Histiocytic disorders are a group of rare disorders characterised by the abnormal accumulation of histiocytes, a type of immune cell often found in tissues that regulates immune functions. There are three primary types of histiocytes, including monocytes (plays a role in inflammatory and anti-inflammatory responses during an immune response), macrophages (responsible for ingesting and eliminating foreign substances during an immune reaction), and dendritic cellsthe basic structural and functional unit of all living things (initiate and regulate the adaptive immune response).
Histiocytic disorders are broadly classified into five different groups: L group, C group, M group, R group, and H group. The L group, or Langerhans group, are classified as diseases involving Langerhans cells (an immune cell responsible for initiating an immune response when coming into contact with a foreign material), such as Langerhans cell histiocytosis (LCH). The C group, also known as cutaneous and mucocutaneous non-Langerhans cell histiocytosis, are classified as non-Langerhans cell histiocytic disorders that are localisedaffecting only one area of body to the skin or mucosal surfaces, such as the mouth, nose, and gastrointestinal system. The M group, also known as malignantcancerous, may grow and spread to other areas of the body histiocytic disorders, are classified by the presence of malignant cells within the tumour(s). The R group, also known as Rosai-Dorfman disease and miscellaneous non-cutaneous non-Langerhans cell histiocytosis or sinus histiocytosis, are classified as non-Langerhans histiocytic disorders that often involve lymph nodessmall bean-shaped structures that filters harmful substances from lymph fluid. The H group, also known as hemophagocytic lymphocytosis and macrophage activation syndrome, is composed entirely of hemophagocytic lymphohistiocytosis, a rare and aggressive disease caused by the overactivation of the immune system.
This page will focus specifically on M group histiocytic disorders, which includes histiocytic sarcomacancer arising from bones and/or soft tissue, Langerhans cell sarcoma, interdigitating cell sarcomas, indeterminate cell sarcoma, and malignant histiocytosis not otherwise specified.
M group histiocytic disorders are slightly more common in males, with the average age of diagnosisthe process of identifying a disease based on signs and symptoms, patient history and medical test results varying between subtypes. However, anyone can develop this disease.
Types of M Group Histiocytic Disorders
There are many types of malignant histiocytic disorders, which are classified by the types of cells they develop from.
Histiocytic Sarcoma
Histiocytic sarcoma is a very rare non-Langerhans histiocytic disorder that most commonly presents in the lymph nodes, skin, and/or gastrointestinal tract of the body. This subtype can occur randomly, however it has also been reported in patients with haematological (relating to the bloodthe red bodily fluid that transports oxygen and other nutrients around the body) cancers, most notably follicular lymphoma, myelodysplasia, and acute lymphoblastic leukaemia. Histiocytic sarcomas are often very aggressive, and may not have as good of a prognosisto predict how a disease/condition may progress and what the outcome might be as other histiocytic disorders.
Interdigitating Dendritic Cell Sarcoma (IDCS)
Interdigitating dendritic cell sarcoma (IDCS), also known as reticulum cell sarcoma, is a very rare histiocytic disorder that most commonly presents in the lymph nodes, but may also present in the bladdera hollow, muscular sac in the pelvis that stores urine, bowelportion of the digestive system that digests food (small bowel) and absorbs salts and water (large bowel); also called intestines, intestinesportion of the digestive system that digests food (small intestine) and absorbs salts and water (large intestine), also called bowel, nasopharynx, salivary glands, skin, spleen, testicles and/or tonsils. This subtype can occur randomly, however it has also been reported in patients with haematological (relating to the blood) cancers, most notably follicular lymphoma, hairy cell leukaemia, chronic lymphoblastic leukaemia, acute lymphoblastic leukaemia, and chronic myelomonocytic leukaemia. IDCS is often very aggressive, and may not have as good of a prognosis as other histiocytic disorders.
