Follicular dendritic cell sarcoma of the tonsil: report of a rare case. (Original Article).

Abstract

Follicular dendritic cell tumors are extremely rare. Only 17 cases have been previously described in the literature, and only three of them involved primary tumors of the oral cavity. We describe a new case of the latter, which occurred in a 51-year-old man who sought evaluation for a painless enlargement of his left palatine tonsil. The tonsil was excised, and histologic examination revealed that the tumor was a primary sarcoma that had arisen from the dendritic reticulum cells of the palatine tonsil. Postoperatively, the tumor site was treated with percutaneous irradiation (total dose: 70 Gy). After more than 5 years of follow-up, the patient showed no evidence of recurrence. We also discuss the salient features of the immunohistochemical examination.

Introduction

Nonlymphoid and nonphagocytic follicular dendritic cells are among the accessory cells of the lymphoid system. Follicular dendritic cell tumors are extremely rare; in the recent literature, only 17 cases have been described. (1-6) Primary follicular dendritic cell tumors of the oral cavity are particularly rare, as only three cases have been previously reported in the literature. (2)

The main function of follicular dendritic cells is to trap and present antigens and immune complexes. Follicular dendritic cells are found primarily in germinal centers. They are called dendritic because of their morphology. Follicular dendritic cells may be multinucleate; they have complement receptors and human leukocyte antigen-DR on their surface. They are identified immunohistochemically by their reactivity for CD21 (C3d receptor), CD35 (C3b receptor), Ki-M4p, and Ki-FDRC1p antibodies. (7-9) In 1986, Monda et al (5) confirmed what Lennert (10) suspected as early as 1978 when they first documented the existence of a primary lymph node neoplasm whose features suggested follicular dendritic cell differentiation. Follicular dendritic cell tumors are usually made up of sheets of spindly cells in whorled and storiform arrangements. These cells form syncytia and are characterized by oval nuclei, fine chromatin, distinct nucleoli, and occasional nuclear pseudoinclusions.

In this article, we describe a new case of dendritic reticulum cell sarcoma in the oral cavity--one that arose in the tonsil. We also discuss the special aspects of the diagnosis and treatment of this rare tumor, and we review the pertinent literature.

Case report

A 51-year-old man came to an otolaryngologist for evaluation of a painless enlargement of his left palatine tonsil that he had first noticed several months earlier. He complained that he felt as if a foreign body was obstructing his throat; this feeling was especially noticeable when he swallowed. On examination, his left tonsil was found to be enlarged and indurated, and its upper pole was covered with a gray-white coating. Analysis of fine-needle aspirates obtained from the tonsil revealed that the cell material was normal. A squamous cell carcinoma of the tonsil was suspected.

We took the patient to the operating room for a radical tonsillectomy under general anesthesia. The tonsil was removed along with a small but adequate margin of healthy tissue on all sides of the tumor (figure). Histology of the excised mass revealed that the stratified nonkeratinizing squamous epithelium of the tonsil was normal. Beneath the epithelium, however, we found a lobular tumor that was septated by fibrillar connective tissue. The tumor was made up primarily of spindle-shaped, partially polygonal cells that had indistinct cell borders and polymorphic oval cell nuclei; the nuclei were characterized by mild hyperchromatism and prominent nucleoli. Analysis also detected evidence of numerous mitoses, partial tumor regression, foam cells, and multinucleated giant cells. Nuclear vacuoles were found in some cells. Partially intracytoplasmatic needle-shaped material was seen, and it was positive on periodic acid-Schiff staining. A sparse meshwork of plump reticulin fibers was found between the cells.

Immunohistochemical studies revealed that the spindle-shaped cells expressed vimentin. High-level expression of CD23, low-level expression of pan-leukocyte antigen and S-100 protein, and focal expression of epithelial membrane antigen were observed, as well. Scattered CD2Opositive B lymphocytes were present in the tumor tissue. Immunohistochemistry identified no expression of cytokeratin, actin, desmin, chromogranin, calcitonin, CD34, or HMB-45. On the basis of the Ki-67 index, proliferation activity was approximately 10%. Specific transcripts of in situ hybridization for Epstein-Barr virus (EBV)-encoded RNA were not detected.

