Granular cell tumor of the parotid: A case report and literature review.
Granular cell tumors are relatively uncommon soft tissue lesions that originate in Schwann's cells. Although these tumors can occur at any site, their presence in the parotid gland is very unusual. This article describes one such case in a 48-year-old woman, followed by a brief review of the literature on this subject.
Granular cell tumors are uncommon benign tumors. since their original description by Weber in 1854  and Abrikossoff's widely quoted publication of 1926,  more than 1,200 cases have been reported.  Granular cell tumors usually manifest as asymptomatic, slow-growing, smooth, solitary nodules, which are subcutaneous, intradermal, or submucosal. Multiple satellite nodules occur in 10 to 15% of all cases.  Granular cell tumors can arise at any anatomic site; the three most common sites are the head and neck (especially the tongue), chest wall, and arm. [4,5] The presence of a granular cell tumor in the parotid gland is extremely rare, as only 11 other cases have been reported in the literature. [3-13] In this article, we describe a new case of a parotid granular cell tumor, and we provide a brief review of the literature.
A 48-year-old woman came to us with a right parotid gland swelling that was causing her discomfort. She had previously been treated for chronic sialadenitis with a sialodochoplasty and a dilation of Stensen's duct.
On physical examination, a firm, tender, 1.5-cm mass was palpated inferior to the angle of the mandible. No facial nerve deficits were noted. Magnetic resonance imaging revealed the presence of a 1.5-cm right parotid mass with low Tl and T2 signal characteristics (figures 1 and 2). Imaging with gadolinium showed a diffuse enhancement of the right parotid and less definition of the tumor (figure 3).
The patient underwent a near-total parotidectomy and facial nerve dissection with a facial nerve monitor. The tumor was removed both superficially and deep to the nerve. The patient experienced transient paresis of the lower branches of the facial nerve that resolved during the ensuing 3 months.
The specimen submitted to pathology contained a white, fibrous, and firm nodule that measured 1.5 x 1.0 x 0.8 cm. Microscopically, the tumor contained diffuse nests and cords of cells with abundant easinophilic granular cytoplasm. The tumor infiltrated dense connective tissue and salivary gland lobules (figure 4). Immunohistochemical studies showed that the cells were positive for S-100 and negative for pancytokeratin and muscle-specific actin. The immunophenotype supported the diagnosis of a granular cell tumor.
The origin of granular cell tumors is uncertain. They were initially thought to arise from skeletal muscle because of their cytologic resemblance to myocytes.  Others have postulated that there might be a fibroblastic, histiocystic, or undifferentiated mesenchymal cell origin. [7,14,15] More recent studies suggest a derivation from Schwann's cells. Kurtin and Bonin reported that the monoclonal antibody KP- 1, which recognizes the lysosome-associated glycoprotein CD68, reacts positively with schwannomas and granular cell tumors but not with ganglioneuromas, ganglioneuroblastomas, neurofibromas, and carcinoid tumors.  Similarly, granular cell tumors cytoplasmically stain for S-100 protein, are closely associated with nerves, and are often present in distal nerve trunks; all of these characteristics support a Schwann's cell origin.  This tumor is also known by other names (e.g., granular cell myoblastoma), but the uncertainty of its origin has perpetuated the term granular cell tumor. 
Granular cell tumors have been found throughout the body. They most frequently involve the head and neck-- particularly the oral cavity, especially the tongue. [4,5] They usually manifest as small, nontender, solitary lesions. [4,5] Their histologic features allow for easy diagnosis. These tumors are made up of polygonal cells that feature eosinophilic granular cytoplasm and small nuclei.  They often develop between the second and sixth decades of life, more often in women than men.  A familial tendency has been observed.  Although most tumors are benign, rare malignant variants have been reported.  Rapid growth and a large size combined with histologic findings of mitotic figures, cellular and nuclear pleomorphism, necrosis, wide cellular sheets, and a spindle-cell structure increase the likelihood of malignancy. 
