Case 44

1. Presented by Alisha Ware, MD and reviewed by Sean Zhang, MD, PhD.

Clinical Vignette
An elderly patient with an history of extensive craniofacial squamous cell carcinoma status post resection, radiotherapy, hardware placement, and multiple flaps/revisions presented with complaints of an enlarging scalp "scab" and resulting in hardware exposure. Physical exam revealed a large ulcerated scalp wound with an overlying gray exudate. Of note, a 1,3- β-D-glucan test was positive 3 months prior, and Histoplasma antigen testing on blood and urine and fungal blood cultures were negative at that time. The patient underwent extensive wound debridement with replacement of hardware and repeat skin flap. Tissue from the epidural space was sent for bacterial, fungal, and mycobacterial cultures, and additional epidural tissue was sent for histologic examination. Histologic sections showed extensive necrosis and the organisms seen below (Figures 1, 2). Tissue cultures were also positive, with the slant and microscopic images below (Figures 3, 4, 5).

The morphology shown in the histology, culture and microscopic images above is consistent with which of the following?