Based on these findings, we established the diagnosis of dendritic reticulum cell sarcoma of the tonsil. Subsequent staging procedures (i.e., chest x-ray, ultrasonography of the upper abdominal region, bone scanning, positronemission tomography, and computed tomography of the face and neck) detected no sign of regional or distant metastasis.

In view of the small safety margin associated with the resection of mesenchymal tumors and the potential of malignant mesenchymal soft-tissue tumors for local recurrence, the primary tumor site was irradiated with a total dose of 70 Gy (2 Gy in five treatments per week over 7 weeks). During more than 5 years of follow-up, the patient had not manifested any evidence of recurrence.

Discussion

In 1986, Monda et al became the first to describe a dendritic reticulum cell sarcoma. (5) They reported four cases in which patients had initially been diagnosed as having malignant lymphoma, lymphosarcoma, and metastasizing hemangiopericytoma. Immunohistology, however, was not performed initially to confirm those initial diagnoses; it was not until later that immunohistologic analysis revealed that all four patients did indeed have dendritic reticulum cell sarcoma. Since the initial report by Monda et al, 13 other cases have been described in the international literature. (1-4,6)

When it does occur, dendritic reticulum cell sarcoma is most common in patients who are between the ages of 30 and 50 years; our review of the pertinent literature found that the mean age was 46. (1-6) These tumors have occurred with more or less equal frequency in the two sexes. In the head and neck, these masses were notable for their slow growth and the absence of pain. The lymph nodes of the middle jugular group were involved in most cases. The appearance of a primary tumor in an extranodal site-as occurred in our patient-has rarely been seen. In fact, only three other cases of a primary tumor in the oral cavity have been previously reported. (2)

Histomorphologically, follicular dendritic cell tumors are characterized by high mitotic activity and a spindle-shaped arrangement of cells of isolated necrotic foci. Further tests are required to confirm the diagnosis. In particular, the expression of CD21, CD35, Ki-M4p, and Ki-FDRC1p antibodies must be shown. (1-3,5,6) However, in patients with acquired immunodeficiency syndrome, the expression of CD2l is also suggestive of EBV infection and leiomyosarcoma. (11) For this reason, human immuno-deficiency virus infection and especially EBY infection should be ruled out, as we did in our case.

The differential diagnosis of dendritic reticulum cell sarcoma includes ectopic meningioma, ectopic thymoma, amelanotic malignant melanoma, malignant fibrous histiocytoma, and undifferentiated carcinoma. These tumors can be ruled out by immunohistochemical studies, particularly because the cells of none of these tumors express CD21, CD35, Ki-M4p, or Ki-FDRC1p.

Our review of the available case reports suggests that dendritic reticulum cell sarcomas should be generally considered to be mildly malignant, and the prognosis appears to be good in patients who receive early treatment. In isolated cases, however, tumors were found to pursue an aggressive course and had the potential for local recurrence and distant metastasis, especially to the lungs and liver. (3,5) Histologically, the presence of a large number of necrotic foci appears to be an important indication of a poor prognosis. (1,3,4) Nevertheless, it is not yet possible to reliably predict any outcome because of the paucity of reported cases.

Radical surgical removal of the tumor is the recommended primary treatment for dendritic reticulum cell sarcoma. The regional lymphatic drainage system should be removed only if an imaging test provides evidence of metastasis. (12) Few findings are available on postoperative irradiation. Radiotherapy has been recommended in the pertinent literature for patients who have experienced a local recurrence or metastasis. (12) Nevertheless, even though our patient had no evidence of either, we decided to irradiate the primary tumor site because the safety margin of the excised sarcoma was small.

Acknowledgment

The authors thank Mrs. Barbara Isenberg of the Bundessprachenamt for her assistance in the editing of the manuscript.

References

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From the Department of Otolaryngology--Head and Neck Surgery (Dr. Tisch, Dr. Hengstermann, and Dr. Maier) and the Department of Pathology (Dr. Kraft), Federal Armed Hospital, Ulm, Germany. Dr. von Hinuber is in a group pathology practice in Kempten, Germany.

Reprint requests: Dr. Matthias Tisch, Oberstabsarzt, Abteilung, HalsNasen-Ohren-Heilkunde-Kopf-und Halschirurgie, Bundeswehrkrankenhaus Ulm, Oberer-Eselsberg 40, D-89081 Ulm, Germany. Phone: [phone]; fax: [phone]; e-mail: [e-mail]