• An 80-year-old female presented with an ulcerated nodule on the left cheek. An excision was performed.

The actual H&E slide will be presented as virtual microscopy.

The following images are representative of the virtual image.

• Based on the H&E findings on the skin excision, what is your differential diagnosis? List your 5 top choices. Once you have finished this section, you may not return to it

• Atypical fibroxanthoma

• Basal cell carcinoma

• Large cell lymphoma

• Leiomyosarcoma

• Melanoma

• Metastatic carcinoma

• Metastatic sarcoma

• Pleomorphic fibroma

• Primary undifferentiated pleomorphic sarcoma

• Squamous cell carcinoma

• Atypical fibroxanthoma

• Leiomyosarcoma

• Melanoma

• Primary undifferentiated pleomorphic sarcoma

• Squamous cell carcinoma

Answers for Diff Dx

• Based on the clinical history and your differential diagnosis, which immunostains would most likely be helpful in arriving at a definitive diagnosis? Please choose 3 stains. Once you have chosen, you cannot choose an additional panel of immunostains.

• CD3

• CD45

• CD117

• Cytokeratin

• CK7

• CK20

• Desmin

• Factor XIIIa

• GATA-3

• MOC31

• PAX5

• PAX8

• S-100 protein

• Vimentin

Answers for Stains

• Cytokeratin

• Desmin

• S-100

• The following immunostains were performed

S-100 protein

Desmin

Cytokeratin

What is the best diagnosis?

• Squamous cell carcinoma