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Breast Imaging

E2838. Spindle Cell Lesions of the Breast: The Good, the Bad and the Ugly

Weiss A,  Clark E,  Sheth M,  Gupta E. Northwell Health, Manhasset, NY

Address correspondence to E. Clark (eclark12@nshs.edu)

Background Information: Spindle cell lesions of the breast are uncommon and include a wide variety of different entities from benign and reactive to aggressive and malignant. The morphologic and imaging features of some of the lesions overlap, creating a significant diagnostic challenge. This is particularly true when the lesion is sampled by core needle biopsy and not completely surgically excised. Correct identification of these lesions is very important because the prognosis, biological behavior, and treatment are often quite different. The purpose of our exhibit is to familiarize radiologists with the diverse imaging appearances of several rare spindle cell lesions seen at our institution while presenting a way of organizing these lesions into subcategories, making them easier to remember and diagnose.

Educational Goals/Teaching Points: Our goal is to review the spectrum of major spindle cell lesions of the breast and present their variable imaging features. The combination of clinical history and imaging features can provide helpful clues to narrow the differential diagnosis and establish the correct diagnosis. Teaching points are as follows. Distinguishing between a fibroadenoma and benign phyllodes tumor (PT) is challenging on core needle biopsy when there is increased stromal cellularity. Imaging features of a mass with clefts or round cysts on ultrasound is suggestive of PT. When a malignant spindle cell lesion is diagnosed on core biopsy, the differential diagnosis includes metaplastic carcinoma, malignant PT, and sarcoma. The diagnosis of primary breast sarcoma is exceedingly rare and it should never be made before excluding these other entities. Some spindle cell carcinomas may be deceptively bland and may resemble fibromatosis or a scar on imaging. Therefore, any suspicious changes on follow-up imaging should be carefully examined. As a group, spindle cell carcinomas have a poorer prognosis than conventional invasive breast cancers and are less frequently associated with axillary lymph node metastases. Nodular fasciitis, although benign, requires surgical excision for definitive diagnosis, as it can mimic malignancy on clinical examination, imaging, and histology.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques: Spindle cell lesions are composed of two main cell types: mesenchymal and epithelial. They are categorized into monophasic and biphasic variants if the mesenchymal (monophasic) or both components (biphasic) predominate. The monophasic lesions are divided into pure pleomorphic and bland spindle cells and biphasic lesions are composed of spindle cells with either a benign or malignant epithelial component. We will present imaging examples of tumors in each of these categories along with a discussion of the clinical presentation, imaging features, treatment, and prognosis.

Conclusion: Spindle cell lesions of the breast are a diverse group that sometimes presents a diagnostic challenge. Knowing the spectrum of radiologic appearances in combination with clinical history allows the radiologist to narrow the differential diagnosis. Some spindle cell lesions diagnosed on core biopsy require careful multidisciplinary discussion regarding their management.