This 8-year-old neutered male domestic shorthaired cat has a two-month history of pruritic generalized crusting dermatitis that has been poorly responsive to antibiotics and bathing (Figure 1). Six weeks ago, a mediastinal thymoma was surgically removed; the crusting dermatitis preceded the surgery and persisted unchanged postoperatively.

Figure 1

Cytologic examination is performed on samples of exudate under pinnal crusts (Figure 2) and on moist crusts from the ventral trunk (Figure 3).

Figure 2

Figure 3

What is your tentative diagnosis?

a) Cutaneous lymphoma

b) Pemphigus foliaceus

c) Dermatophytosis

d) Bacterial pyoderma

e) Thymoma-associated exfoliative dermatosis

f) Both B and D