May 2020 - Presented by Dr. Raymond Gong (Mentored by Dr. Regina Gandour-Edwards)

Clinical History:

The patient is a 50-year-old male who presented with facial swelling near the region of the right parotid gland for several months.  The patient was asymptomatic except for a rapid increase in size of the swelling.  Physical examination was notable only for an enlarged right parotid tail containing an indurated mass immediately adjacent to the retromandibular region.  A computed tomography (CT) scan demonstrated two adjacent masses with mildly ill-defined margins about the inferior aspect of the right parotid gland measuring 3.2 cm and 1.6 cm in greatest diameters.

A referral to Otolaryngology was made to discuss treatment options.  The patient elected for excision of the tumor and underwent a right superficial parotidectomy.  Intraoperatively, moderate adherence of tumor to surrounding tissue was noted.  A frozen section procedure was performed on the resected parotid mass and revealed the presence of a high-grade malignancy with lymph node involvement.

Gross Description:

The resection specimen consisted of a 5.5 x 3.9 x 2.5 cm lobular mass with patchy adherent tan-yellow fibroadipose tissue over the external surface.  Cut surfaces showed an encapsulated tan-gray tumor without hemorrhage or necrosis located 0.1 cm from the closest surgical margin. 

Microscopic Description:

Sections of the mass demonstrated nests and cords of large pleomorphic cells with vesicular nuclei, prominent nucleoli, moderate amounts of eosinophilic cytoplasm, and indistinct cell borders.  A prominent lymphoid infiltrate, composed of small mature-appearing lymphocytes with follicle and germinal center formation, was present in and around the aggregates of large pleomorphic cells (Figures 1 and 2).  Mitotic figures were readily identifiable (Figure 3).  Immunohistochemical staining for AE1/AE3 was positive in the large pleomorphic cells (Figure 4).  Synaptophysin and p40 were negative while CD45 was positive only in the lymphoid infiltrate (Figure 5).  Epstein-Barr virus-encoded RNA by in situ hybridization (EBER ISH) was negative.

Figure 1:  Low magnification view of the tumor’s solid growth pattern with a prominent admixed lymphoid infiltrate (5x)

Figure 2:  The associated lymphoid infiltrate was dense, composed primarily of small mature-appearing lymphocytes, and formed follicles with germinal centers (40x)

Figure 3:  High magnification view of the large pleomorphic tumor cells, including a mitotic figure at the center of the field (400x)

Figure 4:  Cytokeratin cocktail AE1/AE3 was positive in the large pleomorphic cells (5x)

Figure 5:  Hematopoietic lineage marker CD45 was positive in the lymphoid infiltrate and negative in the large pleomorphic cells (5x)