A Rare Case of Hyalinizing Clear Cell Carcinoma Presenting in the Nasopharynx

Hyalinizing clear cell carcinoma (HCCC) is a rare, low grade, tumor of the salivary glands that was first described in 1994. It is unusual for this tumor to present in the nasopharynx. Currently in literature, HCCC presenting in the nasopharynx has only been documented in two case reports and once in a case as part of a series review. HCCC is one tumor in a list of clear cell-containing tumors of salivary gland that also includes odontogenic tumors, and metastasis from renal cell carcinoma. Diagnosis is generally difficult and controversial. Recently, there have been advances in the use of fluorescent in-situ hybridization (FISH) analysis in the diagnoses of salivary gland tumors.

In this case report, we describe a patient with an unusual nasopharyngeal presentation of a hyalinizing clear cell carcinoma (HCCC), a rare tumor of salivary gland origin. This is the first report of a nasopharyngeal HCCC diagnosed with the aid of FISH analysis, and it is the first documented nasopharyngeal HCCC excised with a pure endoscopic endonasal approach. A 38-year-old male with no cancer history presented to his primary care physician with nasal congestion. Despite medical management, he later developed purulent drainage, facial pressure pain, and ear plugging. A nasopharyngeal mass was identified on CT and MRI. A trans-nasal endoscopic biopsy was performed. Histological staining showed cords and trabecular bands of pleomorphic tumor cells with hyperchromatic nuclei and clear cytoplasm. Tumor cells were surrounded by fibrotic tissue. Immunohistochemical stains were strongly positive for AE1/AE3, CK5/6, and p63, and weakly positive for calponin. The histopathology and immunoprofile suggested a differential diagnosis of HCCC and MEC.

The distinction between HCCC and MEC is important. MEC tumors are graded by a combination of low cystic content, invasive tumor front, perineural invasion, anaplasia, and mitotic activity. Although HCCCs have little mitotic activity, they show low cystic content, high infiltrative margin, and, often, perineural invasion. If improperly diagnosed, a MEC grading system may erroneously label HCCC tumors as high grade even though HCCC tumors behave in an indolent manner with only local invasion and rare metastasis. Fluorescent in-situ hybridization (FISH) analysis was used to determine the final diagnosis. An EWSR1 translocation was found. These findings were consistent with EWSR1-ATF1 fusion, a molecular finding that has recently been reported as a marker of HCCC. The mass was excised using a pure endoscopic endonasal approach. A small amount of the tumor was left behind due to lack of anatomical plane between the mass and the right internal carotid artery. The patient received postoperative concurrent proton beam radiation therapy and chemotherapy as radiosensitizer.