Comparison of three scoring methods using the FDA-approved 22C3 immunohistochemistry assay to evaluate PD-L1 expression in breast cancer and their association with clinicopathologic factors.

BACKGROUND: In the evaluation of PD-L1 expression to select patients for anti-PD-1/PD-L1 treatment, uniform guidelines that account for different immunohistochemistry assays, different cell types and different cutoff values across tumor types are lacking. Data on how different scoring methods compare in breast cancer are scant. METHODS: Using FDA-approved 22C3 diagnostic immunohistochemistry assay, we retrospectively evaluated PD-L1 expression in 496 primary invasive breast tumors that were not exposed to anti-PD-1/PD-L1 treatment and compared three scoring methods (TC: invasive tumor cells; IC: tumor-infiltrating immune cells; TCIC: a combination of tumor cells and immune cells) in expression frequency and association with clinicopathologic factors. RESULTS: In the entire cohort, positive PD-L1 expression was observed in 20% of patients by TCIC, 16% by IC, and 10% by TC, with a concordance of 87% between the three methods. In the triple-negative breast cancer patients, positive PD-L1 expression was observed in 35% by TCIC, 31% by IC, and 16% by TC, with a concordance of 76%. Associations between PD-L1 and clinicopathologic factors were investigated according to receptor groups and whether the patients had received neoadjuvant chemotherapy. The three scoring methods showed differences in their associations with clinicopathologic factors in all subgroups studied. Positive PD-L1 expression by IC was significantly associated with worse overall survival in patients with neoadjuvant chemotherapy and showed a trend for worse overall survival and distant metastasis-free survival in triple-negative patients with neoadjuvant chemotherapy. Positive PD-L1 expression by TCIC and TC also showed trends for worse survival in different subgroups. CONCLUSIONS: Our findings indicate that the three scoring methods with a 1% cutoff are different in their sensitivity for PD-L1 expression and their associations with clinicopathologic factors. Scoring by TCIC is the most sensitive way to identify PD-L1-positive breast cancer by immunohistochemistry. As a prognostic marker, our study suggests that PD-L1 is associated with worse clinical outcome, most often shown by the IC score; however, the other scores may also have clinical implications in some subgroups. Large clinical trials are needed to test the similarities and differences of these scoring methods for their predictive values in anti-PD-1/PD-L1 therapy.

A Clinical Feasibility Trial for Identification of Exceptional Responders in Whom Breast Cancer Surgery Can Be Eliminated Following Neoadjuvant Systemic Therapy.

OBJECTIVE: To determine the accuracy of fine-needle aspiration (FNA) and vacuum-assisted core biopsy (VACB) in assessing the presence of residual cancer in the breast after neoadjuvant systemic therapy (NST). SUMMARY BACKGROUND DATA: Pathologic complete response (pCR) rates after NST have improved dramatically, suggesting that surgery might be avoided in some patients. Safe avoidance of surgery would require accurate confirmation of no residual invasive/in situ carcinoma. METHODS: Forty patients with T1-3N0-3 triple-negative or HER2-positive cancer receiving NST were enrolled in this single-center prospective trial. Patients underwent ultrasound-guided or mammography-guided FNA and VACB of the initial breast tumor region before surgery. Findings were compared with findings on pathologic evaluation of surgical specimens to determine the performance of biopsy in predicting residual breast disease after NST. RESULTS: Median initial clinical tumor size was 3.3 cm (range, 1.2-7.0 cm); 16 patients (40%) had biopsy-proven nodal metastases. After NST, median clinical tumor size was 1.1 cm (range, 0-4.2 cm). Nineteen patients (47.5%) had a breast pCR and were concordant with pathologic nodal status in 97.5%. Combined FNA/VACB demonstrated an accuracy of 98% (95% CI, 87%-100%), false-negative rate of 5% (95% CI, 0%-24%), and negative predictive value of 95% (95% CI, 75%-100%) in predicting residual breast cancer. VACB alone was more accurate than FNA alone (P = 0.011). CONCLUSIONS: After NST, image-guided FNA/VACB can accurately identify patients with a breast pCR. Based on these results, a prospective clinical trial has commenced in which breast surgery is omitted in patients with a breast pCR after NST according to image-guided biopsy.

Comparative Effectiveness of an mTOR-Based Systemic Therapy Regimen in Advanced, Metaplastic and Nonmetaplastic Triple-Negative Breast Cancer.

