Periductal stromal tumour of the breast

Definition

A rare biphasic tumour of the breast characterised by a proliferation of sarcomatous spindle cells surrounding rounded tubules and infiltrating the surrounding adipose tissue. It is distinguished from both fibroadenoma and phyllodes tumour by the lack of any foliated (leaf-like) architecture (hypercellular stroma around distorted epithelial/myoepithelial lined spaces).

Epidemiology

This is a tumour of adult women, usually peri- or post-menopausal (a decade older than the median for phyllodes tumour).

Macroscopic appearances

• Periductal stromal sarcoma: usually forms an ill-defined white/grey/tan/yellow mass. There may be scattered minute cysts. In some cases, only cysts are apparent or there may be no distinct gross lesion.

Histopathology

• Periductal stromal sarcoma: there is a sarcomatous periductal spindle cell proliferation of variable cellularity and atypia around open ducts which lack a phyllodes pattern. There are usually multiple nodules, often separated by fat, within infiltration of tumour into the fat. Where there is extension into lobules, the lobular architecture is preserved. The mitotic rate is greater than 3 per 10 HPF.

• Periductal stromal hyperplasia: the periductal stromal proliferation is bland, with no, or minimal, atypia. The mitotic rate is 0-2 per 10 HPF. Some cases may be associated with fibrocystic changes or atypical ductal hyperplasia (DIN 1c).

Immunohistochemistry of the stromal / sarcomatous component

Differential diagnosis

• fibroadenomatoid hyperplasia

• myxoid fibroadenoma

• phyllodes tumour

• low grade sarcoma, NOS: these generally displace mammary tissue.

• fibromatosis

• pseudoangiomatous hyperplasia

Prognosis

• Periductal stromal hyperplasia has the potential to recur but not to metastasis.

• Periductal stromal sarcoma is a low grade malignancy. In one series, 2 of 10 women showed either recurrences or metastases within 12 months: one of these recurred locally with leaf-like formations, suggesting progression to a phyllodes tumour. The other had lung metastases, presumably from an angiosarcomatous component.

References

1 Burga, A.M. and Tavassoli, F.A. Periductal stromal tumor: a rare lesion with low-grade sarcomatous behavior. Am J Surg Pathol 2003;27:343-8.

2Chen, C.M., Chen, C.J., Chang, C.L., Shyu, J.S., Hsieh, H.F. and Harn, H.J. CD34, CD117, and actin expression in phyllodes tumor of the breast. J Surg Res 2000;94:84-91.

This page last revised 19.3.2003.

©SMUHT/PW Bishop