A giant intrapulmonary solitary fibrous tumor (SFT) was diagnosed through histopathologic examination and immunohistochemical testing in a 57-year-old woman with progressive chest pain, dyspnea, and a hepatic lesion suspicious for metastasis. Despite low-grade histologic features, the tumor demonstrated extensive local involvement, while immunohistochemical findings established the diagnosis following 2 months of unsuccessful empirical antituberculosis treatment.
Investigators described a patient who previously was hospitalized for hypoglycemia, during which a left pleural effusion was incidentally detected. Her medical history included diabetes mellitus, passive smoking exposure, and more than 20 years of employment in a textile factory. Initial chest radiography demonstrated a homogeneous opacity in the left lower lung field with pleural effusion.
The diagnostic evaluation included serial contrast-enhanced computed tomography (CT), core needle biopsy, histopathologic examination, and immunohistochemical testing. These assessments characterized the pulmonary mass, established the diagnosis, and evaluated local extension and possible metastatic spread. Follow-up imaging and pulmonary function testing documented the patient's clinical course following treatment.
Initial CT in July 2025 revealed a left lower lobe mass measuring 14.1 × 15.6 × 12.1 cm. Following more than 5 months without follow-up, repeat imaging demonstrated enlargement of the mass to 11 × 16.5 × 15.2 cm, accompanied by rightward cardiac displacement, atelectasis, pericardial effusion, and minimal pleural effusion. A 3.8-cm hepatic nodule was also identified, raising suspicion for metastatic disease.
Core needle biopsy revealed a low-grade spindle cell neoplasm with 1 to 2 mitoses per 10 high-power fields. Immunohistochemical analysis demonstrated diffuse nuclear STAT6 positivity, partial CD34 positivity, and a Ki-67 proliferation index below 5%. Staining was negative for CK7, desmin, smooth muscle actin, and S100. These findings supported the diagnosis of intrapulmonary solitary fibrous tumor.
Although the low mitotic count and Ki-67 index suggested low-grade histology, the tumor's substantial size and suspected metastatic spread raised concerns regarding aggressive biological behavior. Nuclear STAT6 expression is a highly sensitive and specific marker for solitary fibrous tumors, particularly when distinguishing them from other spindle cell neoplasms.
The patient's earlier hypoglycemia also raised suspicion for Doege–Potter syndrome, a rare paraneoplastic condition associated with solitary fibrous tumors and secretion of insulin-like growth factor2 (IGF-2). However, serum IGF-2 levels were not assessed, preventing confirmation of the syndrome.
Following multidisciplinary evaluation, upfront surgical resection was deferred because of the extent of disease and suspected metastatic spread. The patient subsequently received 6 cycles of doxorubicin, cisplatin, vincristine, and cyclophosphamide. Follow-up CT demonstrated a persistent mass measuring 16.2 × 9.0 × 14.7 cm with suspected pericardial invasion but no mediastinal lymphadenopathy. Pulmonary function testing revealed mild diffusion impairment, with a diffusing capacity of the lungs for carbon monoxide of 67% and preserved spirometry. The patient remained clinically stable despite persistent radiologic findings.
The report has several limitations. As a single-patient case report, the findings cannot establish the diagnostic performance of immunohistochemical markers or the effectiveness of systemic chemotherapy. The hepatic lesion was suspicious for metastasis on imaging but was not histologically confirmed. Additionally, the absence of IGF-2 testing prevented confirmation of Doege–Potter syndrome. Although the patient remained clinically stable following chemotherapy, persistent tumor burden limited conclusions regarding treatment response.
The case highlights the diagnostic challenges associated with giant intrapulmonary solitary fibrous tumors, particularly when nonspecific clinical manifestations coexist with extensive local involvement and possible metastatic disease. The authors emphasized the importance of combining clinical, radiologic, histopathologic, and immunohistochemical findings to establish the diagnosis and guide individualized management.
"This case highlights the importance of integrating clinical, radiological, histopathological and immunohistochemical findings to establish an accurate diagnosis and guide the individualized management of giant intrapulmonary SFT," wrote lead study author Desdiani Desdiani, of the Faculty of Medicine and Nutrition at IPB University in Bogor, Indonesia, and colleagues.
Disclosures: The authors reported no funding or conflicts of interest.
Source: Respirology Case Reports