BACKGROUND: Triple-negative breast cancer (TNBC) is a heterogeneous disease with subtypes having different "targetable" molecular aberrations. Metaplastic breast cancers (MpBCs) are typically TNBCs and commonly have alterations in the PI3K/Akt/mTOR pathway. We previously reported efficacy for an mTOR-based chemotherapy regimen in MpBC. To determine if tumor subtype influences prognosis, we compared treatment outcomes of patients with MpBC with those of patients with nonmetaplastic TNBC receiving an mTOR-based systemic therapy regimen. PATIENTS AND METHODS: Patients with advanced MpBC and nonmetaplastic TNBC were treated at our institution from April 16, 2009, through November 4, 2014, using mTOR inhibition (temsirolimus or everolimus) with liposomal doxorubicin and bevacizumab (DAT/DAE). Median progression-free survival (PFS) and overall survival (OS) were estimated by the Kaplan-Meier method. Cox regression analyses were used to evaluate associations between tumor histology and outcomes. Multivariable models were adjusted for all covariates. RESULTS: Fourteen patients with nonmetaplastic TNBC and 59 patients with advanced MpBC were treated with DAT/DAE. MpBC patients were older (p = .002) and less likely to have a history of bevacizumab use (p = .023). Median PFS for the nonmetaplastic TNBC and MpBC patients was 2.5 months and 4.8 months, respectively. This difference in PFS was statistically significant on univariable (p = .006) but not multivariable analysis (p = .087). Median OS for the nonmetaplastic TNBC and MpBC patients was 3.7 months and 10.0 months, respectively (p = .0003). MpBC remained significantly associated with improved OS on multivariable analysis (p < .0001). CONCLUSION: In our study, DAT/DAE appeared to be more effective in MpBC compared with nonmetaplastic TNBC. These data support patient selection for targeted therapy in TNBC. IMPLICATIONS FOR PRACTICE: Metaplastic breast cancers (MpBCs) represent <1% of all breast cancers, demonstrate mesenchymal differentiation, and are typically resistant to chemotherapy. Patients with advanced MpBC treated with an mTOR-based systemic therapy regimen had better long-term outcomes compared with patients with nonmetaplastic triple-negative breast cancer treated with the same regimen, suggesting that metaplastic histology may predict benefit from agents targeting the PI3K/Akt/mTOR pathway.

Targeting RPL39 and MLF2 reduces tumor initiation and metastasis in breast cancer by inhibiting nitric oxide synthase signaling.

We previously described a gene signature for breast cancer stem cells (BCSCs) derived from patient biopsies. Selective shRNA knockdown identified ribosomal protein L39 (RPL39) and myeloid leukemia factor 2 (MLF2) as the top candidates that affect BCSC self-renewal. Knockdown of RPL39 and MLF2 by specific siRNA nanoparticles in patient-derived and human cancer xenografts reduced tumor volume and lung metastases with a concomitant decrease in BCSCs. RNA deep sequencing identified damaging mutations in both genes. These mutations were confirmed in patient lung metastases (n = 53) and were statistically associated with shorter median time to pulmonary metastasis. Both genes affect the nitric oxide synthase pathway and are altered by hypoxia. These findings support that extensive tumor heterogeneity exists within primary cancers; distinct subpopulations associated with stem-like properties have increased metastatic potential.

Low expression of galectin-3 is associated with poor survival in node-positive breast cancers and mesenchymal phenotype in breast cancer stem cells.

BACKGROUND: Galectin-3 (Gal3) plays diverse roles in cancer initiation, progression, and drug resistance depending on tumor type characteristics that are also associated with cancer stem cells (CSCs). Recurrence of breast carcinomas may be attributed to the presence of breast CSCs (BCSCs). BCSCs exist in mesenchymal-like or epithelial-like states and the transition between these states endows BCSCs with the capacity for tumor progression. The discovery of a feedback loop with galectins during epithelial-to-mesenchymal transition (EMT) prompted us to investigate its role in breast cancer stemness. METHOD: To elucidate the role of Gal3 in BCSCs, we performed various in vitro and in vivo studies such as sphere-formation assays, Western blotting, flow cytometric apoptosis assays, and limited dilution xenotransplant models. Histological staining for Gal3 in tissue microarrays of breast cancer patients was performed to analyze the relationship of clinical outcome and Gal3 expression. RESULTS: Here, we show in a cohort of 87 node-positive breast cancer patients treated with doxorubicin-based chemotherapy that low Gal3 was associated with increased lymphovascular invasion and reduced overall survival. Analysis of in vitro BCSC models demonstrated that Gal3 knockdown by small hairpin RNA (shRNA) interference in epithelial-like mammary spheres leads to EMT, increased sphere-formation ability, drug-resistance, and heightened aldefluor activity. Furthermore, Gal3negative BCSCs were associated with enhanced tumorigenicity in orthotopic mouse models. CONCLUSIONS: Thus, in at least some breast cancers, loss of Gal3 might be associated with EMT and cancer stemness-associated traits, predicts poor response to chemotherapy, and poor prognosis.

