Here’s an interesting case involving a painless skin nodule. Take a look at the photos and the question, then scroll down for the answer.

Unknown 13a

A 36-year-old female presents with this painless nodule on her lower leg. She notes that its size fluctuates, but that it is usually around 1 cm in diameter. When squeezed, the nodule dimples inward.

 

Unknown 13b

A biopsy is performed, and a representative section is shown here.

What is this lesion?

A. Dermatofibroma
B. Nodular basal cell carcinoma
C. Melanoma
D. Spitz nevus
E. Hemangioma

 

 

 

(Scroll down for the answer)

 

 

 

 

 

 

 

The diagnosis in this case is dermatofibroma. Dermatofibromas are benign tumors usually seen on the legs of young to middle-aged women. They usually present as tan, firm papules. Curiously, they tend to dimple inward if you squeeze them at the margins.

Under the microscope, the tumor is composed of bland, spindle-shaped cells which occasionally extend into the subcutaneous fat. You can see them making streaming patterns and sort of growing every which way in the image above.

Nobody really knows what causes these tumors. The good news is that their behavior is indolent – so usually surgical excision is curative.

If you liked this case, and want to test yourself with other unknown cases, here are some to try:

  • Case 1: 20-year-old male who died suddenly
  • Case 2: 72-year-old male with right calf mass
  • Case 3: 67-year-old female with pancytopenia
  • Case 4: 59-year-old male with severe headaches
  • Case 5: 38-year-old female with deep venous thrombi
  • Case 6: 13-year-old male with cerebellar mass
  • Case 7: 45-year-old male with pulmonary emphysema
  • Case 8: 38-year-old male with AIDS and headaches
  • Case 9: 25-year-old male with arm mass
  • Case 10: 57-year-old male with fatigue and left upper quadrant heaviness
  • Case 11: 62-year-old male with hepatosplenomegaly, skin lesions and cardiomyopathy
  • Case 12: 16-month-old infant with failure to thrive