Otology & Neurotology 37:e185–e186 ß 2016, Otology & Neurotology, Inc.

Temporal Bone Histopathology Case of the Month

Temporal Malignant Solitary Fibrous Tumor Brandon Kamrava, yAbir Mukherjee, zMichael Weaver, and z§Pamela C. Roehm Department of Otolaryngology; yDepartment of Pathology; zDepartment of Neurosurgery; and §Department of Neuroscience, Temple University School of Medicine, Philadelphia, Pennsylvania

A 63-year-old woman presented with nontender swelling anterior to her right ear of 1-month duration. She denied hearing loss and dizziness. A palpable defect was detected in the outer table of the calvarium around the mass. Preoperative imaging demonstrated a 3.8  1.8  6.1 cm enhancing mass of the right pterional calvarium and temporal fossa with central T2 hyperintensity accompanied by midline shift but no invasion of the brain (Fig. 1, A–C). There was erosion of the right temporal calvarium, thinning of the tegmen, and a small focal dehiscence in the roof of the condylar fossa (Fig. 1A). After preoperative embolization (Fig. 1D), the patient underwent resection of the mass and cranioplasty. The tumor had eroded through the calvarium and floor of the middle fossa into the mastoid and epitympanum. On frozen section, the presence of spindle cells was noted. Final pathology demonstrated a spindle cell tumor with a vague storiform pattern, mild-to-moderate nuclear atypia, and focal fibrous bands (Fig. 2). There was significant mitotic activity (4–12/10 HPF) (Fig. 2A) and focal necrosis. There was a storiform cellular pattern and focal fibrous bands. The neoplastic cells were strongly immunoreactive to STAT-6 and vimentin (Fig. 2B); focally positive for CD34, BCL2, and cytokeratins (AE1/AE3, Cam 5.2); and negative for S-100, melan –a, EMA, CD31, calponin chromgranin, desmin, smooth muscle actin, p63, CD 21, CD 35, and TLE. FISH for EWSR1 and SYT breakapart analysis were also negative. The immunomorphologic features of the tumor were diagnostic for malignant solitary fibrous tumor (SFT).

effects, with a slow onset because of a slow growth rate. Meningiomas have a very similar presentation to SFTs, and should be included in the differential diagnosis (1). Histology and immunohistochemistry are necessary for definitive identification of SFTs. A ‘‘patternless pattern’’ of spindled cells is the typical H&E appearance (2). SFTs originate from an inversion of the long arm of chromosome 12 leading to fusion of NAB2 and STAT6 (3). Resulting high levels of STAT6 allow for differentiation of SFTs from similar neoplasms, including meningiomas. Schweizer et al. (1) demonstrated that 100% of meningeal SFTs (n ¼ 25) and 0% of meningiomas (n ¼ 87) produced a strong nuclear signal in STAT6

DISCUSSION SFTs are rare fibroblastic, spindle-cell neoplasms of mesenchymal origin. Although first described in the pleura, 20% are found in the head and neck, typically originating in the dura. Symptoms result from mass FIG. 1. A, Computed tomography of head, bone windows, demonstrating temporal bone and calvarial erosion and thinning (arrowheads) by large temporal mass (asterisk). B, T1-weighted MRI with gadolinium demonstrating large temporal mass (asterisk). C, T2-weighted coronal MRI showing central T2 hyperintensity within large right temporal mass (arrow). D, Angiogram before embolization of temporal mass demonstrating tumor blush (arrow). MRI indicates magnetic resonance imaging.

Address correspondence and reprint requests to Pamela C. Roehm, M.D., Ph.D., Department of Otolaryngology–Head and Neck Surgery, Temple University School of Medicine, 3509 N. Broad Street, 6th Floor Boyer Pavilion, Philadelphia, PA 19140, U.S.A.; E-mail: [email protected] The authors disclose no conflicts of interest.


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B. KAMRAVA ET AL. malignant histopathological features (5). SFTs of the head and neck and central nervous system have rarely been reported to metastasise (2,4,5). Five-year survival rates are excellent. Over 90% in patients with head and neck who have had complete resection of solitary fibrous tumors (including malignant and nonmalignant forms) with negative margins will survive more than 5 years (5). Intracranial tumors have a lower 5-year survival rate, which is strongly dependent on tumor location, initial size, and recurrence (4).

FIG. 2. A, Hematoxylin and eosin stained section of the temporal mass at 40 magnification, demonstrating spindle cell cellular morphology and multiple mitotic figures (arrowheads). B, Immunostained section of the tumor showing diffuse cytoplasmic immunoreactivity to antivimentin antibody.

immunohistochemistry. SFTs also express CD34, Bcl2, CD99, and vimentin, and are negative for actin, desmin, S100 protein, epithelial membrane antigen, and low weight cytokeratins (2). Malignancy of these tumors is determined on the basis of size, mitotic activity (>4/10HPF), presence of necrosis, increased cellularity, nuclear pleomorphism, and stromal infiltration beyond the pseudocapsule (2). Complete tumor resection is the primary mode of treatment, with some advocating adjuvant radiation for malignant pathology. Total tumor resection is considered the strongest prognostic determinant of recurrence (2,4,5). Other factors affecting recurrence are tumor size and presence of

REFERENCES 1. Schweizer L, Koelsche C, Sahm F, et al. Meningeal hemangiopericytoma and solitary fibrous tumors carry the NAB2-STAT6 fusion and can be diagnosed by nuclear expression of STAT6 protein. Acta Neuropathol 2013;125:651–8. 2. England DM, Hochholzer L, McCarthy MJ. Localized benign and malignant fibrous tumors of the pleura. A clinicopathologic review of 223 cases. Am J Surg Pathol 1989;13:640–58. 3. Mohajeri A, Tayebwa J, Collin A, et al. Comprehensive genetic analysis identifies a pathognomonic NAB2/STAT6 fusion gene, nonrandom secondary genomic imbalances, and a characteristic gene expression profile in solitary fibrous tumor. Genes Chromosomes Cancer 2013;52:873–86. 4. Chen H, Zeng X-W, Wu J-S, et al. Solitary fibrous tumor of the central nervous system: A clinicopathologic study of 24 cases. Acta Neurochir (Wien) 2012;154:237–48. 5. Ganly I, Patel SG, Stambuk HE, et al. Solitary fibrous tumors of the head and neck: A clinicopathologic and radiologic review. Arch Otolaryngol Head Neck Surg 2006;132:517–25.

Otology & Neurotology, Vol. 37, No. 5, 2016

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Temporal Malignant Solitary Fibrous Tumor.

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