How are Phyllodes Tumors Diagnosed?

Phyllodes tumors (PTs) are fibroepithelial tumors of the breast. These are rare, presenting clinically as painless lumps. They are primarily found in women between the fourth and sixth decades of life, with a peak incidence at the age of 45. Their occurrence in men is extremely rare, but has been reported in cases associated with enlargement of the male breast due to hormonal imbalances.

The rarity of PTs makes them somewhat difficult to diagnose, especially in the case of doctors who do not encounter them often. This difficulty is compounded by the similarity in the physical characteristics of PTs and fibroadenomas. Fibroadenomas are benign breast tumors that consist of normal breast tissue, and are frequently seen in younger women. However, PTs can be distinguished from fibroadenomas by their appearance later on in life and by their rapid growth.

Steps in the diagnosis of a PT include:

  • physical examination to detect lumps,
  • imaging tests such as mammograms, ultrasound and MRI,
  • and biopsy.

Radiologic diagnostic tools

The mainstays of routine breast investigations are mammography and ultrasound (US) examination of the tumor. On radiologic examination, PTs tend to have a lobulated shape with a heterogeneous composition and well-defined borders, as opposed to fibroadenomas. US features include well-demarcated smooth margins that are echogenic, with homogenous internal echoes. Microcalcifications are absent, and the PTs sometimes have some cystic changes within them. Signs that would be consistent with malignant PTs include poorly defined tumor margins, hypo-echogenicity, and posterior acoustic shadowing.

PTs on a mammogram appear as large oval or round masses with well-defined borders. Although rare, coarse calcifications may be observed. Compression of the surrounding tissue may lead to the formation of a radiolucent halo around the lesion.

MRI is used to obtain additional images of PTs and to assist in planning for surgery. On MRI, PTs appear lobulated or round with well-defined margins, and a heterogeneous internal structure.  

Cytological examination

Samples of the tumor may be taken for microscopic examination, because biopsy is the only way to accurately tell if the lesions are PTs. A fine needle aspiration biopsy is controversial in its ability to distinguish malignant PTs from benign ones, in contrast to making a differentiation between benign PTs from fibroadenomas. On biopsy, the presence of stromal and epithelial components is supportive of a diagnosis of PT. It should be noted, however, that malignant PTs may be devoid of epithelial cells.

In order to conduct cytological exams, biopsies are required. In addition to or instead of fine needle aspiration, these may be done by core needle biopsy. Here samples are taken from the tumor via a special needle. Sometimes biopsies may be done as excisional procedures, where the entire tumor is removed. Some doctors feel that the latter is a better choice, since smaller samples may not be adequate to confirm PTs.

Microscopic examination of PTs results in their classification as malignant, borderline or benign. Malignant tumors have poorly defined edges with abnormally shaped stromal cells that are rapidly dividing. Epithelial cells which normally line the lobules and ducts may or may not be seen. In contrast, benign PTs tend to have well-defined edges with cells that are not dividing as rapidly. Their stromal cells have an almost normal appearance and epithelial cells are present. Borderline PTs, as one would expect, have characteristics that tend to fall in a grey zone between benign and malignant PTs.

On a macroscopic basis, small PTs usually have a lobulated surface with a uniformly white appearance and soft solid consistency. They are fairly similar in appearance to fibroadenomas. Cutting these tumors reveals a hemorrhagic and fibro-gelatinous consistency, with areas of cell death and characteristic “leaf-like” protrusions into cystic spaces. This “leaf-like” appearance is the origin of the name phyllodes, which means “leaf-like” in the Greek language.


Further Reading

Last Updated: Dec 30, 2022

Dr. Damien Jonas Wilson

Written by

Dr. Damien Jonas Wilson

Dr. Damien Jonas Wilson is a medical doctor from St. Martin in the Caribbean. He was awarded his Medical Degree (MD) from the University of Zagreb Teaching Hospital. His training in general medicine and surgery compliments his degree in biomolecular engineering (BASc.Eng.) from Utrecht, the Netherlands. During this degree, he completed a dissertation in the field of oncology at the Harvard Medical School/ Massachusetts General Hospital. Dr. Wilson currently works in the UK as a medical practitioner.


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