GATA-binding protein 3 enhances the utility of gross cystic disease fluid protein-15 and mammaglobin A in triple-negative breast cancer by immunohistochemistry.

AIMS: We have demonstrated previously that gross cystic disease fluid protein-15 (GCDFP-15) and mammaglobin A (MAM) are of limited utility in triple-negative breast cancer (TNBC). GATA-binding protein 3 (GATA-3) is an emerging breast-associated immunohistochemical (IHC) marker with limited data in TNBC. Here, we examined GATA-3 expression in TNBC in comparison with GCDFP-15 and MAM. METHODS AND RESULTS: We studied GATA-3, GCDFP-15 and MAM IHC expression in 62 primary and 68 metastatic TNBCs. In primary TNBCs, GATA-3 staining was observed in 25 cases (40%), including 16 cases that were negative for GCDFP-15 and MAM. In metastatic TNBCs, GATA-3 staining was observed in 30 cases (44%), including 16 cases that were negative for GCDFP-15 and MAM. The expression frequency of any of the markers was 56% in primary and 62% in metastatic TNBCs. However, when focal staining was excluded, the expression frequency of any marker dropped to 31% and 44%, respectively. CONCLUSION: GATA-3 is expressed at a higher frequency by IHC in TNBC compared to GCDFP-15 and MAM, although the tissue specificity of the latter markers may be superior. When evaluating a triple-negative tumour, including GATA-3 in a panel of markers may increase the diagnostic accuracy for tissue origin in the appropriate clinical setting.

Gross cystic disease fluid protein-15 and mammaglobin A expression determined by immunohistochemistry is of limited utility in triple-negative breast cancer.

AIMS: In addition to oestrogen and progesterone receptors, gross cystic disease fluid protein-15 (GCDFP-15) and mammaglobin A (MAM) are the most common markers used to identify breast origin by immunohistochemistry. GCDFP-15 expression has been reported in approximately 60% of breast carcinomas and MAM expression in approximately 80%. Data on their expression in triple-negative breast cancer (TNBC) are very limited. The aim of this study was to examine the expression of these markers in TNBC to determine their utility in pathological diagnosis. METHODS AND RESULTS: We studied the immunohistochemical (IHC) expression of GCDFP-15 and MAM in 63 primary and 118 metastatic TNBCs. GCDFP-15 staining was present in 14% of primary and 21% of metastatic TNBCs. MAM staining was present in 25% of primary and 41% of metastatic TNBCs. The frequency of expression of GCDFP-15 and/or MAM was 30% in primary and 43% in metastatic TNBCs, and many positive tumours had only focal staining. CONCLUSIONS: Staining for GCDFP-15 and/or MAM in triple-negative carcinomas helps to confirm breast origin, but most tumours in this subgroup of breast carcinomas lack expression of either marker.

The role for sentinel lymph node dissection after neoadjuvant chemotherapy in patients who present with node-positive breast cancer.

BACKGROUND: Sentinel lymph node (SLN) dissection has been investigated after neoadjuvant chemotherapy and has shown mixed results. Our objective was to evaluate SLN dissection in node-positive patients and to determine whether postchemotherapy ultrasound could select patients for this technique. METHODS: Between 1994 and 2010, 150 patients with biopsy proven axillary metastasis underwent SLN dissection after chemotherapy and 121 underwent axillary lymph node dissection (ALND). Clinicopathologic characteristics were analyzed before and after chemotherapy. Statistical analyses included Fisher's exact test for nodal response and multivariate logistic regression for factors associated with false-negative events. RESULTS: Median age was 52 years. Median tumor size at presentation was 2 cm. The SLN was identified in 93 % (139/150). In 111 patients in whom a SLN was identified and ALND performed, 15 patients had a false-negative SLN (20.8 %). In the 52 patients with normalized nodes on ultrasound, the false-negative rate decreased to 16.1 %. Multivariate analysis revealed smaller initial tumor size and fewer SLNs removed (<2) were associated with a false-negative SLN. There were 63 (42 %) patients with a pathologic complete response (pCR) in the nodes. Of those with normalized nodes on ultrasound, 38 (51 %) of 75 had a pCR. Only 25 (33 %) of 75 with persistent suspicious/malignant-appearing nodes had a pCR (p = 0.047). CONCLUSIONS: Approximately 42 % of patients have a pCR in the nodes after chemotherapy. Normalized morphology on ultrasound correlates with a higher pCR rate. SLN dissection in these patients is associated with a false-negative rate of 20.8 %. Removing fewer than two SLNs is associated with a higher false-negative rate.

