Teaching Case

A 37-year-old male patient presented with an enormous chest mass. It debuted with a slightly painful swelling which grew progressively in two years. It was initially developed in the left breast area and extended afterwards to the lateral aspect of the chest wall.

Enhanced chest CT showed a well-circumscribed solid mass of the anterior and lateral left aspect of the chest wall extending to the abdominal wall. It had lobulated edges and heterogeneous enhancement. Small dots of calcifications were also found in the tumour. There was no bone lysis or intra-thoracic extension.
MRI imaging revealed the precise location of the mass which lay above the latissimus dorsi, the serratus anterior and the external abdominal oblique muscle. No infiltration of surrounding structures was found. The tumour had the same signal as the muscles in T1-weighted imaging and high signal in T2-weighted imaging. Low signal areas in both T1 and T2-weighted imaging were also present. The tumour measured 28 x 20 x 10 cm and was heterogeneously enhanced.
The diagnosis of solitary fibrous tumour was performed after extensive resection and histopathological analysis. Adjuvant radiotherapy was administrated. 12 months after surgery; the patient is alive with no sign of tumour recurrence.

Solitary fibrous tumors (SFT) are uncommon neoplasms of mesenchymal origin that can be benign or malignant [1]. They were first described in the pleura by Klemperer and Rabin in 1931 [2].

These tumors occur mostly in pleura, but a wide spectrum of extra-thoracic sites has been reported, such as the head and neck regions, the abdomen, retroperitoneum, pelvis, and the soft tissues of the extremities. [3]

Extra-pleural malignant SFT, especially those arising from chest wall, represent an exceedingly rare subset of soft tissue neoplasms.

They principally affect adults between the fourth and seventh decades of life with no sex predilection [3].

Clinically, it is a slow-growing, painless, well-delineated exophytic mass; large tumors can cause compression symptoms, while rarely they are the source of para-neoplastic syndromes (i.e. hypoglycemia secondary to insulin-like growth factor). [1]

At ultrasound, SFT are typically hypoechoic, but occasionally, they are heterogeneous. This heterogeneity is likely to be due to areas of myxoid degeneration.[4]
On CT scan SFT can be hypodense or hyperdense compared to muscles. The attenuation is likely to depend upon the amount of collagen content, thus, lesions with abundant collagen appear hyperdense. The presence or absence of calcifications is not necessarily a helpful distinguishing feature. In addition, there is considerable overlap in the type of enhancement at CT, during which 100% of malignant and 60% of benign SFT exhibit heterogeneous enhancement. [4]
At MRI, SFT are usually isointense on T1-weighted images in regards to muscles and variable on T2-weighted images, having what has been described as a “black-and-white-mixed pattern [5]. The presence of rounded or linear low-intensity foci on both T1 and T2-weighted images is attributable to the collagen content, low cellularity, and associated reduced proton mobility. SFT also are vascular tumors that are vigorously enhancing. This combination of these features produces a chocolate chip cookie” appearance, which can help in their diagnosis. [4]

Histologically, SFT are composed of spindle cells within a background of collagen stroma, often in a whorled pattern or patternless [6]. They are highly vascular and have a propensity to undergo myxoid degeneration. The diagnosis is confirmed by characteristic positive immunohistochemical staining for CD34 and negative staining for S-100 [6].

Radical surgical resection represents the gold standard of SFT treatment. There is no evidence of effectiveness of chemotherapic and/or radiotherapic adjuvant treatments [7].

In our case, the CT-scan and MRI features were in accordance with a SFT. Surgical resection associated with adjuvant radiotherapy was considered conclusive.