The Müllerian Cyst of Hattori

Everything I’ve Learned About the Müllerian Cyst of Hattori.

Disclaimer: I am not a medical professional. The information below is based on research available online through medical journals and case reports. Always talk to your doctor for personalized medical advice.

What Is a Müllerian Cyst of Hattori?

The Müllerian cyst of Hattori is an extremely rare type of cyst that forms in the posterior mediastinum, which is the space in the chest near the spine, esophagus, and aorta. It was first described by Dr. Hattori in 2005. Since then, only a few dozen cases have been reported worldwide. Because of its rarity, most doctors have never seen one in practice.

Who Gets Them?

• Almost all reported cases have been in women, usually middle-aged or older.

• The cysts are thought to come from embryonic Müllerian tissue (the same tissues that form female reproductive organs).

• They are usually discovered accidentally during imaging for something else, since most people don’t have obvious symptoms.

How Do They Look on Scans?

Radiology reports often describe them as:

• Well-circumscribed (smooth and round/oval)

• Non-enhancing (they don’t “light up” with contrast, which is a reassuring feature)

• Attenuation higher than simple fluid (they aren’t just water — they may contain protein-rich or mucinous fluid)

• Separate from the esophagus and other nearby structures

• Sizes reported range from 1 cm to 5 cm, though most are small

On MRI, they typically show a bright signal on T2 (fluid-like) and sometimes a variable signal on T1 depending on fluid content.

Symptoms (When They Do Appear)

Most people with these cysts have no symptoms. But in rare cases, larger cysts can cause:

• Difficulty swallowing (if pressing on the esophagus)

• Chest pain or discomfort

• Cough or shortness of breath (if near the airways)

• Rarely, nerve-related symptoms if close to the vagus or recurrent laryngeal nerve

Why Are They Called “Müllerian”?

When surgeons have removed these cysts and pathologists studied them under the microscope, they found that the cyst lining often tests positive for estrogen receptor (ER), progesterone receptor (PR), and PAX8. These are markers of Müllerian origin — tissues related to the female reproductive tract. That’s what makes this cyst so unusual: it appears in the chest, not where you’d expect reproductive tissue to be.

Treatment Approaches

Because these cysts are so rare, there isn’t one “standard” treatment plan. Options depend on size, symptoms, and patient health:

• Monitoring: If the cyst is small, stable, and not causing symptoms, doctors may recommend periodic imaging.

• Surgical removal: Many case reports describe removal via thoracoscopy (VATS – video-assisted thoracoscopic surgery) or open surgery. Surgery is often done to:

  • Confirm the diagnosis (rule out other cyst types or rare malignancy)

  • Prevent growth or complications in the future

• Outcomes after surgery are usually excellent, with low risk of recurrence.

What Makes Them Important

Even though they’re considered benign, these cysts are significant because:

1. They can mimic other mediastinal masses (like duplication cysts or tumors).

2. Their rarity means doctors often don’t recognize them immediately.

3. Their location near the heart, aorta, and esophagus means any growth could eventually cause symptoms.

Final Thoughts

The Müllerian cyst of Hattori is one of the rarest findings in chest imaging. For patients like me, discovering this diagnosis can be confusing and overwhelming, because information is so limited. That’s why I’m writing about it here — to bring together the research I’ve found and present it in plain English.

If you’ve been diagnosed with a cyst of Hattori, know that you are not alone. While rare, these cysts are usually benign, and treatment outcomes are excellent when surgery is needed. Most importantly, keep asking questions and working with your doctors — even if they haven’t seen this before.

If you’ve found this post after reading your scan report, I hope it helps you feel a little less in the dark.

References & Further Reading

1. Hattori, H. Müllerian cyst of the mediastinum: report of a case and review of the literature. Pathology International. 2005.
   Link to abstract

2. Sekimura, A., et al. Müllerian cyst in the posterior mediastinum: a case report and literature review. Surgical Case Reports. 2018.
   Full text

3. Chen, X., et al. Posterior mediastinal Müllerian cyst characterized by serous papillary features: a case report. Journal of Cardiothoracic Surgery. 2024.
   Full text

4. Radiopaedia. Benign paravertebral cyst of Hattori (Müllerian cyst).
   Radiopaedia case study

5. Thomas-de-Montpréville, V., et al. Müllerian cysts of the posterior mediastinum: a clinicopathological entity derived from Müllerian tissue. Modern Pathology. 2007.
   Abstract

6. Diagnostic Imaging Journal. Imaging of Cystic and Cyst-like Lesions of the Mediastinum with Pathologic Correlation.
   Overview article