Imaging features of primary breast sarcoma.

OBJECTIVE: This purpose of this study is to describe the imaging findings in patients who presented with a diagnosis of primary breast sarcoma. MATERIALS AND METHODS: A search was performed of the pathology database at a single institution for patients with a histopathologic diagnosis of primary breast sarcoma or pure sarcomatoid carcinoma and who underwent preoperative mammography, sonography, or MRI. Patients with malignant phyllodes tumors were excluded. The imaging studies were retrospectively reviewed using the American College of Radiology BI-RADS lexicon. We documented clinical presentation, histopathologic characteristics, axillary nodal status, and the presence of distant metastases. RESULTS: Twenty-four women were included in the study; their mean age was 56 years (range, 21-86 years), and the mean tumor size was 6.1 cm (range, 0.9-15 cm). Only one tumor was identified in each patient. The predominant mammographic finding was a noncalcified oval mass with indistinct (9/14 [64%]) margins. Sonography most commonly revealed an oval (19/22 [86%]) solid mass with indistinct margins (17/22 [77%]). The masses were frequently hypoechoic (18/21 [86%]) and hypervascular (17/20 [85%]) and had posterior acoustic enhancement (13/21 [62%]). MRI showed a round or oval T2-hyperintense mass with irregular margins in four of five (80%) patients, and inhomogeneous enhancement was most common (3/4 [75%]). CONCLUSION: Primary breast sarcoma has imaging features that are not typically seen in infiltrating ductal carcinoma. A large oval hypervascular mass with indistinct margins should raise the suspicion for a primary breast sarcoma and prompt biopsy.

Invasive mammary carcinoma with neuroendocrine differentiation: histological features and diagnostic challenges.

AIMS: The aim of this study was to review the histomorphological features of primary neuroendocrine carcinomas (NEC) of the breast, in order to identify features useful in recognition of this entity for appropriate classification. METHODS AND RESULTS: 2003 World Health Organization (WHO) classification of tumors of the breast and female genital organs defined NEC of the breast as a subtype of invasive mammary carcinoma in which >50% of the tumor cells express neuroendocrine markers. Seventy-four cases that fulfilled the WHO diagnostic criteria for NEC of the breast, excluding small cell carcinoma and low-grade solid papillary carcinoma with a predominant in-situ component, were identified between 1984 and 2008 from MD Anderson Cancer Center, and were included in the study. NECs of the breast had variable histomorphological features. The most common histologic patterns were papillary (80%) and nested (64%). Mixed growth patterns were common (59%), including admixed ductal component. The tumor cells could be polygonal, round, plasmacytoid, spindled, or with signet ring cell features. The cytoplasm could be granular, eosinophilic, clear, or finely vacuolated. These tumors frequently mimicked invasive or in situ ductal carcinoma, or invasive lobular carcinoma. CONCLUSIONS: NEC of the breast is underrecognized. Careful attention to cytologic and architectural features can help to identify cases that require further immunophenotypic confirmation for correct tumor classification.

Metastatic neuroendocrine tumour in the breast: a potential mimic of in-situ and invasive mammary carcinoma.

