Rare Pulmonary Myoepithelioma Mimicking Metastatic Lung Cancer

Overview

Pulmonary myoepithelioma is a rare lung tumour that can resemble metastatic cancer on imaging. A Redcliffe Labs-supported case report highlights how detailed lung biopsy, histopathology and immunohistochemistry (IHC) helped distinguish a benign pulmonary myoepithelioma from suspected cancer spread.

• A 42-year-old woman with a previous history of adenoid cystic carcinoma was found to have multiple nodules in both lungs and along the pleura.
• Because of her previous cancer history, the lung nodules initially raised concern for metastatic lung disease.
• CT imaging showed multiple bilateral pleuro-parenchymal nodules, with the largest measuring 1.1 cm.
• A CT-guided lung biopsy was performed for further evaluation.
• Histopathology and immunohistochemistry established the diagnosis of benign pulmonary myoepithelioma.
• The case demonstrates why imaging findings alone may not be sufficient to distinguish a rare benign lung tumour from metastatic disease.

What Is Pulmonary Myoepithelioma?

Pulmonary myoepithelioma is a rare tumour of the lung made up of myoepithelial cells. It is uncommon and can be difficult to diagnose because its microscopic and imaging features may overlap with other lung tumours.

Pulmonary myoepitheliomas can be benign or malignant. In the case reported here, the tumour was identified as benign.

Because this tumour is rare, recognising its features and using appropriate laboratory investigations are important for reaching the correct diagnosis.

Can a Lung Nodule Be Benign Even in Someone With Previous Cancer?

Yes.

A lung nodule does not automatically mean lung cancer or metastatic cancer. Lung nodules can have several causes, including benign tumours, infections, inflammation and metastatic disease.

The distinction becomes particularly important when a patient has a previous history of cancer.

In this case, multiple lung nodules were detected in a woman who had previously been treated for adenoid cystic carcinoma of the buccal mucosa. This made metastatic disease an important possibility.

However, further diagnostic testing showed that the nodules were caused by a rare benign pulmonary myoepithelioma.

What Happened in This Case?

The patient had previously been diagnosed with adenoid cystic carcinoma (ACC) of the buccal mucosa and had received treatment.

During follow-up, a CT scan of the chest showed multiple nodules involving both lungs and the pleura. The largest nodule was approximately 1.1 cm.

Because of the patient's previous cancer history and the appearance of the nodules, metastatic disease was considered.

However, the CT scan could not establish the exact nature of the nodules.

A tissue sample was therefore obtained through a CT-guided biopsy and sent for detailed pathological evaluation.

How Was the Lung Tumour Diagnosed?

The diagnosis involved three complementary steps:

1. Lung Imaging

CT imaging identified multiple bilateral pleuro-parenchymal nodules.

Imaging helped doctors identify the location, number and size of the lesions, but it could not definitively determine whether they represented metastatic cancer or another type of lung lesion.

2. Histopathology

Histopathology is the examination of tissue under a microscope.

After the lung biopsy, the tissue was examined by pathologists to assess the appearance and arrangement of the cells.

The microscopic findings suggested a myoepithelial tumour rather than typical metastatic adenoid cystic carcinoma.

3. Immunohistochemistry

Immunohistochemistry (IHC) is a laboratory technique that uses specific markers to identify proteins within cells.

IHC is particularly useful when different tumours can look similar under the microscope.

In this case, the tumour showed positivity for:

• PanCK
• SMA
• SOX10
• p63
• H-Caldesmon

It was negative for markers including:

• S100
• TTF-1
• Desmin
• Melanoma markers

The Ki-67 proliferation index was less than 2%.

Together, the histopathology and immunohistochemistry findings supported the diagnosis of benign pulmonary myoepithelioma.

Why Can Pulmonary Myoepithelioma Be Difficult to Diagnose?

The rarity of pulmonary myoepithelioma is one of the reasons diagnosis can be challenging.

A patient may present with a lung nodule or multiple lung nodules, but imaging cannot always determine the exact type of tumour.

Pulmonary myoepithelioma can also resemble other tumours microscopically. This means that histopathological examination combined with immunohistochemistry may be necessary to establish the diagnosis.

In patients with a previous cancer history, this distinction becomes even more important because a benign lesion can otherwise be mistaken for metastatic disease.

How Is a Benign Lung Tumour Distinguished From Metastatic Cancer?

The diagnosis depends on the complete clinical and pathological picture.

Doctors and pathologists may consider:

• The patient's previous medical and cancer history
• CT and other imaging findings
• The location and appearance of the lung nodules
• Histopathological features
• Immunohistochemical marker patterns
• Tumour cell proliferation

In this case, these findings collectively supported benign pulmonary myoepithelioma rather than metastatic adenoid cystic carcinoma.

Why Is Histopathology Important for Lung Nodules?

Imaging can identify an abnormality, but histopathology can help identify what that abnormality actually is.

A biopsy allows pathologists to study the cells and tissue architecture directly.

For rare lung tumours such as pulmonary myoepithelioma, this can be particularly important because the condition may not have a characteristic appearance on imaging alone.

