Why has this lump suddenly become tender?

Case 1: A 12-year-old boy with a childhood history of asthma has a pruritic rash that has flared around the elbows. He is active in sports and recently transitioned from soccer to basketball. He is otherwise healthy and takes no medication. His family has a dog.

What is your clinical impression?

A. Tinea corporis.

B. Atopic dermatitis.

C. Psoriasis.

D. Contact dermatitis.

E. Asteatotic eczema.

Case 1: This patient had an exacerbation of atopic dermatitis, B, with an overlay of asteatotic eczema, E. The rash erupted when he started bathing twice a day because of his sports activities and when the weather started turning cooler. The outbreak was exacerbated by his use of antibacterial soap and a washcloth. His condition resolved after he was instructed in proper bathing and moisturizing techniques.

Atopic dermatitis occurs on flexural surfaces, such as antecubital and popliteal fossae. This condition is also associated with asteatotic changes such as nummular eczema, eczema craquelé, and xerosis, which are more commonly found on the lower legs and trunk.

Tinea corporis is not bilateral or as extensive as this patient's condition. The lesions of psoriasis are keratotic and more discrete. Contact dermatitis usually resolves within 2 to 3 weeks and the patient typically has an exposure history.

Case 2: A 56-year-old man has a slowly growing asymptomatic lesion on his forehead. It has a soft, doughy consistency and, when pressed, feels almost as if it could be pushed back through the skin.

What type of growth is this?

A. Intradermal nevus.

B. Basal cell carcinoma.

C. Neurofibroma.

D. Sebaceous hyperplasia.

E. Seborrheic keratosis.

Case 2: A biopsy confirmed the diagnosis of neurofibroma, C. This benign lesion often feels compressible through a dermal defect. No treatment is necessary.

The other entities in the differential are not compressible; nor do they feel soft and doughy.

 

Case 3: A month ago, this slightly tender nodule suddenly appeared on the arm of an otherwise healthy 63-year-old woman.

Can you identify the nodule?

A. Seborrheic keratosis.

B. Wart.

C. Basal cell carcinoma.

D. Intradermal nevus.

E. Keratoacanthoma.

Case 3: A biopsy showed the lesion to be a keratoacanthoma, E. This low-grade squamous cell carcinoma is characterized by an erythematous nodule with a central keratotic core. Treatment consists of excision with clear margins.

Seborrheic keratoses and warts have a more corrugated surface. Basal cell carcinomas and nevi are not typically keratotic.

 

Case 4: For 6 months, a 43-year-old man has had a lump on his neck. It had been asymptomatic previously but has become swollen and tender during the past few days.

What are you looking at here?

A. Staphylococcal furuncle.

B. Infected epidermoid cyst.

C. Ruptured epidermoid cyst.

D. Dermatofibroma.

E. Insect bite reaction.

Bonus question: What is the difference between a sebaceous cyst and an epidermoid cyst?

Case 4: This is an epidermoid cyst that has ruptured, C, and produced the inflammatory response seen here. Because these lesions are not infected, they are not treated with antibiotics. Although they sometimes respond to intralesional corticosteroids, they often need to be incised and drained. The contents, including the cyst wall, must be removed to prevent recurrence.

Staphylococcal furuncles and infected cysts usually appear more inflamed and are more tender than this patient's lesion. Dermatofibromas are asymptomatic, and insect bites are pruritic.

Answer to bonus question: Sebaceous cysts arise from the neck of the sebaceous gland where it inserts into the pilosebaceous unit. Epidermoid cysts arise from the portion of the pilosebaceous unit that is above the insert of the sebaceous gland. These two cysts, which are relatively common,are not easily distinguishable clinically. They can be identified by the difference in the lining of the cyst wall on histopathological evaluation.