Track: Case Reports

Abstract:

Solitary fibrous tumor (SFTs) is a rare fibroblastic soft tissue neoplasm characterized by a prominent thin-walled vasculature and NAB2:STAT6 gene fusion. We present two highly unusual cases of SFT with distant cutaneous metastasis. The first case was a 51 y/o woman who was initially diagnosed with SFT, (low risk category) of left hip. The patient underwent resection and adjuvant radiation therapy in 2012 and developed extensive metastatic disease involving scalp, spine, lung, liver, lymph nodes, adrenal, kidney and muscle after 12 years of initial diagnosis. The second case is a 65 y/o man who was diagnosed with malignant SFT of lung and pleura and treated with resection and adjuvant chemotherapy in 2021. He developed a chin nodule after 4 years and subsequently developed liver and lung metastasis and eventually died of disease. Both cutaneous tumors were treated by resection and exhibited morphologic features of malignant SFT including marked cytological atypia, increased mitosis and necrosis. Immunohistochemistry confirmed the diagnosis, with diffuse nuclear STAT6 positivity. Molecular analysis of both cutaneous lesions showed the presence of TERT promoter mutation as a common finding in addition to p53 mutation, FGFR1 mutation and CDKN2A, CDKN2B loss. Although most SFTs follow an indolent course, a subset may recur, or present with local or distant metastasis, often years after the initial diagnosis. Malignant behavior in SFTs remains difficult to predict. Cutaneous metastasis of SFTs is extremely rare. Awareness of this potential is crucial for accurate diagnosis and tailoring appropriate clinical management.

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Sneha Datwani