A hygroma is a general medical term for a swelling or sac filled with fluid, often developing beneath the skin or in soft tissues. The word itself comes from the Greek term for “water-containing tumor,” although a hygroma is not cancerous. Because this term applies to different conditions with distinct origins, a deeper understanding requires separating the congenital type from the acquired type. The location and cause determine the seriousness and the necessary medical approach.
Defining Hygromas: Types and Locations
A cystic hygroma, now more accurately termed a macrocystic lymphatic malformation, is a congenital condition, meaning it is present at birth. This type is a collection of fluid-filled sacs resulting from a malformation of the lymphatic system during the first few weeks of pregnancy. Cystic hygromas are most commonly found in the head and neck region, with about 80% occurring in the cervicofacial area. The remaining 20% are typically found in the armpit, or axilla.
The second type is an acquired or adventitious hygroma, which develops later in life due to external factors. This non-epithelial-lined, fluid-filled sac forms over a bony prominence or pressure point. It occurs in areas subject to repeated pressure or friction. This type of hygroma is essentially an inflammatory response where the body attempts to cushion a repeatedly traumatized area.
Identifying the Condition: Causes and Symptoms
Cystic hygromas arise from a failure of the developing lymphatic system to connect properly with the venous system in the embryo, causing lymph fluid to collect and form large cysts. These are most often noticed prenatally via ultrasound or shortly after birth. Approximately 50% to 60% of cases diagnosed before birth are associated with chromosomal abnormalities, such as Turner syndrome or Down syndrome. The primary symptom is a soft, spongy, and painless lump, most frequently located on the posterior side of the neck. If the growth is large or rapidly expanding, it can compress surrounding structures, leading to difficulty breathing or swallowing.
Acquired hygromas develop due to chronic, repetitive friction or minor trauma over a bony area. The constant pressure causes a localized inflammatory response in the subcutaneous tissue. The body forms a dense fibrous capsule around a pocket of serous fluid as a protective mechanism. Symptoms include a localized, soft, and fluctuant swelling over a pressure point, such as the elbow. This type is usually painless unless it becomes infected or ulcerated due to continued irritation.
Medical Management: Diagnosis and Treatment
Diagnosis for any hygroma begins with a physical examination, assessing the mass’s size, location, and consistency. For cystic hygroma, prenatal diagnosis is common, as routine ultrasound scans sometimes reveal excess fluid collection in the baby’s neck. After birth, imaging techniques like ultrasound or Magnetic Resonance Imaging (MRI) are used to determine the exact size, extent, and fluid content of the cyst, which helps differentiate it from other masses.
The treatment for cystic hygroma often involves either surgical removal or sclerotherapy, depending on the size and location. Surgical excision is considered the standard approach, though complete removal can be challenging due to the lesion’s tendency to infiltrate surrounding tissues. Sclerotherapy involves injecting a chemical agent directly into the cyst to cause an inflammatory reaction that shrinks the sac. For small, asymptomatic cystic hygromas, doctors may choose a period of watchful waiting, as some lesions can resolve spontaneously.
Managing an acquired hygroma is generally a simpler process focused on eliminating the cause of friction and inflammation. Initial treatment involves conservative measures like rest, applying protective padding to the affected area, and providing a softer surface to rest on. If the acquired hygroma is large, infected, or significantly inflamed, medical intervention may be required. In complicated cases, this can include draining the fluid or, in rare instances, surgical removal.