Mass Shape — Oval
Oval is a mass shape descriptor indicating an elliptical or egg-shaped mass with one axis longer than the other two and no undulations.
Definition
A mass that is elliptical or egg-shaped with one axis longer than the other two and no undulations (smooth contour without indentations).
Key Feature
- No undulations distinguishes oval from lobulated
- An oval mass may have 2–3 gentle lobulations in the prior (5th edition) lexicon, but in v2025 any undulation places the mass in the lobulated category
v2025 Update
In the 5th Edition Atlas (2013), masses with a few gentle lobulations were included within the oval shape category. In v2025, lobulated is reintroduced as a separate shape descriptor, so a truly oval mass must have NO undulations.
Imaging Appearance
- Well-defined elliptical or egg-shaped contour
- Smooth, uninterrupted border without protrusions or indentations
- One diameter (long axis) clearly longer than the others
Differential Diagnosis
Oval masses are most commonly benign:
- Fibroadenoma — classic benign oval mass
- Simple cyst — oval or round, circumscribed, no enhancement
- Lymph node — oval with fatty hilum
- Papilloma — can be oval, often intraductal
- Mucinous carcinoma — can be oval and T2 hyperintense; malignant exception
Board Pearl
Oval shape is one of four benign-favoring features. Combined with circumscribed margin + homogeneous enhancement (or dark internal septations) + T2 hyperintensity, the mass has ≤ 2% malignancy risk.
Pitfalls
- An oval mass can still be malignant (e.g., oval, indistinct IDC)
- Do not equate oval shape alone with benignity — always consider the full constellation of features
- Oval + circumscribed + T2 hyperintense + homogeneous: fibroadenoma-like features → ≤ 2% cancer likelihood