A case of solitary fibrous tumor arising from the palatine tonsil.
Solitary fibrous tumor (SFT) is a distinctive, relatively uncommon soft-tissue neoplasm that usually arises from the pleura. It occurs at various sites; head and neck lesions are very rare. While most of these tumors have a benign course, a small number have malignant potential. We describe a rare case of SFT arising from the left palatine tonsil in a 66-year-old Japanese woman. The mass was completely resected. Immunohistochemical studies were strongly positive for CD34 and bcl-2, mildly positivefor phosphorylated protein kinase B and phosphorylated extracellular signal-regulated kinase 1/2, and negative for platelet-derived growth factor receptor alpha and p53. These findings suggested that this tumor was benign. The patient showed no evidence of recurrence during 2 years of follow-up. We believe that the candidate prognostic marker should be checked to distinguish malignant from benign SFTs.
Solitary fibrous tumor (SFT) is a distinctive, relatively uncommon soft-tissue neoplasm that usually arises from the pleura. (1) The presence of these tumors has also been reported in a number of extrapleural sites such as the lung, mediastinum, and meninges. (2) SFTs are rare in the head and neck region; reported locations have included the infratemporal fossa, (3) the parapharyngeal space, (4) the nose and paranasal sinuses, (5) the thyroid gland, (6) and the palatine tonsil. (7)
Although SFTs are usually slowly growing tumors associated with a favorable prognosis, their biologic behavior is not always predictable, and a small number of malignant cases have been reported. (2,8) Some morphologic features are known to be associated with aggressive clinical behavior. (8,9) Complete resection is universally accepted as the first line of treatment.
In this article, we report a case of SFT of the palatine tonsil, and we review the literature regarding the clinicopathologic characteristics related to patient outcomes.
A 66-year-old Japanese woman presented with a 3-month history of odynophagia and a foreign-body sensation in the throat. Physical examination revealed the presence of a large mucosa-covered mass on the left side of the oropharynx.
Computed tomography (CT) demonstrated a heterogeneously enhancing mass in the left palatine tonsil. Magnetic resonance imaging (MRI) showed that the lesion was clearly circumscribed, demonstrating homogeneous hypo- and isointense signals on T1-weighted imaging (figure 1, A) and heterogeneous high-signal intensity on T2-weighted imaging (figure 1, B). The tumor exhibited heterogeneous enhancement on gadolinium-contrast T1-weighted MRI except for the central part of the tumor (figure 1, C). The mass was radiologically diagnosed as a mesenchymal tumor-either a schwannoma, paraganglioma, or SFT.
The patient was taken to the operating room, and a transoral approach was used for resection. Since no adhesions were present, the tumor was easily removed along with the palatine tonsil (figure 2, A). The safety margin was determined by frozen-section analysis. The tumor was firm, it measured 44 x 35 x 32 mm, and its surface was macroscopically smooth and clearly identified with a negative surgical margin (figure 2, B).
Histopathologic analysis revealed that the tumor was composed of closely packed, spindle-shaped to round cells, and scattered collagenous deposition (figure 3, A). In some areas, necrosis and keloid-type deposition were observed (figure 3, B). There was moderate pleomorphism, occasional mitoses, and prominent vascularity with a hemangiopericytoma-like pattern.
Immunohistochemically, the tumor was strongly positive for CD34 (figure 4, A) and bcl-2 (figure 4, B), mildly positive for phosphorylated protein kinase B (pAKT) and phosphorylated extracellular signal-regulated kinase 1/2 (pERK 1/2), and negative for pan cytokeratin(AEl/AE3),EMA, platelet-derived growth factor receptor (PDGFR) alpha and p53.
Given the histomorphologic and immunohistochemical profile, the diagnosis of SFT was made. The patient's postoperative course was uneventful, and she experienced no surgical morbidity. No postoperative radiotherapy was administered.
At 2 years of clinical follow-up, the patient exhibited no signs of locoregional recurrence or distant metastasis.
SFTs are rarely seen in the palatine tonsil. (7) Pathologically, these tumors often are made up of narrow cords of cells interspersed with thick bundles of collagen (the "patternless pattern") and admixed with (1) an area exhibiting a prominent hemangiopericytoma-like and angiofibroma-like appearance and (2) a neural-type fascicular area with wavy nuclei and an occasional herring-bone formation. (1) Most SFTs are positive for CD34, a transmembrane cell surface glycoprotein described as a marker for human hematopoietic stem cells, (10,11) and bcl-2, a 26-kD protein associated with prolonged cell survival due to inhibition of apoptosis. (12) Our patient's tumor was strongly positive for CD34 and bcl-2.
While most SFTs have a benign course, a small number are associated with invasion, recurrence, and metastasis. (2,8) Features that have been associated with local or distant recurrence include high cellularity, mitotic activity, nuclear pleomorphism, and necrosis. (8,13) However, it is not possible to predict a tumor's behavior on the basis of histologic criteria alone. Therefore, several attempts have been made to find a candidate prognostic marker--that is, a possible biomarker than can be used to distinguish malignant from benign SFTs. In borderline cases, assessment of the frequency of proliferating cells that express Ki-67 can be helpful in identifying malignant potential. (14)
Yokoi et al wrote that immunoreactivity to CD34 might be lost in high-grade malignant SFTs and that the expression of p53 protein might be related to malignant clinical behavior and histologic features. (14) Immunohistochemistry has frequently detected the expression of PDGFR[alpha] and PDGFR(3 in SFT, although missense mutations have been rare. (13) Furthermore, a large number of studies have demonstrated that important signaling pathway molecules, such as pAKT and pERK 1/2, are strongly positive in many kinds of malignant tumors. Our patients tumor was strongly positive for CD34 and bcl-2, mildly positive for pAKT and pERK 1/2, but negative for PDGFRa and p53, meaning that there were few findings to suggest that this tumor was malignant.
Our patient's tumor featured a benign course and no evidence of recurrence. Although large studies would be necessary to find significant markers for malignant SFT, we believe that the candidate prognostic marker should be checked to distinguish malignant from benign SFTs.
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Takeharu Kanazawa, MD, PhD; Kozue Kodama, MD; Mitsuhiro Nokubi, MD, PhD; Kazuo Gotsu, MD; Akihiro Shinnabe, MD; Masayo Hasegawa, MD; Gen Kusaka, MD, PhD; Yukiko Iino, MD, PhD
From the Department of Otolaryngology-Head and Neck Surgery (Dr. Kanazawa, Dr. Kodama, Dr. Shinnabe, Dr. Hasegawa, and Dr. Iino), the Department of Pathology (Dr. Nokubi), and the Department of Neurosurgery (Dr. Kusaka), Jichi Medical University, Saitama Medical Center, Saitama City, Japan; and the Department of Otolaryngology, Hasuda Hospital, Hasuda, Japan (Dr. Gotsu). The case described in this article occurred at the Saitama Medical Center.
Corresponding author: Takeharu Kanazawa MD, PhD, Department of Otolaryngology-Head and Neck Surgery, Jichi Medical University, Saitama Medical Center, 857-1 Amanuma, Omiya, Saitama City, Saitama, 330-8503 Japan. Email: email@example.com
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|Title Annotation:||ORIGINAL ARTICLE|
|Author:||Kanazawa, Takeharu; Kodama, Kozue; Nokubi, Mitsuhiro; Gotsu, Kazuo; Shinnabe, Akihiro; Hasegawa, Mas|
|Publication:||Ear, Nose and Throat Journal|
|Article Type:||Case study|
|Date:||Mar 1, 2015|
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