How to Recognise Classic "Aunt Minnie" Diagnoses for the FRCR Part 2A

What on earth is an "Aunt Minnie"?

The phrase comes from an old teaching idea. If you saw your Aunt Minnie walking down the street, you would know it was her instantly. You would not need to check her passport or measure her nose. You just know.

Radiology has the same thing. Some appearances are so specific that once you have seen them, the diagnosis is obvious. You do not reason your way there step by step. You recognise it in a heartbeat.

For the FRCR Part 2A, this matters. The exam is single best answer, and a good chunk of questions describe a classic picture and ask you to name it. If you know your Aunt Minnies, those become free marks. Quick, confident and correct.

Why they are gold in a single best answer exam

The Part 2A rewards pattern recognition. You are not scanning real images in most of the exam, you are reading a stem that describes findings. Whoever wrote the question has usually chosen a classic description on purpose.

So when a stem says "soap bubble" or "onion skin" or "light bulb", it is practically handing you the answer. The trick is having the association drilled so deeply that you barely have to think.

That frees up time and mental energy for the harder, reasoning-heavy questions later in the paper. Bank the easy ones fast.

A starter list worth memorising

Here are some of the most loved Aunt Minnies that turn up again and again. Learn the buzzword, then learn the diagnosis behind it.

• Codman triangle and sunburst periosteal reaction: osteosarcoma.
• Onion skin periosteal reaction: Ewing sarcoma (though think again if the stem is atypical).
• Soap bubble lytic lesion in the epiphysis of a young adult: giant cell tumour.
• Ground glass expansile bone lesion, no periosteal reaction: fibrous dysplasia.
• Popcorn calcification in a lung nodule: hamartoma.
• Light bulb sign on shoulder radiograph: posterior shoulder dislocation.
• String of beads on small bowel: mechanical small bowel obstruction.
• Coffee bean sign: sigmoid volvulus.
• Bird beak on barium swallow: achalasia.
• Rat tail or apple core lesion in colon: annular carcinoma.
• Double bubble in a neonate: duodenal atresia.
• Molar tooth sign on brain MRI: Joubert syndrome.
• Empty delta sign on CT venogram: dural venous sinus thrombosis.
• Dawson fingers on brain MRI: multiple sclerosis.
• Tram track calcification along the cortex: Sturge Weber syndrome.
• Whirlpool sign: midgut volvulus or ovarian torsion depending on context.

Do not just read these. Say the sign out loud, then say the diagnosis. Cover one column and test yourself. Recognition needs repetition.

The trap of the pure Aunt Minnie question

Here is where trainees lose marks. The examiners know you know the buzzwords, so they sometimes add a twist.

A stem might describe an onion skin appearance but then give an age of sixty and a history of pain worse at night. Now you should be thinking osteomyelitis or something else, not just reflexively answering Ewing sarcoma.

So treat the classic sign as a strong lead, not a locked answer. Read the whole stem. Check the age, the location, the clinical history and any lab values. If everything fits the classic picture, commit fast. If something jars, slow down and reconsider.

Most of the time the Aunt Minnie is genuinely the answer. But that occasional twist is exactly what separates a pass from a comfortable pass.

How to actually learn them

Reading a list once does very little. You need active recall and spaced repetition. A few practical tips.

Build your own two column sheet

Sign on the left, diagnosis on the right. Add to it every time you meet a new one during reporting or reading. Your own list sticks far better than someone else's.

Link the sign to the reason

Understanding why an appearance happens makes it much harder to forget. A sunburst is spiculated new bone laid down along vessels as an aggressive tumour breaks through the cortex. Once you picture that, you will not confuse it with a benign lesion.

Test yourself under pressure

Recognition speed only comes from repeated exposure to exam-style questions. This is where dedicated practice pays off.

SmashRad is well suited to this. It has over 12,000 exam-style single best answer questions with full explanations and Radiopaedia links, so when you meet a classic sign you can immediately read around it. Its separate Learning mode uses bite-size recall questions that are perfect for drilling buzzword to diagnosis pairs until they are automatic. The per-module performance tracking and revision recommendations show you which body systems still trip you up, and the timed mock exams train you to spot Aunt Minnies quickly under real time pressure.

A free account gives you 40 sample questions with no card needed, which is plenty to see whether this style of practice clicks for you.

A simple routine for the exam

When a stem describes a classic appearance, run through this in your head.

1. Name the sign. What does it usually mean?
2. Does the age fit? Does the location fit?
3. Does the clinical history support it or fight against it?
4. Scan the answer options. Is the obvious one there? Is there a sneaky better fit?
5. Commit and move on. Do not overthink a textbook picture.

That takes seconds once you have practised it, and it protects you from both hesitation and the occasional trap.

The bottom line

Aunt Minnies are the low hanging fruit of the FRCR Part 2A. Build your list, understand the mechanism, and drill recognition until it is instant. Then respect the stem, because the examiners will occasionally test whether you actually read it.

Want to make these appearances second nature? Head to smashrad.com, grab your free 40 questions and start spotting Aunt Minnies at speed. Your future self in the exam hall will thank you.