Nodules are small abnormal lumps of tissue that feel or look different from the surrounding area in the body.

What are nodules?

In medicine, a nodule is a small, well-defined lump or growth that can form in many places: skin, lungs, thyroid, vocal cords, joints, and internal organs. Some nodules are discovered by touch (like a lump under the skin), while others are found on scans such as X‑rays or CT scans, often described as a “spot” or “shadow.” Nodules can be benign (non‑cancerous) or malignant (cancerous), so doctors pay close attention to their size, shape, and how they change over time.

People often first hear the word “nodule” in a scan report or a doctor’s note and worry it automatically means cancer, but most nodules turn out to be harmless.

Common medical meanings

Different specialties use the word “nodule” in slightly different ways.

  • On the skin: A nodule is a firm lump, usually larger than about 1 cm, sitting in or under the skin, distinct from softer bumps (papules) or fluid‑filled cysts.
  • In the lungs: A lung (pulmonary) nodule is a round “spot” in lung tissue seen on imaging, typically less than about 3 cm in diameter; larger ones are usually called masses.
  • In the thyroid: A thyroid nodule is a lump in the thyroid gland caused by abnormal growth of thyroid tissue.
  • In joints and soft tissue: Nodules can form near arthritic joints, tendons, or in conditions like rheumatoid arthritis, where firm lumps develop under the skin.

A general dictionary definition also describes a nodule as a small rounded or irregular mass, often an abnormal “knobby” bump in the body.

What causes nodules?

Nodules have many possible causes, and the cause depends on where they appear.

  • Infections: Past bacterial or fungal infections can leave small scars or granulomas—tiny clusters of cells that show up as nodules, especially in the lungs.
  • Inflammation and injury: Chronic inflammation (for example in rheumatoid arthritis) or repeated irritation (like overused vocal cords) can trigger nodules.
  • Overgrowth of normal tissue: Some thyroid and skin nodules come from localized overgrowth of otherwise normal cells.
  • Tumors: Some nodules represent benign tumors, while others may be early cancers, which is why doctors sometimes recommend biopsy or close follow‑up.

An example many people encounter is a lung nodule found during a low‑dose CT scan: this often turns out to be scar tissue or a healed infection rather than cancer.

Are nodules serious?

Many nodules are common, painless, and never cause a problem, but some need careful evaluation.

Doctors look at features such as:

  • Size (very small nodules often carry lower risk, though size alone is not everything).
  • Shape and borders (smooth versus spiky or irregular edges).
  • Density on scans and how they change over time.
  • Symptoms (pain, rapid growth, trouble breathing or swallowing, voice changes, etc.).

Because nodules can be harmless or serious, it is important not to self‑diagnose based on the word alone. If someone notices a new lump or receives a report mentioning a nodule, the next step is to discuss it with a healthcare professional, who may recommend monitoring, further imaging, or a biopsy depending on the situation.

TL;DR: “What are nodules?”
They are small abnormal lumps of tissue that can appear in many parts of the body; most are benign, some can be cancerous, and they should be evaluated by a doctor based on their location, appearance, and any symptoms.

Information gathered from public forums or data available on the internet and portrayed here.