AIMS: The aim of this study was to review the clinicopathological characteristics of neuroendocrine tumours (NETs) metastasizing to the breast, in order to identify features that could be useful in distinguishing these metastatic lesions from primary breast neoplasms. METHODS AND RESULTS: Eighteen metastatic NETs in the breast were identified from two large hospitals over a 15-year period. Eleven (62%) tumours originated in the gastrointestinal tract, 5 (28%) originated in the lung, and the other two were of indeterminate origin. Eight (44%) cases were initially misdiagnosed as primary mammary carcinomas. In retrospect, all metastatic tumours exhibited architectural and cytological features that would suggest neuroendocrine differentiation. Immunohistochemistry can further aid in the distinction between metastatic neuroendocrine and primary mammary carcinoma. All 11 tumours from the gastrointestinal tract expressed CDX-2, 3 (60%) of five tumours from the lung expressed thyroid transcription factor-1, and only 2 (11%) of 18 showed weak oestrogen receptor positivity. Additionally, unlike primary carcinomas, the majority (82%) of metastatic NETs were negative for cytokeratin 7, and all were negative for gross cystic disease fluid protein 15 and mammoglobin. CONCLUSIONS: There is a high propensity for metastatic NETs to mimic primary breast carcinomas. Careful attention to cytological and architectural features can help to identify cases that require further immunophenotypic workup with a panel of tissue-specific antibodies. However, clinical history is paramount for optimal diagnosis.

Lipomatous variant of myofibroblastoma with epithelioid features: a rare and diagnostically challenging breast lesion.

Myofibroblastoma of the breast is an unusual benign spindle cell tumor composed of cells with histologic, immunohistochemical, and ultrastructural features of myofibroblasts. In addition to the classic form, a few variants of myofibroblastoma have been described. Recognition of these variants is important to prevent overdiagnosis of a malignant lesion, especially on core biopsy. Three variants that can cause particular confusion on core biopsy are the lipomatous, infiltrative, and epithelioid variants of myofibroblastoma. Thus far, there have been only a few reports of these variants in the English literature. We report a rare case of a lipomatous variant of myofibroblastoma with an epithelioid cell component and discuss the differential diagnosis and potential diagnostic pitfalls.

Mammary-specific expression of Trim24 establishes a mouse model of human metaplastic breast cancer.

Conditional overexpression of histone reader Tripartite motif containing protein 24 (TRIM24) in mouse mammary epithelia (Trim24COE) drives spontaneous development of mammary carcinosarcoma tumors, lacking ER, PR and HER2. Human carcinosarcomas or metaplastic breast cancers (MpBC) are a rare, chemorefractory subclass of triple-negative breast cancers (TNBC). Comparison of Trim24COE metaplastic carcinosarcoma morphology, TRIM24 protein levels and a derived Trim24COE gene signature reveals strong correlation with human MpBC tumors and MpBC patient-derived xenograft (PDX) models. Global and single-cell tumor profiling reveal Met as a direct oncogenic target of TRIM24, leading to aberrant PI3K/mTOR activation. Here, we find that pharmacological inhibition of these pathways in primary Trim24COE tumor cells and TRIM24-PROTAC treatment of MpBC TNBC PDX tumorspheres decreased cellular viability, suggesting potential in therapeutically targeting TRIM24 and its regulated pathways in TRIM24-expressing TNBC.

Multimodality imaging of triple receptor-negative tumors with mammography, ultrasound, and MRI.

OBJECTIVE: We retrospectively reviewed imaging findings for 44 patients with triple receptor-negative breast carcinomas on mammography, sonography, and MRI to determine the imaging characteristics of triple receptor-negative cancers that may improve diagnosis at the time of presentation. CONCLUSION: Despite their large size at presentation, triple receptor-negative cancers may be occult on mammography or sonography and frequently have benign or indeterminate features. MRI identified all triple receptor-negative cancers and showed features that had a high positive predictive value for malignancy.

Rosai-Dorfman disease confined to the breast.

Rosai-Dorfman disease (also known as sinus histiocytosis with massive lymphadenopathy) is an uncommon, idiopathic, benign histiocytic lesion. It usually involves the cervical lymph nodes and, less commonly, extranodal sites. Involvement of the breast is rare, with only 17 cases reported in the English literature to date. Here we describe 3 new patients with extranodal Rosai-Dorfman disease in the breast. All 3 patients-aged 45, 53, and 54 years-presented with solid breast lesions that were detected on screening mammography and had no clinical history of Rosai-Dorfman disease or radiographic evidence of extramammary involvement. Initial diagnoses were accomplished by needle core biopsy in the one case and excisional biopsy in the other two. We present the histopathologic findings and follow-up of each patient and conduct a literature review of mammary Rosai-Dorfman disease with emphasis on its differential diagnosis. Because Rosai-Dorfman disease frequently mimics invasive breast carcinoma in its clinical presentation and radiographic appearance-and can mimic other benign or malignant histiocytic lesions microscopically-awareness and appropriate diagnosis of this entity are essential for proper treatment.

Coexpression of alpha6beta4 integrin and guanine nucleotide exchange factor Net1 identifies node-positive breast cancer patients at high risk for distant metastasis.

