natural history.

Recommendations for sentinel lymph node processing in breast cancer

The status of the sentinel lymph node (SLN) has been shown to accurately reflect the presence or absence of metastases in the axilla in patients with breast cancer. This study was designed to determine the optimal protocol for SLN processing. A total of 173 SLNs from 96 breast cancer patients who had successful SLN localization and underwent completion axillary node dissection were identified. All SLNs were negative for metastases by initial routine histologic evaluation. The nodes were submitted in a total of 300 blocks. Each block was serially sectioned to produce 10 levels. Pan-cytokeratin stain was performed on levels 3 and 8. All other levels were stained with hematoxylin and eosin. Metastases were identified in 22 SLNs from 19 patients by examining all 10 levels. The first two hematoxylin and eosin- or the first cytokeratin-stained levels were positive for metastases in 21 (95.5%) of the 22 positive SLNs. Two additional hematoxylin and eosin-stained and one cytokeratin-stained levels of each SLN correctly identified the status of the node in 94 (97.9%) of 96 patients. Therefore, we recommend that after an initial hematoxylin and eosin-stained section, two additional hematoxylin and eosin-stained sections and one cytokeratin-stained section should be evaluated.

Metastases to breast simulating ductal carcinoma in situ: report of two cases and review of the literature

The breast is an uncommon site for metastases. Nevertheless, it is important to differentiate primary from secondary tumors of the breast, because clinical management and expected outcomes are vastly different. We report two examples of tumors with a papillary histologic pattern metastasizing to the breast. One of the cases occurred in a 31-year-old woman with a primary renal cell carcinoma, the other was in a 42-year-old woman with an ovarian papillary serous adenocarcinoma. In the first case, the patient's previous history of cancer was not known to the pathologist. The cases highlight the difficulty in distinguishing primary from metastatic tumors in the breast. In both cases the tumors infiltrated in a pattern that mimicked in situ ductal carcinoma changes. Additionally, in both cases, the metastasizing tumor was unusual with the tumor cells diffusely permeating the lymphatic spaces, not in a solid mass. These cases and a review of the literature indicated that breast metastases, although rare, must be recognized and differentiated from primary breast tumors to avoid unnecessary radical surgery to the breast. Moreover, the presence of changes similar to in situ carcinoma of the breast are not conclusive evidence that one is evaluating a primary breast carcinoma. When there is any unusual histomorphology, a good degree of suspicion is necessary. Ann Diagn Pathol 5:15-20, 2001.

Pigmented renal clear cell carcinoma with melanocytic differentiation

Renal cell carcinoma (RCC) is the most common malignant tumor of the adult kidney, and its incidence has been steadily rising. RCC consists of several subtypes, each of which has its own clinical features, and cytogenetic and molecular characteristics. Recognizing histologic patterns of RCC is important not only for correct diagnosis, but also for providing insight into the biological behavior of the tumor and subsequent appropriate medical care for the patient. Pigments other than hemosiderin has been observed in RCC, but none of them have been proved to be melanin. Melanotic tumors, either primary or metastatic, are rare in the kidney. We present an unusual case of melanin-pigmented clear cell RCC with melanocytic differentiation, an unusual variant that may lead to errors in diagnosis and treatment.

Pleomorphic lobular carcinoma: morphology, immunohistochemistry, and molecular analysis

