Poorly differentiated neuroendocrine carcinoma

A poorly differentiated neuroendocrine carcinoma is a type of cancer that develops from neuroendocrine cells. These are specialized cells found throughout the body that release hormones to regulate body functions. “Poorly differentiated” means the cancer cells are so abnormal that it is difficult to tell they are neuroendocrine cells without special tests.

Where are poorly differentiated neuroendocrine carcinomas typically found in the body?

Poorly differentiated neuroendocrine carcinomas can develop in many different parts of the body. They are most commonly found in:

• The lungs, where it is often called small cell lung cancer.
• The digestive system, including the pancreas, stomach, intestines, and rectum.
• The genitourinary system, such as the bladder or prostate.

These cancers may also occur in other areas, though this is less common.

What are the symptoms of a poorly differentiated neuroendocrine carcinoma?

The symptoms depend on where the tumour is located.

Possible symptoms include:

• Cough, shortness of breath, or chest pain if the tumour is in the lungs.
• Abdominal pain, bloating, or changes in bowel habits if the tumour is in the digestive tract.
• Blood in the urine or difficulty urinating if the tumour involves the bladder or prostate.

Some patients also experience general symptoms like fatigue, unintentional weight loss, or loss of appetite.

What causes poorly differentiated neuroendocrine carcinoma?

The cause of poorly differentiated neuroendocrine carcinoma is not always clear, but several factors may contribute:

• Smoking: This is a leading cause of small cell lung cancer.
• Chronic inflammation: Long-term irritation of specific organs can increase the risk of developing these cancers.
• Genetic mutations: Changes in specific genes in neuroendocrine cells may lead to cancer formation.

In many cases, the tumour appears without any apparent cause.

What are the microscope features of a poorly differentiated neuroendocrine carcinoma?

Under the microscope, poorly differentiated neuroendocrine carcinomas consist of abnormal cells arranged in sheets or clusters. These cells have large, irregularly shaped nuclei and minimal cytoplasm. They multiply quickly, and mitotic figures (dividing cells) are frequently seen.

Pathologists use immunohistochemistry to identify proteins specific to neuroendocrine tumours. Typical results include:

• Synaptophysin and chromogranin: These markers confirm the presence of neuroendocrine cells and are usually positive.
• Ki-67: This marker measures how fast the tumour cells are dividing. Poorly differentiated neuroendocrine carcinomas typically show a high Ki-67 labelling index, indicating aggressive growth.
• TTF-1 (thyroid transcription factor-1): This marker is often positive in tumours that originate in the lungs.

What are the types of poorly differentiated neuroendocrine carcinoma?

Pathologists classify poorly differentiated neuroendocrine carcinoma into two main types based on how the cells appear under the microscope: small cell type and large cell type. While these two types may look different, both are aggressive cancers that grow and spread quickly.

Small cell type

Small cell type poorly differentiated neuroendocrine carcinoma comprises small, round cells with minimal cytoplasm. The nuclei are large, with densely packed hyperchromatic (dark blue) material under the microscope. Small cell neuroendocrine carcinoma is most often found in the lungs, where it is known as small cell lung cancer. This type tends to grow and spread quickly.

Large cell type

Large cell type neuroendocrine carcinoma contains bigger cells with more cytoplasm compared to the small cell type. The nuclei are irregular but less dense. This type of cancer can occur in the lungs or other organs, including the digestive system. Like small cell type, large cell neuroendocrine carcinoma also grows quickly.

What does metastatic poorly differentiated neuroendocrine carcinoma mean?

Metastatic poorly differentiated neuroendocrine carcinoma means that the cancer has spread from its original location to other parts of the body. Metastasis occurs when cancer cells travel through the bloodstream or lymphatic system, forming new tumours in distant organs.

Common sites for metastasis include:

• The liver.
• The bones.
• The lungs (if the original tumour started elsewhere).
• The brain.

Once the cancer has metastasised, it can become more challenging to treat. Symptoms of metastatic cancer vary depending on the organs involved. For example, liver metastases may cause abdominal pain or jaundice, and bone metastases may cause severe pain or fractures. Treatment options often focus on controlling symptoms and slowing the spread of the disease.

What is the prognosis for a person with poorly differentiated neuroendocrine carcinoma?

The prognosis for a person with poorly differentiated neuroendocrine carcinoma depends on several factors, including the size and location of the tumour, whether it has spread to other parts of the body, and how well the cancer responds to treatment.

Because poorly differentiated neuroendocrine carcinomas are aggressive, they often spread quickly, making them difficult to treat. Chemotherapy is usually the first treatment option, and radiation therapy or surgery may be used in some cases. If the cancer is caught early, before it spreads, the prognosis may improve. However, if the cancer has already metastasised, the treatment focuses more on managing symptoms and maintaining quality of life. Regular follow-ups with the healthcare team are essential to monitor the disease and adjust the treatment plan as needed.

About this article

Doctors wrote this article to help you read and understand your pathology report. Contact us if you have questions about this article or your pathology report. For a complete introduction to your pathology report, read this article.

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