Pleomorphic adenoma of breast-a case report and review of literature

Salivary Gland-like Tumors of the Breast

CONTEXT

The World Health Organization classification of tumors of the breast recognizes several special type carcinomas and benign lesions with features comparable to those of salivary gland tumors.

OBJECTIVE

To discuss the histologic, immunophenotypic, molecular, and clinical features of salivary gland-like carcinomas of the breast. These breast tumors are often negative for hormone receptors and human epidermal growth factor receptor 2 (HER2), that is, triple-negative, but they generally have a much better prognosis than triple-negative breast carcinomas of no special type. We compare the immunophenotypic, molecular, and clinical features of these breast tumors with their salivary gland counterparts, highlighting similarities and differences. We also discuss benign salivary gland-like breast tumors. Finally, we highlight recent developments in understanding the molecular pathogenesis of these breast tumors and novel ancillary studies that can be used to support their diagnosis.

DATA SOURCES

A literature review was conducted, and papers were selected for further analysis and discussion by the authors of this review based on their novelty, applicability, and impact in the field.

CONCLUSIONS

Breast tumors that exhibit morphologic overlap with salivary gland tumors have been recognized by pathologists for decades, but the similarities and differences in their molecular pathogenesis have not been understood until more recently. These developments have led to novel diagnostic tools and further knowledge of these rare breast lesions.

Pleomorphic Adenoma of the Breast: A Rare Benign Lesion Masquerading as a Metaplastic Breast Carcinoma on Core-Needle Biopsy

We report a rare case of pleomorphic adenoma (benign mixed tumor) of the breast in a 66-year-old female. A 5.5 cm hypoechoic mass with lobulated margins was noted on ultrasound. A biopsy showed an atypical cartilaginous lesion, leading to a subsequent segmental mastectomy, which was initially interpreted as metaplastic breast carcinoma. On the second review at our tertiary care center, a diagnosis of a pleomorphic adenoma was favored due to the circumscription and the benign epithelial component. Due to unfamiliarity with this entity, this neoplasm has occasionally been misdiagnosed clinically and even been overcalled on core needle biopsies. Careful clinical, radiological, and pathological correlation is required to avoid unnecessarily aggressive surgery, and a differential diagnosis of pleomorphic adenoma must be included in cases of well-demarcated breast masses showing myxoid or cartilaginous changes on core-needle biopsy.

Pleomorphic adenoma of the breast with cytologic atypia on cytopathology: A potential diagnostic pitfall and literature review

Pleomorphic adenoma of the salivary gland is a well-established and recognized diagnosis; however, pleomorphic adenomas of the breast are rare and can be difficult to diagnose on cytology or intraoperatively. We report a case that was misdiagnosed on a fine needle aspiration and frozen section. The pitfalls, differential diagnoses, and current management are discussed.

Some Pleomorphic Adenomas of the Breast Share PLAG1 Rearrangements with the Analogous Tumor of the Salivary Glands

AIMS

Pleomorphic adenoma (PA) of the breast, and especially its malignant transformation, is extremely rare and represents a diagnostic pitfall. Molecular alterations in this entity have not been investigated. We aimed to examine the clinicopathologic features of our breast PAs and perform molecular analysis.

METHODS

Seven cases of breast PA including two cases of carcinoma ex PA were analyzed. PLAG1 and HMGA2 gene rearrangements were assayed by FISH and RNA-Seq, respectively. RT-PCR and Sanger sequencing were used to verify RNA sequencing results.

RESULTS

All seven cases of breast PA occurred in women. The histological features were similar to the analogous tumor in salivary glands, including a dual epithelial-myoepithelial component and negativity of ER, PR, and HER2 by immunohistochemistry. Of the two cases with carcinoma ex PA, one demonstrated minimal invasion and one was extensively invasive. PLAG1 rearrangements were identified in two cases (28.6%), but no rearrangements of HMG2A were found. A novel fusion product in PAs, TRPS1-PLAG1, was identified in one case. No patients had recurrence or metastasis with a follow-up period of 6 to 158 months.

CONCLUSIONS

Breast PA is rare, but it is an important differential diagnosis of breast pathology with the potential to develop carcinoma ex PA. We reported a novel TRPS1-PLAG1 fusion gene in breast PA.

A Comparative Review of Mixed Mammary Tumors in Mammals

Mixed tumors are characterized by the histological identification of two or more cell types. Commonly, a mixture of epithelial and myoepithelial cells is included in abundant stroma, which can consist of myxoid, chondroid or bony matrices. Spontaneously arising mixed tumors are rare lesions in the human breast but are common in human salivary glands and canine mammary glands. Subtle histopathological characteristics and overlapping attributes of malignant lesions with other benign lesions can lead to a diagnostic challenge. Mixed tumors can present as benign or malignant. While malignant mixed tumors are quite rare in the human breast they have a poor prognosis. Benign mixed mammary tumors occur more frequently in female dogs than in humans and are usually associated with a good prognosis. This review will provide a comprehensive overview of mixed mammary tumors, across various mammalian species.

A rare benign tumor of breast masquerading on fine needle aspiration cytology: A case report

Pleomorphic adenoma is a common tumor encountered in major salivary gland and very rarely seen in breast. This matrix producing tumor can be confused with fibroadenoma, phyllodes tumor and metaplastic carcinoma on fine needle aspiration cytology(FNAC). Pre-operative diagnosis of pleomorphic adenoma helps in preventing surgical over or under treatment of the disease. We present an extremely rare case of pleomorphic adenoma of breast diagnosed on FNAC with histopathological confirmation.

Breast lesions of uncertain malignant nature and limited metastatic potential: proposals to improve their recognition and clinical management

Breast lesions comprise a family of heterogeneous entities with variable patterns of presentation, morphology and clinical behaviour. The majority of breast lesions are classified traditionally into benign and malignant conditions and their behaviour can, in the vast majority of cases, be predicted with a reasonable degree of accuracy. However, there remain lesions which show borderline features and lie in a grey zone between benign and malignant, as their behaviour cannot be predicted reliably. Defined pathological categorization of such lesions is challenging, and for some entities is recognized to be subjective and include a range of diagnoses, and forms of terminology, which may trigger over- or undertreatment. The rarity of these lesions makes the acquisition of clinical evidence problematic and limits the development of a sufficient evidence base to support informed decision-making by clinicians and patients. Emerging molecular evidence is providing a greater understanding of the biology of these lesions, but this may or may not be reflected in their clinical behaviour. Herein we discuss some breast lesions that are associated with uncertainty regarding classification and behaviour, and hence management. These include biologically invasive malignant lesions associated with uncertain metastatic potential, such as low-grade adenosquamous carcinoma, low-grade fibromatosis-like spindle cell carcinoma and encapsulated papillary carcinoma. Other lesions of uncertain malignant nature remain, such as mammary cylindroma, atypical microglandular adenosis, mammary pleomorphic adenoma and infiltrating epitheliosis. The concept of categories of (1) breast lesions of uncertain malignant nature and (2) breast lesions of limited metastatic potential are proposed with details of which histological entities could be included in each category, and their management implications are discussed.