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Rare Cancers Australia
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Histiocytic Disorders (R Group)

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 cells (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 localised to the skin or mucosal surfaces, such as the mouth, nose, and gastrointestinal system. The M group, also known as malignant histiocytic disorders, are classified by the presence of malignant (or cancerous) 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 nodes. 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 R group histiocytic disorders, such as familial Rosai-Dorfman disease (RDD), sporadic RDD, classic (nodal) RDD, extranodal RDD, neoplasia-associated RDD, and immune disease-associated RDD.

R group histiocytic disorders are slightly more common in males, with the average age of diagnosis varying between subtypes. However, anyone can develop this disease.

Types of R Group Histiocytic Disorders

R group histiocytic disorders are broadly classified into two categories: familial RDD (RDD with a family history) and sporadic RDD (RDD without a family history). It can also be further categorised based on tumour location and associated conditions.

Classic (Nodal) Rosai-Dorfman Disease

Classic RDD, also known as nodal RDD, is the most common subtype of R group histiocytic disorders that causes swelling of the lymph nodes in the body. In most cases, it affects the lymph nodes of the neck but in rare cases in can develop in the groin, retroperitoneum (a space located behind the abdomen that contains many important bodily structures such as the kidneys) and/or mediastinum (space between the lungs that holds many important structures, including the heart, trachea, and oesophagus). Classic RDD most commonly affects children and young adults, is generally benign, and can have an excellent prognosis.

Extranodal Rosai-Dorfman Disease

Extranodal RDD is a less common subtype of R group histiocytic disorders that is found in areas other than the lymph nodes. Most commonly, extranodal RDD occurs in the skin and is called cutaneous RDD, however it can also develop in the nasal cavity/sinuses, bone, eyes/eyelids, and central nervous system (CNS). Unlike classic RDD, extranodal RDD tends to affect older individuals generally between 40-60 years old. In some cases, extranodal RDD can be aggressive, but it can have a good prognosis when found early.

Cutaneous Rosai-Dorfman Disease

Cutaneous RDD is the most common subtype of extranodal RDD which occurs on the skin. While it is a type of RDD, cutaneous RDD is classified as a cutaneous non-Langerhans cell histiocytosis and is classified as a C group histiocytic disorder. 

For more information on C group histiocytic disorders, please refer to the Rare Cancers Australia Histiocytic disorders (C Group) page.

Neoplasia-associated Rosai-Dorfman Disease

Neoplasia-associated RDD is a rare subtype of R group histiocytic disorders that causes RDD to develop in association with another condition in the body, such as:

The aggressiveness and prognosis of this disease often vary based on the condition it’s associated with.

Immune Disease-associated Rosai-Dorfman Disease

Immune disease associated RDD is a rare subtype of R group histiocytic disorders that causes RDD to develop in association with an autoimmune condition in the body, such as:

  • Systemic lupus erythematosus. 
  • Idiopathic juvenile arthritis.
  • Autoimmune haemolytic anaemia.
  • Human Immunodeficiency virus (HIV).

The aggressiveness and prognosis of this disease often vary based on the condition it’s associated with.

Treatment 

Each patient with an R 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 staging system for this disease.  Instead of staging and grading, your doctor will recommend a treatment plan based on the following factors:   

  • Cancer location.
  • Whether or not the tumour(s) have spread.
  • Your age.
  • General health.
  • Treatment preferences.

Your doctor may recommend genetic testing, 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 R group histiocytic disorder may include:

  • Watch and wait (may be an option for some asymptomatic patients without an associated condition).
  • Surgery to remove as much of the tumour(s) as possible.
  • Steroids (rare).
  • Chemotherapy (rare).
  • Clinical trials.
  • Palliative care.

For more information on the treatment options, please refer to the Rare Cancers Australia treatment options page. 

Risk factors 

While the cause of RDD remains unknown, the following factors may increase the likelihood of developing the disease:

Not everyone with these risk factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned. 

Early symptoms 

The symptoms of RDD often vary based on the location of the tumour(s).

