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

The Genetic Landscape of Fibroepithelial Lesions of the Breast

Fibroepithelial lesions of the breast encompass a broad spectrum of lesions from fibroadenomas and their variants to phyllodes tumors, including their clinical range of benign, borderline, and malignant. Classification of this spectrum of neoplasms has historically and currently been based purely on morphology, although the nomenclature has shifted over the years largely due to the significant histologic overlap that exists primarily within the cellular fibroadenomas to borderline malignant phyllodes tumor categories. A review of the current diagnostic challenge, proposed ancillary studied and their value in prognostic significance, is provided. This article highlights the most recent molecular and genetic findings as well as the limitations of the studies, in the context of practical and available applications for the diagnostician and managerial implications for the clinician.

Fibroepithelial Lesions of the Breast: Update on Molecular Profile With Focus on Pediatric Population

CONTEXT.—

This review article derives from the breast pathology lecture at the Eighth Princeton Integrated Pathology Symposium (PIPS VIII).

OBJECTIVE.—

To provide a literature review and update on fibroepithelial lesions of the breast with molecular findings and findings regarding the pediatric population.

DATA SOURCES.—

The sources include extensive literature review, personal research, and experience.

CONCLUSIONS.—

Given significant differences in prognosis and management of fibroepithelial lesions, we aim to provide readers with pertinent definitions, pathomorphology, molecular findings, and management for each diagnosis, with insights on the pediatric population.

A Diagnostic Approach to Fibroepithelial Breast Lesions

Fibroepithelial breast lesions encompass a heterogeneous group of neoplasms that range from benign to malignant, each exhibiting differing degrees of stromal proliferation in relation to the epithelial compartment. Fibroadenomas are common benign neoplasms that may be treated conservatively. Phyllodes tumors are relatively rare lesions, and classified as benign, borderline, or malignant based on histologic evaluation of various parameters. The diagnostic interpretation of "gray-zone" fibroepithelial lesions often imposes formidable demands on a pathologist's skills. This article offers practical recommendations for the diagnostic workup of these lesions, including the appropriate utilization of ancillary investigations and the approach to core needle biopsies.

Fibroadenoma With Pleomorphic Stromal Giant Cells: It’s Not as Bad as It Looks!

Clinically relevant histological categorization of fibroepithelial lesions can be a daunting task, especially in a core needle biopsy. Assessment of stromal nuclear atypia, including nuclear pleomorphism and mitotic activity, is a key morphological feature employed to classify fibroepithelial lesions. We describe a case of fibroadenoma with markedly atypical nuclear features in the stromal cells that led to misclassification as phyllodes tumor in the core needle biopsy. Excision showed a fibroadenoma containing pleomorphic stromal giant cells, with occasional mitotic figures, including atypical forms. Aforementioned nuclear findings in a fibroepithelial lesion raise a legitimate question of phyllodes tumor. Knowledge of this pitfall may help avoid overtreatment of an otherwise benign fibroepithelial lesion.

Benign soft tissue lesions that may mimic malignancy

Soft tissue lesions which mimic malignancy (pseudosarcomas), represent a significant diagnostic challenge for pathologists. Many features often associated with malignancy including rapid and infiltrative growth, increased cellularity and mitotic activity, and nuclear pleomorphism are present in benign and reactive conditions. This review highlights repair reactions including nodular fasciitis, proliferative fasciitis/myositis, intravascular papillary endothelial hyperplasia, and fat necrosis; lipoma and spindle cell/pleomorphic lipoma; fibroepithelial stromal (pseudosarcomatoid) polyp; phosphaturic mesenchymal tumor; and myxoma. While not inclusive of every pseudoneoplastic soft tissue lesion, this review emphasizes important diagnostic pitfalls and stresses the value of clinical, pathologic, and radiologic correlation.

Multinucleate Giant Cells in FNAC of Benign Breast Lesions: Its Significance

BACKGROUND

Multinucleate giant cells are described in breast aspirates. However, due to its rarity very few cases have been described cytologically. Hence recognition and correct interpretation of their presence is difficult, yet crucial for accurate diagnosis.

MATERIALS AND METHODS

The prospective study of FNAC (fine needle aspirate cytology) of breast lumps was conducted for a period of six months. Direct smears were prepared from the material aspirated. In case of fluid aspirates, centrifuge done and cell sediment was used for making smears. Smears were alcohol fixed and stained with PAP/H&E or air dried smears were stained with Leishman stain. Further smears were subjected to immunocytochemistry using vimentin and CD34 markers to know the origin of multinucleate giant cells.

RESULTS

We have reported 11 cases of breast lesions, which showed multinucleate giant cells on FNAC. Out of the 11 cases, Cytologically six cases showed granuloma debris with relative proportion of epithelioid histiocytes, lymphocytes, neutrophils and multinucleate giant cells. Two cases were diagnosed as acute suppurative granulomatous mastitis. Two cases of fibroadenoma and one case of fat necrosis showed multinucleate giant cells. Immunocytochemistry showed vimentin positivity in both stromal and histiocytic type of multinucleate giant cells and in isolated histiocytes. CD34 was focally positive in histiocytic type of giant cells.

CONCLUSION

An effort is made to distinguish between the stromal and histiocytic type giant cells in non-neoplastic breast lesions. Further molecular studies have to be done to know the exact histogenesis and role of these multinucleate giant cells in benign lesions.

Fibroepithelial tumors of the breast: pathologic and immunohistochemical features and molecular mechanisms

CONTEXT

The 2 main prototypes of fibroepithelial tumors of the breast include fibroadenoma and phyllodes tumor (PT). Although both tumors share some overlapping histologic features, there are significant differences in their clinical behavior and management. Phyllodes tumors have been further divided into clinically relevant subtypes, and there is more than one classification scheme for PT currently in use, suggesting a lack of consistency within different practices. Accurate differentiation between fibroadenoma and PT, as well as the grading of PT, may sometimes be challenging on preoperative core needle biopsy. Some immunohistochemical markers have been suggested to aid in the pathologic classification of these lesions.

OBJECTIVE

To discuss the salient histopathologic features of fibroepithelial tumors and review the molecular pathways proposed for the initiation, progression, and metastasis of PTs. Also, to provide an update on immunohistochemical markers that may be useful in their differential diagnosis and outline the practice and experience at our institution from a pathologic perspective.

DATA SOURCES

Sources included published articles from peer-reviewed journals in PubMed (US National Library of Medicine).

CONCLUSIONS

Fibroepithelial tumor of the breast is a heterogenous group of lesions ranging from fibroadenoma at the benign end of the spectrum to malignant PT. There are overlapping histologic features among various subtypes, and transformation and progression to a more malignant phenotype may also occur. Given the significant clinical differences within various subtypes, accurate pathologic classification is important for appropriate management. Although some immunohistochemical markers may be useful in this differential diagnosis, histomorphology still remains the gold standard.