Gastroenterol Res

Gastroenterology Research, ISSN 1918-2805 print, 1918-2813 online, Open Access

Article copyright, the authors; Journal compilation copyright, Gastroenterol Res and Elmer Press Inc

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Case Report

Volume 15, Number 5, October 2022, pages 268-277

An Unusual Solitary Fibrous Tumor of the Ischiorectal Region

Figures

Figure 1. Radiological MRI features of solitary fibrous tumor (MRI: October 2018). (a) Coronal T2WI with fat saturation shows a well-defined heterogeneous predominantly low signal intensity right ischiorectal fossa ice-cone shaped mass (white asterisk). (b, c) Pre and post contrast-enhanced coronal T1WI with fat suppression showing homogenous lesion isointense to muscles in pre-contract and avidly enhancing following contrast administration (orange asterisk). MRI: magnetic resonance imaging.

Figure 2. Histological features of solitary fibrous tumors (true cut needle biopsy: October 2018). (a-d) The tumor consists of a haphazard proliferation of short spindle to ovoid cells with banal-looking oval to spindle nuclei, pale eosinophilic cytoplasm, and some collagenized stroma (star), and the hemangiopericytoma-like vascular structures (arrow). The tumor cells are negative for SMA (e) (original magnifications: (a) × 20; (b) × 200; (c) × 400; (d) × 200; and (e) × 200).

Figure 3. Radiological CT features of solitary fibrous tumor (CT: January 2022). (a, b) Contrast-enhanced CT of the pelvis shows a well-defined right ischiorectal fossa oval-shaped mass (white arrow) with progressive contrast enhancement on delayed CT (b). (c) Contrast-enhanced CT coronal reformat shows a well-defined elongated right ischiorectal fossa mass (orange arrow). CT: computed tomography.

Figure 4. Radiological MRI features of solitary fibrous tumor (MRI: January 2022). (a) Coronal T2WI shows right well-defined heterogeneous predominantly low signal right ischiorectal fossa ice cone-shaped mass (white asterisk) upward displacing the right levator ani muscle (yellow arrow) without invasion. (b, c) Pre- and post-contrast-enhanced coronal T1WI with fat suppression show homogenous lesion isointense to muscles in pre-contract and avidly enhancing following contrast administration (orange asterisk). MRI: magnetic resonance imaging.

Figure 5. Gross and histological features of the solitary fibrous tumor (excisional biopsy: January 2022). Gross examination of the mass reveals well-defined, thinly encapsulated mass measuring about 5 × 3.5 × 3 cm (a). Histologic sections reveal cellular spindle cell neoplasm in a collagenous stroma with variable-sized blood vessels having stag-horn vascular morphology (b). The neoplastic cells are ovoid, short, or fusiform spindle-shaped cells with indistinct cell borders, bland looking nuclei, and indistinct nucleoli. They are arranged in short, poorly defined bundles, haphazardly fashion, and patternless pattern. The cells are streamed among the dermal collagens. No mitotic activity was seen. No significant nuclear atypia or necrosis was seen (c, d). The tumor cells are diffusely and strongly positive for CD34, BCL2, and CD99 (e, f, and g, respectively) and are negative for desmin, S100, and pancytokeratin (AE1/AE3) (original magnifications: (b) × 40, (c) × 200, (d) × 400, (e) × 200, (f) × 200, and (g) × 200).

Table

**Table 1.** Previous Studies About Pelvic Solitary Fibrous Tumor
Studies	Age/sex	Anatomic site	Clinical features	Treatment
M: male; F: female; CT: computed tomography.
[14]	Middle-aged	Ischiorectal fossa	Pelvic symptomatology	Resection of the mass
[15]	42/M	Ischiorectal fossa	Rectal mass	Resection of the mass
[16]	80/M	The perineal area close to the anal sphincter	Perineal mass	Resection of the mass
[19]	62/M	Anorectal region, recurrence in perineal region	Anorectal region, recurrence in perineal region	Resection of the mass
[20]	46/F	Pelvic mass displacing the rectum	Doege-Potter syndrome	Resection of the mass
[21]	27/F	Mesorectum	Intraoperative pelvic tumor	Resection of the mass
[22]	72/M	Recurrent malignant tumor, ventral to sacral bone	Intermittent loss of consciousness	Resection of the mass
[23]	64/M	Mass posterior to the bladder and associated with prostate	Lower abdominal pain	Resection of the mass
[24]	34/M	Mass close to the prostate	CT findings suggestive of a prostatic mass lesion	Resection of the mass
[25]	56/F	Mass in the mesorectum	Radiological findings of giant pelvic mass	Resection of the mass
[26]	54/M	Wall of the low rectum	Colonoscopic studies suggestive of rectal mass	Resection of the mass
[31]	33/F	Tumor mass involving the sacral spinal canal and sacral foramen	Lower extremity pain, numbness, and muscle weakness	Resection of the mass
[26]	43/M	Left obturator area	Abdominal pain, appendicitis	Resection of the mass
[27]	49/M	Mass related to the urinary bladder	Difficulty in urination	Resection of the mass
[28]	76/M	Pelvic mass displacing the urinary bladder and rectum	Constipation, abdominal pain, and urine retention	Resection of the mass
[32]	21/F	Mass arising from the serosa of the sigmoid colon	Acute abdominal pain, constipation, and hematochezia	Resection of the mass
[30]	19/F	Mass in the ischioanal fossa	Pelvic pain and bleeding per rectum	Embolization and surgical resection