The treatment of choice is radical resection with clear surgical margins. Radiation and chemotherapy are not advised because of the tumor's high degree of resistance.  Complete resection is considered curative. Even when negative margins are not obtained, the prognosis is still favorable.  To rule out late recurrences, patients should be followed with an annual physical examination.
(1.) Weber CO. Anatomische Untersuchung einer hypertrophischen Zunge nebst Bemerkungen uber die Neubildung quergestreifter Muskelfasem. Virchows Arch A Pathol Anat 1854;7:115-25.
(2.) Abrikossoff A. Uber Myome ausgehend von der quergestreifter wilikurlichen Musculature. Virchows Arch A Pathol Anat 1926;260:215-33.
(3.) McDaniel RK. Benign mesenchymal neoplasms. In: Ellis GL, Auclair PL, Gnepp DR. eds. Surgical Pathology of the Salivary Glands. Philadelphia: W.B. Saunders, 1991:489-513.
(4.) Said-Al-Naief N, Ivanov K, Jones M, et al. Granular cell tumor of the parotid. Ann Diagn Pathol 1999;3:35-8.
(5.) Curtis BV, Calcaterra TC, Coulson WF. Multiple granular cell tumor: A case report and review of the literature. Head Neck 1997;19:634-7.
(6.) Carinci F, Marzola A, Hassanipour A. Granular cell tumor of the parotid gland. A case report. Int J Oral Maxillofac Surg 1999;28:383-4.
(7.) Lack EE, Worsham GF, Callihan MD, et al. Granular cell tumor. A clinicopathologic study of 110 patients. 3 Surg Oncol 1980; 13:301-16.
(8.) Jones JK, Kuo TT, Griffiths CM, Itharat S. Multiple granular cell tumor. Laryngoscope 1980;90: 1646-51.
(9.) Mullins GM, Magner JW. Multiple granular cell myoblastomas--a case report. Ir Med J 1984;77:286-7.
(10.) Nielsen M, Thomsen J, Albrechtsen R, Bak-Pedersen K. Granular cell myoblastoma in the parotid gland. J Laryngol Otol 1979;93:943-8.
(11.) Nussbaum M, Haselkorn A. Granular-cell myoblastoma in parotid gland. N Y State J Med 1972;72:2887-8.
(12.) Seifert G, Miehlke A, Haubrich J, et al. Nonepithelial salivary tumors. In: Siefert G, ed. Diseases of the Salivary Glands: Pathology, Diagnosis, Treatment, Facial Nerve Surgery. Stuttgart, New York: Georg Thieme Verlag, 1986:286-301.
(13.) de Sequeira OF, Marcos-Martins O, Hercules HC, dos Santos JL. [Multiple myoblastoma with bronchial, lingual and parotid locations]. Hospital (Rio J) 1970;77:1179-95.
(14.) Batsakis JG, Manning JT. Soft tissue tumors: Unusual forms, Otolaryngol Clin North Am 1986;19:659-83.
(15.) Regezi JA, Batsakis JG, Courtney RM. Granular cell tumors of the head and neck. J Oral Surg 1979:37:402-6.
(16.) Kurtin PJ, Bonin DM. Immunohistochemical demonstration of the lysosome-associated glycoprotein CD68 (KP-1) in granular cell tumors and schwannomas. Hum Pathol 1994;25:1172-8.
|Printer friendly Cite/link Email Feedback|
|Comment:||Granular cell tumor of the parotid: A case report and literature review.|
|Author:||Vernose, Gerard V.|
|Publication:||Ear, Nose and Throat Journal|
|Article Type:||Brief Article|
|Date:||Jul 1, 2001|
|Previous Article:||Superficial leiomyosarcoma of the head and neck: Case report and review of the literature.|
|Next Article:||Nasal T-cell lymphoma: Case report and review of diagnostic features.|