What Role Does Immunohistochemistry Play in Lung Tumour Diagnosis?

Immunohistochemistry provides additional molecular and cellular clues that can help pathologists distinguish between different tumour types.

In pulmonary myoepithelioma, the pattern of positive and negative markers can support myoepithelial differentiation and help exclude other possible diagnoses.

This makes IHC an important part of the diagnostic work-up for rare lung tumours and diagnostically challenging biopsy specimens.

What Was the Final Diagnosis?

The final diagnosis was:

Benign pulmonary myoepithelioma with bilateral pleural involvement.

This was significant because the lung nodules had initially raised concern for metastatic cancer in a patient with a previous history of malignancy.

The diagnosis showed that the lesions represented a rare benign lung tumour rather than metastatic disease.

Did the Patient Need Additional Treatment?

Following the diagnosis of benign pulmonary myoepithelioma, no additional treatment was given for the lung tumour.

The patient was kept under clinical and radiological follow-up.

The management decision was based on the pathological diagnosis and the absence of features suggesting an aggressive tumour.

Why Is This Case Important?

This case highlights an important diagnostic challenge in lung nodule evaluation.

When multiple lung nodules are detected in a person with a previous cancer history, metastatic disease may be an important consideration. However, other conditions can produce similar findings.

The case demonstrates how combining:

Clinical history + CT imaging + lung biopsy + histopathology + immunohistochemistry

can help establish the correct diagnosis.

For rare tumours such as pulmonary myoepithelioma, accurate diagnosis can help prevent a benign lesion from being mistaken for metastatic cancer and can support appropriate clinical management.

Key Findings at a Glance

Finding	Details
Rare tumour	Pulmonary myoepithelioma
Tumour type	Benign
Patient	42-year-old woman
Previous cancer	Adenoid cystic carcinoma of the buccal mucosa
Imaging finding	Multiple nodules in both lungs and along the pleura
Largest nodule	1.1 cm
Initial concern	Metastatic cancer
Diagnostic procedure	CT-guided lung biopsy
Laboratory diagnosis	Histopathology and immunohistochemistry
Ki-67	Less than 2%
Final diagnosis	Benign pulmonary myoepithelioma
Follow-up	Clinical and radiological monitoring

Frequently Asked Questions About Pulmonary Myoepithelioma

What is pulmonary myoepithelioma?

Pulmonary myoepithelioma is a rare tumour of the lung arising from myoepithelial cells. It can be benign or malignant. Benign pulmonary myoepithelioma is uncommon and can be difficult to distinguish from other lung tumours.

Is pulmonary myoepithelioma cancer?

Pulmonary myoepithelioma can be either benign or malignant. The tumour described in this case was benign, meaning it did not show features of an aggressive malignant tumour.

Can pulmonary myoepithelioma look like metastatic cancer?

Yes. A rare pulmonary myoepithelioma can present as lung nodules and may resemble metastatic disease, particularly in a patient with a previous history of cancer. Histopathology and immunohistochemistry can help establish the diagnosis.

Can a lung nodule be benign?

Yes. Not every lung nodule is cancerous. Lung nodules can have several causes, including benign tumours, infections, inflammatory conditions and metastatic disease. The appropriate evaluation depends on the patient's clinical history and the characteristics of the nodule.

How is pulmonary myoepithelioma diagnosed?

Diagnosis may involve CT imaging, biopsy, histopathological examination and immunohistochemistry. These investigations help identify the nature of the tumour and distinguish it from other lung lesions.

Why is immunohistochemistry used for lung tumours?

Immunohistochemistry uses specific markers to identify proteins expressed by tumour cells. This can help pathologists differentiate between tumour types that may look similar under a microscope.

What is the role of a lung biopsy?

A lung biopsy provides a tissue sample that can be examined by a pathologist. It can help determine whether a lung nodule is benign, malignant, metastatic or related to another condition.

The Takeaway

A new lung nodule, particularly in someone with a previous history of cancer, can raise concern about metastatic disease. However, imaging findings alone may not always reveal the true nature of a lesion.

This case of pulmonary myoepithelioma shows how lung biopsy, histopathology and immunohistochemistry can help distinguish a rare benign lung tumour from suspected metastatic cancer.

It also highlights the importance of integrating radiology and pathology when evaluating unusual lung lesions.

Research Team

Mayanka Seth
Department of Pathology, Medicentre – Unit of Redcliffe Labs, Udaipur

Manish Seth
Department of Radiology, Medicentre – Unit of Redcliffe Labs, Udaipur

The research was conducted in collaboration with clinicians and researchers from Pacific Medical College and Hospital, Pacific Institute of Medical Sciences and other institutions.

Publication Details

Research Paper: Myoepithelioma of the Lung: A Rare Case With Bilateral Pleural Spread and Diagnostic Challenges in a Middle-Aged Female

Journal: Cureus

Publication: January 2026

DOI: 10.7759/cureus.100935

Research Area: Pulmonary Pathology | Rare Lung Tumours | Histopathology | Immunohistochemistry

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