Skin nodules are slightly elevated lesions on or in the skin. They are larger than papules - over 5 mm in diameter. The depth of the lesion is more significant than the width. Some are free within the dermis. Some are fixed to skin above or subcutaneous tissue below.

The patient will usually consult because of concern about cosmetic appearance or the possibility of malignancy.

Differential diagnosis

Such lesions are very common, but there are numerous causes. It is important to try to define the aetiology.

Common causes

• Sebaceous cyst (epidermoid cyst) - a dermoid cyst is a variation.¹
• Lipoma.
• Basal cell carcinoma (BCC).
• Warts.
• Xanthoma.
• Acrochordons:
  • Flesh-coloured pedunculated lesions - 'skin tags'.
  • Tend to occur in areas of skin folds (therefore most common in the obese).

Less common causes

• Dermatofibroma (also called histiocytoma).
• Squamous cell carcinoma.
• Malignant melanoma.
• Pyogenic granuloma:
  • A rapidly proliferating solitary lesion that bleeds easily.
  • Is often associated with trauma.
  • Is usually less than 1 cm in diameter.
  • Typical locations include the face, fingers, and thorax.
  • Clinically, melanoma must be excluded.
• Nodulocystic acne.
• Kerato-acanthoma (also called molluscum sebaceum).
• Chondrodermatitis nodularis chronica helicis.
• Rheumatoid nodules.
• Gouty tophi.
• Keloid scars.

Rarer causes

• Vasculitic lesions such as erythema nodosum, nodular vasculitis, polyarteritis nodosa.
• Neurofibromatosis - there may be a family history and café au lait spots.
• Atypical infections including leprosy, syphilis and leishmaniasis.
• Lymphoma or metastatic carcinoma.

Presentation

The diagnosis may be clear from the presentation:

• Note the age of the patient.
• Note the position of the lesion or lesions and any changes.
• To a considerable extent it is like the surgical task of examination of a lump.
• Do not forget to enquire after systemic symptoms and general state of health.

Malignancies of the skin tend to occur in elderly people who have much solar damage to the skin, but melanoma in particular can occur in rather younger people, but usually 'sun worshippers'. On the basis that common things commonly occur, the following table will help to differentiate the common lesions:

The less common lesions may also occur, but what is most important is not to be blandly reassuring about something that requires attention whilst at the same time not taking biopsies or referring every case that is seen.

Causes for concern

• A nodule in a mole is highly significant and requires excision biopsy in case of malignancy.
• An elderly patient with a lesion in a sun-exposed area may well have a squamous or basal cell carcinoma.
• A middle-aged or elderly patient who develops widespread skin nodules over a period of a few weeks probably has an underlying carcinoma, especially if unwell and losing weight.
• Night sweats and itching with skin nodules suggests lymphoma. These are B features. Examine lymph nodes, liver and spleen carefully.
• Nodulocystic acne is very difficult and probably needs a dermatologist.

Investigations

• FBC and erythrocyte sedimentation rate (ESR) are basic investigations.
• Uric acid should be measured if nodules may be gout, e.g. on ear lobes or elbows.
• The appearance of xanthomata is fairly typical. Fasting lipid profile is required.
• Urinalysis is required if inflammatory or vasculitic skin lumps are suspected:
  • There may be proteinuria if the lumps are associated with systemic and renal disorders.
• Excision biopsy is the definitive investigation:
  • Cytology from skin scrapings can be used to diagnose BCCs.
  • If malignant melanoma is suspected, try to take a normal margin too.³

Management

The management depends upon the diagnosis, working diagnosis or differential diagnosis. It may be possible just to be reassuring but, if there is any doubt, then investigations, including biopsy are required.

Document references

1. Hanson LJ et al; Epidermal Inclusion Cyst, eMedicine, May 2010
2. Skin cancer - suspected, Clinical Knowledge Summaries (2007)
3. Improving Outcomes for People with Skin Tumours including Melanoma, NICE (2006)

Internet and further reading

• Luba M et al; Common Benign Skin Tumors. Am Fam Physician 2003;67(4):729-38; An excellent primary care overview with good images and diagnostic algorithms
• Diseases database; Cutaneous nodules.
• Dermatlas.org; Dermatology Image Atlas

Acknowledgements