It’s been a while since we’ve had an unknown case! These cases are a nice, low-stress way to test your pathology knowledge. Take a look at the question and photo, and then see if you can answer before scrolling down to see the answer and explanation.

A 15-year-old male presents with an ill-defined, large mass deep in his right thigh. A biopsy is performed, and a representative section is shown here.

Case 22

What is the diagnosis?

A. Burkitt lymphoma
B. Malignant fibrous histiocytoma
C. Leiomyosarcoma
D. Rhabdomyosarcoma
E. Ganglioneuroblastoma





(Scroll down for the answer)








The diagnosis in this case is rhabdomyosarcoma. Rhabdomyosarcoma is divided into three variants: embryonal, alveolar and pleomorphic rhabdomyosarcoma. The alveolar variant, as shown in this case, commonly arises in the deep musculature of the extremity, and represents 20% of all cases of rhabdomyosarcoma. Histologically, the tumor cells are aligned along fibrous septae that create spaces resembling the alveolar spaces in the lung. The tumor cells are small to moderate in size, with minimal cytoplasm. Prognosis is poor, particularly for tumors which have a t(2;13) translocation.

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
  • Case 13: 36-year-old female with painless lower leg nodule
  • Case 14: 58-year-old female with several-year history of pelvic pain
  • Case 15: 52-year-old male with abdominal pain and bloody diarrhea
  • Case 16: 42-year-old female with tinnitus, hearing loss, and a mass at the cerebellopontine angle
  • Case 17: 52-year-old male with HIV with profuse, watery diarrhea
  • Case 18: 44-year-old male with history of progressive weakness and visual changes
  • Case 19: 20-year-old male with large, deep thigh mass
  • Case 20: 60-year-old male with multiple lung nodules
  • Case 21: 3-year-old boy with 7 cm abdominal mass