Infiltrating pleomorphic lobular carcinoma (PLC) is an aggressive variant of infiltrating lobular carcinoma. Recently, in situ changes identical to PLC (PLCIS) have been described. The role of prognostic markers and their correlation with therapeutics, clinical outcome, and genetic changes is not well established in PLC. The authors examined 38 cases of this entity to understand better this tumor's biology. Immunohistochemical (IHC) analysis was performed in 21 specimens for estrogen and progesterone steroid receptors, p53, Her 2 (p185), and GCDFP-15. Genomic deoxyribonucleic acid was obtained from microdissected tumor as well as normal control cells, and loss of heterozygosity was investigated at the ESR (16q24), p53 (TP53 17p), Her 2 (17q 11-12), and BRCA 1 (17q12-25) loci. In this series, the average patient age was 57.5 years (age range, 24-92 years). Twenty-seven women were postmenopausal. Tumor size ranged from 1.2 to 25 cm. Six patients were a pathologic stage I; 19, stage II; 12, stage III; and one, stage IV. Histologically, multifocal nodular aggregates of discohesive pleomorphic tumor cells were seen interspersed in dense and fibrotic breast parenchyma. Twenty-nine percent of the specimens demonstrated associated signet ring cells. The remainder had dishesive, globoid, plasmacytoid cells with high-grade nuclear features. PLCIS was identified in 17 of 38 patients (45%), and lobular carcinoma in situ (LCIS) was noted in 8 patients (21%). IHC analysis showed estrogen immunoreactivity in 81%, progesterone in 67%, GCDFP-15 in 71%, and Her 2 in 81% (2+ to 3+ membranous staining) of specimens. Antibodies to p53 stained the tumor cell nuclei in 48% of the tumors. Loss of heterozygosity was identified in 52% of the specimens at the p53 locus, 18% at the ESR locus, 19% to 24% at the Her 2 loci, and 27% to 32% at the BRCA 1 locus. Follow-up was available in 19 patients and ranged from 12 months to 15 years (mean, 73 months). Seven patients had no evidence of disease at last examination (range, 1-15 years), three patients were alive with disease (range, 2-14 years), and nine patients were dead of disease (range, 2 months-9 years). Six patients had subsequent diagnoses of tumor in the contralateral breast. Analysis shows that PLC tends to appear in older postmenopausal women who present with locally advanced disease. PLCIS was found to be associated with PLC 45% of the time. The aggressive clinical course of patients with PLC is supported by tumor immunoreactivity with unfavorable markers Her 2 and p53. Overexpression of Her 2 in PLC may be therapeutically relevant, enabling the use of novel chemotherapeutic drugs like Herceptin. Interestingly, tumors that were Her 2 immunoreactive also maintained estrogen hormone immunoreactivity.

Response during radiotherapy may be associated with outcome in mediastinal Hodgkin's disease

A relationship between the rate of regression of lymphomas treated with chemotherapy and long-term outcome has been observed. This study was undertaken to determine if the rate of tumor regression during radiotherapy for mediastinal Hodgkin's disease is a predictor of in-field recurrence. Twenty-nine patients with early-stage Hodgkin's disease treated with radiotherapy alone as part of an NCI randomized trial had both a non-massive mediastinal component of disease and all requisite simulation and port films available for analysis. The histology was nodular sclerosis in all patients. Stage distribution was as follows: IA-1; IIA-17; IIB-8; IIIA1-3. The median age was 27 years and the median radiation dose was 4470 cGy. A mediastinal mass ratio was calculated from each patient's simulation and weekly port films by dividing the width of the mediastinal mass by the intrathoracic diameter at the level of the carina. Histopathologic correlation was also done to quantify the degree of tumor vs. sclerosis in the specimens. Univariate analysis and Cox proportional hazards analysis were used to study the association between several covariates (stage, sex, symptoms, extra-lymphatic disease, initial mediastinal mass ratio, age, dose, percent tumor in the specimen, and cumulative percentage of tumor regression) and time to in-field recurrence, as well as probability of any failure. Univariate analysis indicates that lower dose, higher percent tumor in the specimen, and lower cumulative percent regression are statistically significant predictors for in-field recurrence, as well as for any failure. By Cox regression analysis, cumulative percent regression is the sole factor independently associated with in-field recurrence (two-tailed P=0.04). The percent tumor in the specimen is the only factor similarly identified for time to any failure (two-tailed P=0.02). Histopathologic correlation suggests that patients with early stage mediastinal Hodgkin's disease who demonstrate a high percent tumor in the specimen may be at increased risk of failure. Patients with a low cumulative percent regression during radiotherapy appear to be at an increased risk of in-field recurrence.

Allelic loss on chromosome arm 8p: analysis of sporadic epithelial ovarian tumors

OBJECTIVE

Our objective was to determine the frequency of allelic loss at 8p21 in sporadic epithelial ovarian cancer. We recently described allelic loss at this locus in 7/9 ovarian cancers from patients with BRCA1 gene mutations.

