What is the Difference Between Isolated Tumor Cells and Micrometastases

The key difference between isolated tumor cells and micrometastases is that isolated tumor cells are single tumor cells or tumor cell clusters that are not greater than 0.2 mm in size while micrometastases are a small collection of tumor cells that are not greater than 2 mm in size.

In the process of metastasis, cancer cells break away from primary cancer and travel through the blood or lymph system. Then, these cells form new tumors in other parts of the body. Metastatic cancer is the same type of cancer as the primary tumor. Metastasis is normally distinguished from cancer invasion. Isolated tumor cells and micrometastases are two types of tumor cells associated with metastasis.

CONTENTS

1. Overview and Key Difference
2. What are Isolated Tumor Cells
3. What are Micrometastases
4. Similarities –  Isolated Tumor Cells and Micrometastases
5. Isolated Tumor Cells vs Micrometastases in Tabular Form
6. Summary –  Isolated Tumor Cells vs Micrometastases

What are Isolated Tumor Cells?

Isolated tumor cells (ITCs) are single tumor cells or tumor cell clusters that are not greater than 0.2 mm in size. Isolated tumor cells have qualitative features as well. They have no malignant activity (eg, no proliferation and no stromal reaction) and are located in lymphatic sinuses. The identifier “i” is used to indicate isolated tumor cells that are usually detected by immunohistochemistry and can be verified with hematoxylin and eosin (H&E) statin. According to American Joint Committee on cancer (AJSS) staging manual definition, isolated tumor cells are not greater than 0.2 mm and are usually detected by immunohistochemistry (IHC) or molecular methods. Therefore, localization is not a defining criterion for defining isolated tumor cells in the above statement. Moreover, isolated tumor cells are denoted as pN0[i+].

Isolated tumor cells are also known as circulating tumor cells. The majority of isolated tumor cells or circulating tumor cells do not successfully metastasize. Only a few isolated tumor cells (0.05%) survive and initiate metastatic focus. When isolated tumor cells successfully land on a distant organ and establish, they are called disseminated tumor cells (DTCs).

What are Micrometastases?

Micrometastases are a small collection of tumor cells bigger than 0.2 mm but not greater than 2 mm. They usually show extravasation. This means they invade and penetrate the lymphatic vessels or lymphatic sinus wall. They can spread to another part of the body through the lymphovascular system.

Micrometastases are normally very few in quantity. Therefore, they cannot be seen with imaging tests such as mammograms, MRI, ultrasound, PET, or CT scans. They can be typically identified through hematoxylin and eosin staining. The detection of micrometastases in sentinel lymph nodes can be done by imaging. If the micrometastases are present in the sentinel lymph node, the treatment option is to remove these nodes surgically. Depending on the cancer cell progression, the surgeon will determine the level of dissection.

What are the Similarities Between Isolated Tumor Cells and Micrometastases?

• Isolated tumor cells and micrometastases are two types of tumor cells associated with metastasis.
• They are a cluster of tumor cells.
• Both types can be identified in the lymphatic system.
• These may have important prognostic and therapeutic value in cancer treatment.

What is the Difference Between Isolated Tumor Cells and Micrometastases?

Isolated tumor cells are single tumor cells or tumor cell clusters that are not greater than 0.2 mm in size while micrometastases are a small collection of tumor cells bigger than 0.2 mm but not greater than 2 mm. So, this is the key difference between isolated tumor cells and micrometastases. Furthermore, isolated tumor cells are located in lymphatic sinuses, while micrometastases are located outside of the lymphatic sinuses.

The below infographic lists the differences between isolated tumor cells and micrometastases in tabular form for side by side comparison.

Summary – Isolated Tumor Cells vs Micrometastases

In metastasis, the cancer cells break and travel away from where they are first formed. Isolated tumor cells and micrometastases are two types of tumor cells associated with metastasis. Isolated tumor cells are single tumor cells or tumor cell clusters that are not greater than 0.2 mm in size. Micrometastases are a small collection of tumor cells that are between 0.2 mm to 2 mm in size. Thus, this is the key difference between isolated tumor cells and micrometastases.

Reference:

1. Ji, Rui-Cheng. “Lymph Nodes and CANCER Metastasis: New Perspectives on the Role of Intranodal Lymphatic Sinuses.” International Journal of Molecular Sciences, MDPI, 28 Dec. 2016.
2. “Micrometastasis.”  An Overview | ScienceDirect Topics.

Image Courtesy:

1. “Circulating-tumor-dna-article. v300237192” By Jonathan Bailey / NHGRI –  (CC BY-SA 4.0) via Commons Wikimedia
2. “Lymph node with metastatic melanoma” By Gabriel Caponetti at English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia