Rosai-Dorfman disease of the breast

Case contributed by Gerard Carbo
Diagnosis certain


50-year-old man, consulting after feeling a lump in his right breast (it appeared about 4-5 months ago).

Patient Data

Age: 50 years
Gender: Male

Digital breast mammography study (CC and MLO projections) revealed a dense mass lesion with irregular / indistinct margins in the upper outer quadrant of the right breast corresponding to the palpable lump (index lesion). 

Also in the right breast, a subtle small nodular lesion was found at inner quadrant (barely noticeable in this image). 

A third incidental lesion was found at left breast, located in the union of upper quadrants, corresponding to an oval and circumscribed nodule.


The larger right breast lesion corresponding to the palpable lump was a solid hypoechoic mass with partially circumscribed margins located at upper outer quadrant (UOQ) of right breast. Targeted ultrasound showed a 2.4 cm lobulated, hypoechoic mass with indistinct margins and increased vascularity. Also, notice the radial hypoechoic projections protruding from the lesion surrounded by increased locoregional fat echogenicity (probably related to edema or local inflammatory changes). 

Also in the right breast, an alternative lesion was found at upper inner quadrant (UIQ), corresponding to an 8 mm hypoechoic nodule with irregular margins and some surrounding echogenic fat halo (characteristics similar to the previous one). 

A third incidental lesion was found at left breast, located anteriorly in the 12 o’clock axis, corresponding to a 7 mm circumscribed hypoechoic oval nodule on ultrasound (low suspicion features).

No abnormal lymph nodes were identified in both axillary regions.

Right breast lesions were categorized as BIRADS 4C (palpable index lesion) and 4B (8 mm nodule) and ultrasound-guided biopsies were performed on the same day. Fourteen gauge core biopsy devices were used to obtain core specimens. Left breast lesion was categorized as BIRADS 3 but, in patient's clinical context, a delayed US-guided biopsy was performed one week later. 


Low-power slide of core biopsy specimen, measured with a Leica DMD 108 microscope, showed large pale histiocytes that are positive for the S100 protein, with lymphocytes within the cytoplasm of enlarged histiocytes indicating lymphophagocytosis, also known as emperipolesis, a feature typical of Rosai-Dorfman disease.

Case Discussion

Rosai-Dorfman disease of the breast is a rare benign inflammatory disorder that can mimic breast cancer clinically and on imaging studies. Both men and women may present with a palpable lump or tenderness and can have either a single lesion or multiple lesions. Strong staining of histiocytes with S100 is characteristic of Rosai-Dorfman. Although nonspecific, emperipolesis is also characteristic and supports the diagnosis when present. Early pathologic diagnosis of Rosai-Dorfman disease of the breast is key because the disease can be treated conservatively

Typical breast imaging findings are classified as suspicious or highly suspicious for malignancy, and breast involvement less commonly mimics fibrocystic disease or fibroadenoma.

  • Mammography may show a high-density lobulated mass with a partially circumscribed or ill-defined margin. Nodules can be large and can infiltrate the breast parenchyma. Small diffuse breast nodules have also been reported.

  • On breast US, the mass appears hypoechoic with indistinct or angulated margins and shows increased vascularity on color Doppler imaging. Often, it can be associated to diffuse radial hypoechoic projections protruding from the lesion surrounded by an echogenic fat halo suggesting malignancy (it's related to edema or local inflammatory changes). 

Acknowledgments to Dra Cristina Meléndez Muñoz for contributing with the microscopic images.

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