Poorly differentiated neuroendocrine carcinoma


A poorly differentiated neuroendocrine carcinoma is a type of cancer made up of specialized cells called neuroendocrine cells. Neuroendocrine cells normally produce hormones and are found throughout the body, including the lungs, digestive tract, and many other organs. The term “poorly differentiated” means the cancer cells look very abnormal compared to healthy neuroendocrine cells. Because of this abnormal appearance, pathologists often need special tests to confirm the diagnosis. Poorly differentiated neuroendocrine carcinomas are aggressive cancers that usually grow quickly and may spread rapidly.

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

Poorly differentiated neuroendocrine carcinomas can develop anywhere neuroendocrine cells exist, but they most commonly arise in:

  • The lungs, where they are often called small cell lung cancer or large cell neuroendocrine carcinoma.

  • The digestive system, including the stomach, pancreas, intestines, and rectum.

  • The genitourinary system, such as the bladder and prostate.

Although these are common locations, these carcinomas can occasionally occur in other parts of the body.

What are the symptoms of a poorly differentiated neuroendocrine carcinoma?

Symptoms depend on where in the body the cancer is located, but commonly include:

  • In the lungs: Cough, shortness of breath, chest pain, or coughing up blood.

  • In the digestive system: Abdominal pain, bloating, nausea, vomiting, or changes in bowel habits.

  • In the bladder or prostate: Difficulty urinating, blood in the urine, or pain during urination.

General symptoms can also occur, including unexplained weight loss, fatigue, and loss of appetite.

What causes poorly differentiated neuroendocrine carcinoma?

The exact cause is often unknown, but certain factors increase the risk, including:

  • Smoking: Particularly for cancers developing in the lungs.

  • Chronic inflammation: Long-term inflammation in certain organs may lead to these cancers.

  • Genetic mutations: Specific changes in genes within neuroendocrine cells can trigger uncontrolled growth.

Many people develop this type of cancer without any identifiable cause.

What do pathologists see under the microscope?

When viewed under the microscope, poorly differentiated neuroendocrine carcinomas contain abnormal cells arranged in clusters or sheets. The cancer cells usually have large, irregular nuclei (the part of the cell containing DNA) and very little cytoplasm (the area around the nucleus). These cancer cells divide rapidly, and pathologists frequently see evidence of active cell division (mitotic figures).

Pathologists use special tests called immunohistochemistry to confirm the diagnosis. Typical results include:

  • Synaptophysin and chromogranin: Usually positive, confirming the neuroendocrine origin of the cells.

  • Ki-67: High levels indicate that the tumour cells are dividing quickly, consistent with aggressive behaviour.

  • TTF-1 (thyroid transcription factor-1): Often positive in neuroendocrine carcinomas originating in the lungs.

Types of poorly differentiated neuroendocrine carcinoma

Pathologists classify poorly differentiated neuroendocrine carcinoma into two main types based on how the cells look under the microscope:

Small cell neuroendocrine carcinoma

This type is made up of small, round cells with minimal cytoplasm and dark nuclei. It most commonly occurs in the lungs and is known as small cell lung cancer. Small cell carcinoma tends to be very aggressive, growing and spreading quickly.

Large cell neuroendocrine carcinoma

This type consists of larger cells with more cytoplasm and irregular nuclei. It can develop in the lungs, digestive tract, or other organs. Like small cell carcinoma, large cell neuroendocrine carcinoma is aggressive and rapidly growing.

Metastatic poorly differentiated neuroendocrine carcinoma

When a poorly differentiated neuroendocrine carcinoma spreads from its original site to other parts of the body, this process is called metastasis. Cancer cells spread through the bloodstream or lymphatic system, forming new tumours in distant organs.

Common locations for metastasis include:

  • Liver

  • Bones

  • Brain

  • Lungs (if the original tumour started elsewhere)

Metastatic cancer can cause additional symptoms, such as abdominal pain, jaundice, bone pain, or neurological issues. Treatment in these cases often focuses on managing symptoms and slowing disease progression.

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

Poorly differentiated neuroendocrine carcinomas are aggressive cancers and typically grow and spread quickly. The prognosis (expected outcome) depends on several factors, including tumour size, location, how far the cancer has spread, and how well it responds to treatment. Treatment typically includes chemotherapy, and in some situations, surgery or radiation therapy may be used.

If detected early, before significant spread has occurred, treatment can be more effective, leading to a better prognosis. However, once the cancer has spread widely (metastasized), the goal shifts toward controlling symptoms, maintaining quality of life, and slowing progression of the disease. Regular follow-up with your healthcare team is important for managing symptoms and adjusting treatment plans as needed.

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