Fig. 4

a-c: The area resembles desmoplastic infiltrative carcinoma. Atypical epithelioid tumor cells arranged in nested or pseudo-glandular structures (a) infiltrate the hyperplastic collagen fibers (b), which are positive for CD23 (c). d-f: The area resembles anaplastic large cell lymphoma. Atypical large tumor cells with a nested or patchy pattern fill the lymphatic sinuses (d). On high power, the tumor cells are round or polygonal with marked atypia (e) and are positive for CD21 (f). g-i: The area mimics hemangiopericytoma. Short spindle-shaped tumor cells are arranged radially around many fissure-like or dendritic thin-walled blood vessels (g) with only a few infiltrating lymphocytes (h), which are positive for CD23 (i)