General Symptoms of RDD

General symptoms of RDD may include:

  • Fever.
  • Paleness of the skin.
  • Unexplainable weight loss/loss of appetite.
  • Fatigue.
  • Night sweats.
  • General feeling of unwellness (malaise).
  • Persistent runny nose (rhinitis).
  • Enlargement of liver (hepatomegaly) and/or spleen (splenomegaly).

Symptoms of RDD in Lymph Nodes

In addition to the general symptoms listed above, patients with RDD in the lymph nodes may also experience painless, swollen lumps on both sides of the neck. In rare cases, these lumps may also appear in the groin, armpits, and/or the mediastinum. 

Symptoms of Cutaneous RDD

In addition to the general symptoms listed above, patients with RDD in the skin may also experience:

  • Yellow or purple skin lesions.
  • A reddish, rash-like inflammation of the skin.
  • Small, solid papules and/or nodules on the skin.
  • Pus-filled skin lesions.

Symptoms of RDD in the Nasal Cavity/Sinuses

In addition to the general symptoms listed above, patients with RDD in the nasal cavity and sinuses may also experience:

  • Blocked nasal passages (nasal obstruction).
  • Nosebleeds.
  • Nasal deformities.
  • Nasal mass.
  • Reduced hearing.
  • Lost sense of smell.
  • Difficulty breathing.

Symptoms of RDD in Bones

In addition to the general symptoms listed above, patients with RDD in bones may also experience:

  • Pain in affected area.
  • Swelling in affected area.
  • Decreased calcium in the bones.
  • Easily broken bones.
  • Weakness in affected area.

Symptoms of RDD in the CNS

In addition to the general symptoms listed above, patients with RDD in the CNS may also experience:

  • Headaches.
  • Seizures.
  • Facial paralysis.
  • Changes in motor function.
  • Changes in sensory function.

Symptoms of RDD in the Eyes/Eyelids

In addition to the general symptoms listed above, patients with RDD in the eyes or eyelids may also experience:

  • Changes in vision, such as double vision.
  • Bulging of the eyes.

Not everyone with the symptoms above will have cancer, but see your general practitioner (GP) if you are concerned. 

Diagnosis/diagnosing 

If your doctor suspects you have an R group histiocytic disorder, they will order a variety of tests to confirm the diagnosis and refer you to a specialist for treatment.

Physical examination

Your doctor will collect your overall medical history, as well as your current symptoms. Following this, they may examine your body to check for any abnormalities.

Neurological exam

A neurological examination assesses sensory and motor functions, and can generally be done in your GPs office. The doctor may check your vision, hearing, balance, coordination, strength, and reflexes, depending on the signs and symptoms you have described. Any problem that is detected in this exam can help determine which portion of the CNS needs further investigation.

Imaging & blood tests

The doctor will take images of your body using magnetic resonance imaging (MRI), a computed tomography scan (CT scan), positron emission tomography scan (PET scan) and/or ultrasound, depending on where it is suspected the cancer is. The doctor may also look at other parts of the body and looks for signs of metastasis. Additionally, a blood test may be taken to assess your overall health and help guide treatment decisions.

Biopsy

Once the location(s) of the cancer has been identified, the doctor will perform a biopsy to remove a section of tissue using a needle. The tissue sample will then be analysed for cancer cells.  

Imaging tests

The doctor will take images of your body using magnetic resonance imaging (MRI), a computed tomography scan (CT scan), ultrasound, bone scan and/or positron emission tomography (PET scan), depending on where it is suspected the cancer is. The doctor may also look at other parts of the body and look for signs of metastasis. 

Prognosis (Certain factors affect the prognosis and treatment options) 

While it is not possible to predict the exact course of the disease, your doctor may be able to give you a general idea based on the rate and depth of tumour growth, susceptibility to treatment, age, overall fitness, and medical history. Generally, early-stage R group histiocytic disorders have a better prognosis and survival rates. However, if the tumour has become malignant and spread, the prognosis may not be as good and there may be a higher risk of recurrence. It is very important to discuss your individual circumstances with your doctor to better understand your prognosis. 

References 

Some references are to overseas websites. There may be references to drugs and clinical trials that are not available here in Australia.