Middle Ear Carcinoid Tumor Metastatic to an Ipsilateral Parotid Lymph Node Dr. Ben Pilch

Diagnosis: Middle ear carcinoid tumor metastatic to an ipsilateral parotid lymph node. Slide 1 Click to view with ImageScope Click to view with a Web-Based Viewer The submitted slide is a section of parotid gland that contains a tumor almost filling a parotid lymph node. The tumor is composed of low columnar epithelioid cells in a trabecular architectural arrangement. The nuclei of these cells contain somewhat prominent nucleoli in a "salt and pepper" stippled chromatin. Nuclear pleomorphism is only slight, and neither necrosis nor mitotic activity is present to a significant degree. In areas, the columnar cells surround a core of rounded smaller cells, some with eccentric nuclei, and with somewhat darker but still stippled chromatin and smaller nucleoli than those of the larger columnar tumor cells. The tumor has an organoid appearance, and the possibility of a neuroendocrine neoplasm metastatic to a parotid lymph node presents itself. Immunohistochemical studies show the tumor cells to be positive for keratin and chromogranin, confirming the diagnosis of a metastatic low-grade neuroendocrine carcinoma. The pathologic material from the patient's left middle ear tumor, removed 40 years previously, was reviewed. The specimen was a bit squeezed, but rounded epithelioid cells in a trabecular arrangement and with eccentric nuclei were present, similar to the parotid lesion. Immunohistochemical stains were positive for keratin, chromogranin, and serotonin. The histology and immunophenotype were consistent with a carcinoid tumor of the middle ear, termed by some middle ear "adenoma" or "neuroendocrine adenoma" [1]. The patient had experienced a recurrence of the ear tumor 38 years after the original excision and two years prior to the surgery for the parotid tumor. This tumor also was composed of rounded to cuboidal cells with eccentric nuclei, focally arranged in a trabecular pattern. The tumor cells were again immunohistochemically positive for keratin, chromogranin, and serotonin. These rare middle ear neoplasms are interesting lesions that have engendered a bit of discussion and some controversy regarding their nature and nomenclature. Lesions similar in histologic appearance and in clinical behavior have been called both carcinoids and adenomas. Indeed, the advent of immunohistochemistry has facilitated the appreciation that not only do middle ear tumors labeled carcinoids exhibit neuroendocrine differentiation, but almost all tumors designated middle ear adenomas do as well. These uncommon middle ear tumors are lesions of adults, with a mean age of about 40 years. The most common symptom is hearing loss, but pain, tinnitus, and other symptoms occur as well. The tumors are localized middle ear masses that occasionally extend to involve the mastoid air cells and/or external auditory canal. They often wrap around the ossicles but tend not to invade bone. Histologically, these tumors exhibit trabecular, glandular, or mixed focally glandular and focally trabecular architecture and tend to have an "organoid" pattern. They rarely have a solid architectural pattern. The tumors are composed of epithelial cells with bland cytology and a stippled "salt and pepper" chromatin. Cytology is bland, and neither necrosis nor an elevated mitotic count is encountered. Neuroendocrine differentiation is extremely common. In fact, in a large series of 48 cases, Torske and Thompson [1] found that in 46 of 48 cases, at least one neuroendocrine marker was "present to a significant degree'", and the other two cases were focally positive for human pancreatic polypeptide (HPP). Dense core neurosecretory type granules are characteristically seen ultrastructurally. Among neuroendocrine markers, chromogranin is positive in most cases, and synaptophysin and serotonin are occasionally positive. Torske and Thompson found HPP to be positive in 93.8% of their cases [1]. The neuroendocrine nature, or differentiation, of the tumor, whether called carcinoid or adenoma, is so prevalent, that Torske and Thompson have suggested the term "neuroendocrine adenoma" [1]. But why neuroendocrine adenoma and not carcinoid? Neuroendocrine neoplasms of the bronchi and lung, larynx, and GI tract are thought to be neoplasms with at least possible malignant potential and are not called "adenomas", except for endocrine microadenomas of the pancreas. Much of the rationale for not applying the term "carcinoid" to these tumors is related to their biologic behavior. These neoplasms have long been considered to be benign. Indeed, the tumors have a favorable biologic behavior and a good prognosis. Most are cured with excision, and only a relatively few local recurrences have been reported. However, recent studies have shown that, as in the case presented here, late metastases to regional lymph nodes can occur. Four cases of middle ear carcinoids with metastases, including this one, have been reported in the literature to date [2, 3]. Therefore, I agree with Ferlito et al. [3] that these tumors should be considered potentially malignant, and I feel that they truly merit the designation of carcinoid tumor of the middle ear. References Torske KR, Thompson LDR. Adenoma versus carcinoid tumor of the middle ear: a study of 48 cases and review of the literature. Mod Pathol 2002; 15: 543-555. Ramsey MJ, Nadol JB Jr., Pilch BZ, McKenna MJ. Carcinoid tumor of the middle ear: clinical features, recurrences, and metastases. Laryngoscope 2005; 115: 1660-1666. Ferlito A, Devaney KO, Rinaldo A. Primary carcinoid tumor of the middle ear: a potentially metastasizing tumor. Acta Otolaryngol 2006; 126: 228-231.