A 26-year-old woman with no significant medical history presented with symptoms of chronic tonsillitis. A decision was made to perform a tonsillectomy. Intraoperatively, the surgeon identified a 4 × 3-cm soft tissue mass in the left retrotonsillar fossa. A resection was performed, and multiple fragments of yellow-tan soft tissue and blood clot, measuring 7.9 × 7.5 × 2.6 cm in aggregate, along with a grossly unremarkable ipsilateral tonsil, measuring 2.5 × 1.9 × 1.2 cm, were received. Microscopically, the lesion consisted of a partially encapsulated proliferation of multivacuolated lipoblasts with prominent nuclear atypia (Figure 1 and Figure 2). Foci of epithelioid cells with eosinophillic cytoplasm and prominent nucleoli were interspersed between the lipoblasts (Figure 3). Focal tumor necrosis was present. On average, 9 mitotic figures per 10 high-power fields were identified. An immunohistochemical stain was positive for S100 protein (Figure 4). Additional stains were negative for HMB-45, Melan-A, pancytokeratin, epithelial membrane antigen, and HBME-1.
Chute DJ, Shutter J, Mills SE. Pathology Quiz Case 2. Arch Otolaryngol Head Neck Surg. 2007;133(3):303. doi:10.1001/archotol.133.3.303