Reporting a rare case of pleomorphic adenoma of the breast

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.

Benign mixed tumour of the breast and breast skin, two cases with diagnostic difficulties

We present two cases of pleomorphic adenoma, one that developed in the breast parenchyma and the other in the breast skin, with their histopathological differential diagnosis.

Pleomorphic adenoma of breast: a radiological and pathological study of a common tumor in an uncommon location

Pleomorphic adenoma occurs commonly in the major salivary glands but is uncommonly encountered in the breast. In both of these locations, the tumor is typically grossly circumscribed and has a “mixed” histological appearance, being composed of myoepithelial and epithelial components amid a myxochondroid matrix. Herein, we report a case of pleomorphic adenoma of the breast which was preoperatively thought to represent a fibroadenoma on clinical and radiological grounds. It is the rarity of the tumor in the breast, rather than its histological appearance, that causes diagnostic difficulty.