A case report of fibroadenoma of the breast with characteristic cystic change on a cut surface

Background

Fibroadenoma of the breast is a well-circumscribed benign tumor with epithelial and stromal growth. It usually occurs in young women, with an incidence of 18.5%,^1,2 except for complex fibroadenoma, which is an unusual variant of fibroadenoma occurring in elderly women. ³ Although cystic changes are sometimes present, fibroadenoma with predominant cystic change is very unusual,^3–5 and the interpretation of the lesion seems to be unclear. While the exact incidence of the lesion is unclear, in 2015, Bhat et al. ³ reported that only one case had been described thus far. When the tumor is obviously cystic, it resembles an intraductal papilloma.^4,6 Some papers have stated that fibroadenoma with remarkable cystic change is called cystic fibroadenoma and classified under complex fibroadenoma.^3,5,7 There are also a few reports describing benign fibroepithelial lesions with cystic features and intracystic or intraductal components as intraductal fibroadenoma or intraductal fibroadenomatosis.^2,8,9 Most previous reports have focused on the microscopic view of these lesions.

We herein report an unusual case of fibroadenoma with remarkable cystic change and intracystic growth showing a characteristic macroscopic view.

Case presentation

A 43-year-old woman presented herself to a medical doctor’s office due to a rapidly growing tumor of the right breast. Ultrasonography revealed a middle- to high-echoic mass. A core needle biopsy was performed showing hypocellular myxoid stroma with small spindle cells and mammary ducts without atypia (Figure 1(a)). Based on the core needle biopsy findings, a benign lesion, such as phyllodes tumor or fibroadenoma, was suspected, and the tumor was surgically resected about 2 weeks after the biopsy. On a macroscopic study, the cut surface of the tumor revealed a remarkably cystic and well-circumscribed lesion with an intracystic polypoid component, measuring 4.0 × 3.0 cm² in diameter with a whitish to tan color and hemorrhage (Figure 1(b)). Microscopically, a variety of findings of epithelial and stromal proliferation, such as a pericanalicular pattern, an intracanalicular pattern, and a polypoid or leaf-like structure with stromal growth, and proliferation of small tubular structures were observed (Figure 1(c) and (d)). The stromal component had mild to moderate cellularity, showing myxoid change in some areas. The mitotic activity was low. Infarction and hemorrhage were also observed, but there were no findings of malignancy.

OPEN IN VIEWER

Figure 1.

Microscopic findings of the biopsy specimen and macroscopic and microscopic findings of the surgical specimen. (a) In the biopsy specimen, myxoid stroma with low cellularity and mammary ducts without atypia were observed. (b) The cut surface of the surgical specimen revealed a remarkably cystic and well-circumscribed lesion with an intracystic polypoid component, measuring 4.0 × 3.0 cm² in diameter with a whitish to tan color and hemorrhage. (c) and (d) On a microscopic study of the surgical specimen, the intracystic component showed a variety of findings of epithelial and stromal proliferation. (c) A pericanalicular pattern, an intracanalicular pattern, and a leaf-like structure with stromal growth, and (d) proliferation of small tubular structures were observed. (a) Bar = 200 μm (H&E staining; original magnification: ×100). (c) and (d) Bar = 1.0 mm (H&E staining; original magnification: ×12.5).

Although phyllodes tumor was considered as a differential diagnosis, she was ultimately diagnosed with fibroadenoma (intraductal fibroadenoma) based on these findings.

Discussion

The most unique point of this case is the remarkable cystic change in the tumor; however, the cyst was filled with intracystic polypoid component. Retrospectively, the mass with middle to high echo intensity on ultrasonography was likely the intracystic component, and the cystic change in the lesion might be unremarkable.

One of the differential diagnoses of an intracystic mass is a phyllodes tumor. It can be difficult to distinguish fibroadenoma with an intracanalicular pattern from phyllodes tumor. ⁸ In the present case, the microscopic study revealed an intracanalicular pattern or a leaf-like structure with stromal growth; however, the lesion showed not only interstitial growth but also growth of the epithelial component, which led to the diagnosis of fibroadenoma. This is because fibroadenoma is characterized by biphasic proliferation of epithelial and stromal components; on the other hand, phyllodes tumor mainly shows stromal growth. ¹ While carcinoma was another differential diagnosis, as the tumor had shown rapid growth, there were no malignant findings microscopically. No second opinion was obtained in this case.

Conclusion

This case is interesting not only because fibroadenoma with remarkable cystic change is unusual but also because the breast tumor showed a characteristically cystic appearance on its macroscopic view. Opinions differ as to the interpretation of fibroadenoma with prominent cystic change, and another fibroepithelial lesion may be one of differential diagnoses, so further investigations will be required to better understand this entity.