A dedifferentiated solitary fibrous tumor of the parotid gland: a case report with Cytopathologic findings and review of
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CASE REPORT
Open Access
A dedifferentiated solitary fibrous tumor of the parotid gland: a case report with Cytopathologic findings and review of the literature Chien-Kuan Lee1, Ken-Liao Liu2* and Sheng-Kai Huang2
Abstract Background: Solitary fibrous tumor (SFT) is a ubiquitous mesenchymal neoplasm but it rarely occurs in the parotid gland. The histological features are variable, with the majority having spindle cell morphology and non-specific branching (staghorn) ecstatic vascular pattern. SFT ranges from benign to overtly malignant. Dedifferentiation within SFTs represents an abrupt transition from a well-differentiated component to a high-grade area, the latter most often including poorly differentiated epithelioid/round cell or high-grade spindle cell morphology. To the best of our knowledge, dedifferentiated SFT in the parotid gland has not been previously reported. Case presentation: A 33-year-old woman presented with a soft tissue tumor in the right parotid gland that had been present for 6 months. Fine needle aspiration (FNA) cytology indicated epithelioid morphology in the dedifferentiated component of the tumor, along with metachromatic myxoid matrix. The tumor was initially interpreted as a salivary gland neoplasm of uncertain malignant potential (SUMP).Right partial parotidectomy was performed, and microscopic examination of the resected specimen revealed a malignant spindle cell tumor with a central epithelioid/anaplastic component. The tumor cells were diffusely positive for CD34, STAT-6 and FLI-1, and negative for pan-cytokeratin, CAM5.2, p63, S100 protein, CD31, SMA, and calponin.ERG and Ki67 immunostaining showed an accentuated nuclear staining pattern in the central dedifferentiated area. There was no overexpression of p53 or p16. The patient is currently undergoing regular follow-up and is 11 months postresection with no evidence of recurrence or distant metastasis. Conclusions: Unlike the typical spindle cell morphology of conventional SFTs, malignant SFTs can show areas of dedifferentiation mimicking an epithelial neoplasm. FNA of dedifferentiated SFTs of the parotid gland may show, a combination of atypical epithelioid cells and metachromatic myxoid/collagenous matrix, which is a less emphasized cytological feature of SFT and may lead to misdiagnosis as a more common parotid gland epithelial neoplasm. Keywords: Dedifferentiated solitary fibrous tumor, Parotid gland, FNA, Cytology, ERG
Background Solitary fibrous tumor (SFT) is a mesenchymal neoplasm of presumed fibroblastic origin. Initially described in the pleura by Klemperer and Rabin in 1931 [1], it has also been frequently encountered in extrapleural sites virtually everywhere in the body. Although most SFTs pursue * Correspondence: [email protected] 2 Department of Otorhinolaryngology, Kung Tien General Hospital, Shalu, Taichung, Taiwan Full list of author information is available at the end of the article
a benign clinical course, approximately 12–22% behave aggressively [2]. The 2013 WHO classification of soft tissue tumors define
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