Solitary fibrous tumorD21.9

Klemperer and Rabin 1931

Rarer (up to now approx. 900 cases can be proven in the literature) primary extracutaneous (pleura, lung) localized, up to 10 cm large, connective tissue tumor with locally aggressive growth as well as recurrence tendency. Metastasis (10% of cases) is possible. In the past, the neoplasm was often confused with a hemangiopericytoma.

In larger series, men and women were equally distributed (Li XL et al. 2017). Mean age at discovery of the tumour: 54 years

Pleura, lung, central nervous system, kidney, prostate, female genitals; more rarely in skin and subcutis of head and neck (then called extrapleural fibrous solitary tumor).

Ultrasound

Computer tomography (CT)

Magnetic Resonance Imaging (MRI)

Positron emission tomography (PET)

Histologically, a patternless pattern with STAT6-, CD34-, CD99- and bcl-2-positive spindle-shaped cell elements is seen. There is a marked similarity to dermatofibrosarcoma protuberans. Frequent deer antler-like branched vessels.

Immunophenotyping provides the crucial criteria for confirming the diagnosis. The SFT is CD34 and vimentin positive with negative failure with antibodies to the various cytokeratins.

Meanwhile, a disease-defining NAB2-STAT6 gene fusion resulting from an intrachromosomal inversion involving 12q13.3 is demonstrated. Derived immunohistochemical evidence of nuclear STAT6 expression has high diagnostic value in distinguishing SFTs from other connective tissue tumors (Vogels RJ et al. 2014; Wilk M et al. 2018).

Surgical resection is considered the curative therapy. In the dermatological field, a histologically controlled three-dimensional excision procedure should be chosen in order to reliably avoid local
recurrences. Chemotherapy is another treatment option.

Certain drugs target vascular endothelial growth factor (VEGF) and other tyrosine kinase signaling pathways. These signaling pathways interrupt the blood supply to the tumor and have recently been used to treat advanced solitary fibrous tumors to slow their progression. Examples of these drugs include bevacizumab (Avastin), sunitinib (Sutent), pazopanib (Votrient) and sorafenib (Nexavar).

Even in benign SFT, recurrences are still observed after periods of several years following complete surgical resection of the primarius. Therefore, lifelong follow-up by CT or MRI is recommended.

1. Ding ZY et al. (2017) Expression and significance of STAT6 in solitary fibrous tumor. Zhonghua Bing Li Xue Za Zhi 46:235-239. https://www.ncbi.nlm.nih.gov/pubmed/28376588

2. Huang SC et al (2019) Solitary fibrous tumor: An evolving and unifying entity with unsettled issues. Histol Histopathol 34:313-334.

3. Ikeda M1 et al (2017) Solitary fibrous tumor of the kidney. Hinyokika Kiyo 63:471-474.
4. Jia Q et al. (2018) Surgical management of spinal solitary fibrous tumor/hemangiopericytoma: a case series of 20 patients. Eur Spine J 27:891-901.
5. Li XL et al. (2017) Solitary fibrous tumor/hemangiopericytoma of central nervous system: a clinicopathologic analysis of 71 cases. Zhonghua Bing Li Xue Za Zhi 46:465-470.
6. Reyhan A (2018) Solitary fibrous tumor of the vagina with potentially malignant features: A Case Report and Review of the Literature. Turk Patoloji Derg 34:186-189.
7. Vogels RJ et al (2014) Solitary fibrous tumor - clinicopathologic, immunohistochemical and molecular analysis of 28 cases. Diagn Pathol 9:224.
8. Wilk M et al (2018) Mesenchymal and neuronal tumors. In: Plewig G et al (eds) Braun-Falco`s dermatology, venereology and allergology. Springer Verlag SS 1887-1919