Langerhans Cell Sarcoma
Langerhans cell sarcoma (LCS) is a very rare histiocytic disorder characterised by the overproduction of Langerhans cells within a malignant tumoura tissue mass that forms from groups of unhealthy cells. In some cases, LCS is thought to develop from untreated Langerhans cell histiocytosis (LCH), however it is possible for the disease to develop sporadically. LCS is most commonly found in the skin, lungs, liver, and bone, however, may develop in other areas as well. LCS is often very aggressive, and may not have as good of a prognosis as other histiocytic disorders.
Indeterminate Cell Histiocytosis (Malignant)
Indeterminate cell histiocytosis is a rare subtype of histiocytic disorders that occurs when the disease presents with features of LCH and non-LCH. It is most commonly found on the skin, but can also occur in the lymph nodes and spleen. While ICH is generally considered benignnot cancerous, can grow but will not spread to other body parts, in rare cases it may be malignant. Malignant ICH is often more aggressive than benign ICH, and may not have as good of a prognosis.
Treatment
Each patient with an M group histiocytic disorder will present with a unique disease behaviour, with varying locations, and symptoms. As such, there is no one treatment method that will work for everyone, and there is no standard stagingthe process of determining how big the cancer is, where it started and if it has spread to other areas system for this disease. Instead of staging and grading, your doctor will recommend a treatment plan based on the following factors:
- Cancera disease where abnormal cells split without control and spread to other nearby body tissue and/or organs location.
- Whether or not the tumour(s) have spread.
- Your age.
- General health.
- Treatment preferences.
Your doctor may recommend genetic testinga procedure that analyses DNA to identify changes in genes, chromosomes and proteins, which can be used to analyse tumour DNA to help determine which treatment has the greatest chance of success, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. Your doctor will discuss the most appropriate course of treatment for you.
Treatment options for an M group histiocytic disorder may include:
- Surgerytreatment involving removal of cancerous tissue and/or tumours and a margin of healthy tissue around it to reduce recurrence to remove as much of the tumour(s) as possible.
- Radiation therapya treatment that uses controlled doses of radiation to damage or kill cancer cells.
- Chemotherapya cancer treatment that uses drugs to kill or slow the growth of cancer cells, while minimising damage to healthy cells.
- Clinical trialsresearch studies performed to test new treatments, tests or procedures and evaluate their effectiveness on various diseases.
- Palliative carea variety of practices and exercises used to provide pain relief and improve quality of life without curing the disease.
Risk factors
Because of how rare M group histiocytic disorders are, there has been limited research done into the riskthe possibility that something bad will happen factors of this disease.
Symptoms
The symptoms of an M group histiocytic disorder often vary depending on the location of the tumour (s).
Many patients with the disease may appear asymptomatic during the early stages. As the cancer(s) progress, some of the following symptoms may appear:
- A palpable massa growth of cells that come together to make a lump, may or may not be cancer on the affected area.
- Symptoms of compression of surrounding organs, such as a bowel obstructiona complete or partial blockage of the bowel/intestines.
- Persistent fevers.
- Unexplained weight loss/loss of appetite.
- Unusual rash on the skin.
- Unusual growths on the skin.
- Fatiguea state of extreme tiredness or exhaustion, can be physical or mental.
- Cytopenialow levels of red blood cells, white blood cells or platelets in the blood; one or more blood cell type can be affected.
Not everyone with the symptoms above will have cancer, but see your general practitioner (GP) if you are concerned.
Diagnosis
If your doctor suspects you have a M group histiocytic disorder, they may order the following tests to confirm the diagnosis and refer you to a specialist for treatment:
- Physical examinationan examination of your current symptoms, affected area(s) and overall medical history.
- Imagingtests that create detailed images of areas inside the body tests, potentially including:
- CT (computed tomography) scana type of medical imaging that uses x-rays and computer technology to create detailed images of the body.
- PET (positron emission tomography) scana type of medical imaging that uses radioactive tracers to create detailed images of the body.
- Blood teststesting done to measure the levels of certain substances in the blood.
- Bone marrow aspirationa procedure that involves inserting a needle into the hipbone (or the breastbone in some cases) to remove samples of solid and liquid bone marrow..
- Biopsyremoval of a section of tissue to analyse for cancer cells.
