A 60-year-old woman comes to the physician because of

a 4-week history of a severely itchy rash. She initially noticed

a small, itchy bump that gradually became a generalized rash. She reports that

the itching is extremely bothersome and often wakes her up at night. Yesterday,

she also noticed a lump in the left axilla. Examination shows diffuse reddening

of the skin with fine scales involving the neck, shoulders, back, abdomen,

and extremities. The nails appear normal. A peripheral blood smear shows

significant multiplication of one cell type which is shown in the picture. Which

of the following cell types is it?