METHODS

We anonymously obtained and examined 40 unselected invasive epithelial ovarian cancers and 5 low-malignant-potential (LMP) ovarian tumors for loss of heterozygosity (LOH) at 8p12-22. Pure epithelial and stromal cell populations were procured selectively by laser capture microdissection and extracted DNA was amplified with polymorphic microsatellite markers spanning the region of interest.

RESULTS

LOH was highest (50%) at marker D8S136 located at 8p21 with 15 of 30 informative cases exhibiting an allelic deletion. None of the LMP tumors evaluated showed LOH at 8p12-22. A trend toward more frequent LOH at 8p12-22 was identified with increasing disease aggressiveness from LMP to early stage invasive ovarian cancer to advanced stage invasive ovarian cancer (Lehman's test, P2 < 0.024).

CONCLUSIONS

Fifty percent allelic loss at the distal portion of 8p21 has not been reported to date for sporadic epithelial ovarian carcinomas. The higher rate of loss in our cohort, in contrast to previous allelotyping studies, is due likely to analysis from homogenous cell populations. These results, in concert with our previous study of BRCA1 mutation-positive patients, suggest a tumor suppressor gene locus at 8p21 for epithelial ovarian cancer.

Infiltrating micropapillary carcinoma of the breast

Infiltrating micropapillary carcinoma of the breast is a recently described and poorly recognized aggressive variant of infiltrating ductal carcinoma for which the clinical significance and role of prognostic markers are not fully described. In 14 cases of infiltrating micropapillary carcinoma, we studied histologic characteristics; immunohistochemical expression of c-erbB-2, p53, and MIB-1; hormonal expression of these tumors; and genetic alterations on the p53 locus. We correlated these results with clinical outcome. Patient ages ranged from 37 to 58 years (mean, 50 yr). Nine patients presented with a palpable tumor, one with an axillary mass. Three patients had abnormal mammograms. Five patients (36%) presented with Stage II disease, eight (57%) with Stage III, and one (7%) with Stage IV. The tumors were a modified Bloom-Richardson Grade II in nine cases (64%) and Grade III in 5 (36%). Mitoses ranged from 1 to 12 per 10 high power fields. Necrosis was uniformly absent. Psammoma bodies were present in 9 cases (64%) and lymphatic invasion in 10 (71%). In all of the cases, c-erbB-2 was identified immunohistochemically, and MIB-I was positive, staining 30 to 60% of the tumor cells. The cells were immunoreactive for p53 in six (75%) of eight cases, and, when present, stained 20 to 50% of the tumor cells. Loss of heterozygosity on locus 17p13.1 (p53) was identified in 4 of 5 informative samples. Molecular and immunohistochemical analyses had an 80% concordance. Follow-up was available in 11 patients, of whom 9 had recurrence in the skin and chest wall (average time of recurrence, 24 mo). Recognition of this distinctive and aggressive variant of infiltrating carcinoma is important because of its unfavorable prognosis and specific pattern of local recurrence. Its aggressive nature is supported by its advanced stage at presentation and expression of unfavorable prognostic markers.

Synchronous inflammatory breast cancer and advanced ovarian carcinoma: a case with prolonged disease-free survival

Despite the known association of these malignancies, the incidence of a synchronous presentation of breast and ovarian cancer is low, and the current literature does not address an approach to this clinical problem directly. We report a greater than 2.5 year disease-free survival in a patient treated for synchronous stage IIIB inflammatory breast cancer and stage IIIC epithelial ovarian cancer. The prolonged disease-free survival in our case may provide some guidance in this unusual clinical situation.

Male adnexal tumour of probable Wolffian origin occurring in a seminal vesicle

AIMS

Adnexal tumours of probable Wolffian origin are rare low-grade malignant neoplasms that have been previously described in the broad ligament, ovaries and retroperitoneum of females. All are characterized by small, bland epithelial cells growing in a diffuse, trabecular, or tubular pattern. The majority of the cases reported have pursued a benign clinical course. However, recurrences and distant metastases have been described. We present a case of a male adnexal tumour of probable Wolffian origin occurring in the left seminal vesicle of a 29-year-old man with 23 years of follow-up.

RESULTS

The diagnosis is supported by immunohistochemical and electron microscopic findings: The tumour cells were immunoreactive for cytokeratin and vimentin while smooth muscle antigen and S100 protein were uniformly negative. By electron microscopy cells were arranged in an acinar pattern and surrounded flocculent, electron-dense material. Individual cells contained numerous dense bodies and free ribrosomes. The patient had recurrences at 14 and 23 years after initial diagnosis.

CONCLUSION

This is the first report of this entity in a male. The literature on this unusual tumour is reviewed and the clinicopathological, immunohistochemical and ultrastructural features are described. The differential diagnosis of this seemingly indolent tumour is discussed with genitourinary tumours having a more aggressive clinical course.

Allelic loss on chromosome 22q in epithelioid sarcomas

Epithelioid sarcomas are soft tissue tumors with an indolent, but potentially aggressive, clinical behavior. Distinction from other benign and malignant entities may be a diagnostic dilemma. In this study, we evaluate the presence of loss of heterozygosity (LOH) of chromosome 22q in tumor DNA from 13 epithelioid sarcomas, four epithelioid angiosarcomas, and two epithelioid hemangioendotheliomas, and investigate its possible role in diagnosis. LOH was detected in 6 of 10 (60%) of the informative epithelioid sarcomas. No allele loss was detected in the informative vascular tumors, three angiosarcomas, and two hemangioendotheliomas. Chromosome 22q carries the locus of a tumor suppressor gene, the neurofibromatosis 2 (NF2) gene, which has been shown to be lost or mutated in some NF2-related tumors, sporadic meningiomas, and vestibular schwannomas, as well as a few other tumors. Our data suggest that a region of chromosome 22q may be the locus of a tumor suppressor gene involved in the tumorigenesis of these neoplasms. Genetic alterations of yet-unknown tumor suppressor genes in this region, or even the NF2 tumor suppressor gene, may play a role in epithelioid sarcomas tumorigenesis. The fact that LOH was only detected in epithelioid sarcomas and not in the vascular tumors studied suggests a possible role for this marker in diagnosis.

The histological spectrum of hemangiopericytoma: application of immunohistochemical analysis including proliferative markers to facilitate diagnosis and predict prognosis

Hemangiopericytoma (HPC) is an uncommon vascular neoplasm thought to be derived from pericytes. Prediction of patient outcome is difficult based what is currently known about these tumors and histological parameters alone. We compiled 27 cases of HPC and evaluated the spectrum of histological features to investigate whether there was any correlation between histology, immunostaining, prognostic markers, and patient outcome. The following parameters were evaluated: vasculature, histological pattern (solid, myxoid, trabecular, alveolar), degree of cellular pleomorphism, necrosis, mitoses, and giant cell content. Immunohistochemistry was performed to determine the reactivity for CD 31, CD34, vimentin, actin, cytokeratin, S100, actin, and SMA. Proliferative rate was analyzed using antibodies to PCNA and MIB1. Patient's age ranged from 8 months to 75 years (mean, 35; median, 31). Twenty of 27 cases were located in the extremities. The tumors were grossly described as lobulated and well circumscribed (n=12) and nonencapsulated (n=15). By histology, the characteristic ramifying or staghorn vasculature pattern was seen in all cases. A solid histological pattern was mixed with an alveolar pattern in three cases, trabecular pattern in six cases, and myxoid pattern in two cases. Tumor cells were uniform, polygonal to spindle-shaped, often with vesicular nuclei. Tumor giant cells were present in 9 of 27 cases; necrosis, in 11 of 27. Mitoses ranged from 0 to 14 per 10 high-power fields (HPF). Cellular pleomorphism was 1+ in nine cases, 2+ in 12 cases, and 3+ in six cases. Immunohistochemistry showed reactivity for CD34 and vimentin in all cases. Actin was focally positive in one case, and SMA was focally positive in another. CD 31, cytokeratin, and S100 were uniformly nonreactive. Proliferative index measured by PCNA and MIBI ranged between less than 1% and 40% of tumor cells. Follow-up was available in 22 cases and ranged from 1 year to 15 years. Seven patients had metastases, and two recurred locally. Thirteen patients had no evidence of disease at last checkup. Parameters associated with recurrences or metastases include a trabecular pattern, the presence of necrosis, mitoses, vascular invasion, and cellular pleomorphism. Features associated with an aggressive biological behavior can be identified histologically. There was some, but not total, correlation between proliferative markers and tumor aggressiveness.