The American Society of Dermatopathology

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Interactive Case Study - June 2018

70-year-old with rubbery mass on lower back

Daniel C. Morse, BS ; Mildred Lopez Pineiro, MD; Ronald P Rapini, MD

Question 1:

A 70-year-old female presented with a new, solitary lesion on the paramedian mid-back for the past five weeks. Her past medical history was significant for malignant melanoma on mid-back 16 years ago, clear cell renal cell carcinoma with a unilateral nephrectomy performed one year ago, and multiple basal cell carcinomas. The patient did not use tobacco or alcohol and was on no medications. Physical exam revealed a 3 cm x 5 cm x 3.5 cm rubbery mass with focal erythema and slight tenderness on the left paramedian back just lateral to the scar from the previous melanoma. Further skin and lymph node examination was unremarkable. Biopsy of the lesion revealed the following histopathology (Figures 1-5).

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Figure 1. 2X

Figure 2. 10x

Figure 3. 20X

Figure 4. 40X

Figure 5. CK-AE1-AE3

What is the best diagnosis?