Preclinical data indicate that alpha6beta4 integrin signaling through Ras homolog gene family, member A, plays an important role in tumor cell motility. The objective of this study was to determine whether the combined expression of alpha6beta4 integrin and neuroepithelioma transforming gene 1 (Net1), a guanine nucleotide exchange factor specific for Ras homolog gene family member A, is associated with adverse clinical outcome in breast cancer patients. Immunohistochemical expression of each protein was evaluated in a tumor tissue microarray prepared from the primary tumors of 94 node-positive patients with invasive breast carcinoma treated with total mastectomy and doxorubicin-based chemotherapy without radiation with a median follow-up of 12.5 years. Associations between staining results and multiple clinicopathologic variables were investigated. Although there was no significant association between alpha6beta4 integrin or Net1 expression and clinical outcome when each marker was considered individually, coexpression of alpha6beta4 and Net1 was associated with decreased distant metastasis-free survival (P = 0.030). In the subset of patients with hormone receptor-positive tumors, coexpression of alpha6beta4 and Net1 was associated with a decrease in distant metastasis-free and overall survival (P < 0.001 and P = 0.006, respectively). Although an association between human epidermal growth factor receptor 2 expression and coexpression of alpha6beta4 and Net1 (P = 0.008) was observed, coexpression of alpha6beta4 and Net1 (hazard ratio, 1.63; P = 0.02) and lymphovascular invasion (hazard ratio, 2.35; P = 0.02) were the only factors independently associated with the development of distant metastasis in multivariate analysis. These findings suggest that coexpression of alpha6beta4 integrin and Net1 could be a useful biomarker for aggressive disease in node-positive breast cancer patients.

Invasive micropapillary carcinoma of the breast: mammographic, sonographic, and MRI features.

OBJECTIVE: The purpose of this study was to describe the clinical, imaging, and histopathologic findings of invasive micropapillary carcinoma of the breast. CONCLUSION: The imaging characteristics of invasive micropapillary carcinoma are highly suggestive of malignancy. The lesion is a high-density irregular mass with indistinct margins associated with microcalcifications on mammograms; a solid irregular hypoechoic mass with indistinct margins and frequent axillary nodal involvement on sonograms; and a multifocal mass on MR images. This tumor may necessitate aggressive management.

Primary peritoneal serous carcinoma presenting as inflammatory breast cancer.

Metastasis to the breast from extramammary malignancies is rare. Nevertheless, its recognition is important because the prognosis and treatment differ from that of primary breast cancer. We report a unique case of primary peritoneal serous carcinoma that initially presented as inflammatory breast cancer. The patient received neoadjuvant chemotherapy for breast cancer and subsequently underwent bilateral total mastectomy and bilateral sentinel lymph node biopsy. She was found to have extensive intralymphatic carcinoma in both breasts, with only focal minimal breast parenchymal involvement, and residual metastatic carcinoma in bilateral sentinel lymph nodes. Further work-up revealed pelvic ascites and omental nodularities. The patient underwent laparoscopic bilateral salpingo-oophorectomy, which revealed high-grade serous carcinoma involving both ovaries and fallopian tubes. Molecular testing of tumor from the ovary and axillary lymph node showed an identical pattern of allelic loss, confirming a common origin for both tumors. To our knowledge, this is the first reported case of an extramammary primary malignancy that not only presented as inflammatory breast cancer but also was diagnosed and initially treated as such.

Fibroepithelial lesions of the breast with pleomorphic stromal giant cells: a clinicopathologic study of 4 cases and review of the literature.

Pleomorphic stromal giant cells are occasionally found as an incidental finding in breast tissue but are only rarely seen in fibroepithelial lesions. In this report, we describe 4 fibroadenoma-like lesions of the breast with pleomorphic stromal giant cells. Two cases had focal stromal hypercellularity, one of which was with architectural features borderline between a fibroadenoma and a phyllodes tumor, but none was considered diagnostic of phyllodes tumor. One lesion had up to 4 mitotic figures per 10 high-power fields, including rare atypical mitotic figures. The remaining 3 cases lacked mitotic activity. Follow-up for 3 cases at 16 to 59 months revealed no evidence of tumor recurrence. The fourth case was lost to follow-up. It appears that the presence of pleomorphic stromal giant cells in an otherwise benign fibroepithelial lesion has no adverse clinical significance. The clinicopathologic features of each case are discussed, and a review of the literature is provided.