Sinus histiocytosis


Sinus histiocytosis is a term pathologists use to describe an increased number of specialized immune cells, called histiocytes, within small channels or spaces known as sinuses inside lymph nodes. Lymph nodes are small, bean-shaped organs throughout the body that help fight infections. Sinus histiocytosis is a non-cancerous change commonly seen when lymph nodes react to infection, inflammation, or other stress in the body.

What causes sinus histiocytosis?

Sinus histiocytosis usually happens when the body’s immune system is activated in response to various conditions, such as:

  • Infections: Viral or bacterial infections can cause histiocytes to accumulate in the lymph nodes.

  • Inflammation: Chronic inflammatory conditions, like autoimmune diseases, can lead to sinus histiocytosis.

  • Immune response to cancer: Sometimes, lymph nodes near a tumour can show sinus histiocytosis as the immune system attempts to fight cancer cells.

Sinus histiocytosis itself is not cancerous but can indicate an ongoing immune response in the body.

How do pathologists identify sinus histiocytosis?

Pathologists examine lymph node tissue under a microscope after staining it with special dyes (usually hematoxylin and eosin, or H&E). When they see an increased number of histiocytes in the sinuses of a lymph node, they describe the finding as sinus histiocytosis. These histiocytes typically appear as larger cells with abundant pale-pink or clear cytoplasm and round nuclei.

Is sinus histiocytosis harmful?

Sinus histiocytosis alone is not harmful. It is typically a normal reaction of the immune system. However, it can indicate an underlying condition such as infection or inflammation that may require further evaluation or treatment.

Does sinus histiocytosis indicate cancer?

No, sinus histiocytosis itself is not a type of cancer. Instead, it usually represents a benign immune reaction to infection, inflammation, or other immune stresses. However, sinus histiocytosis can sometimes be seen in lymph nodes near cancers, reflecting the body’s immune response to tumour cells.

Questions to ask your doctor

  • What does sinus histiocytosis mean for my health?

  • Does this finding indicate an infection or inflammation?

  • Should I undergo additional tests or procedures based on this finding?

  • Could sinus histiocytosis mean there’s cancer or another serious condition present?

  • What follow-up or treatment, if any, do you recommend?

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