*Departments of Pathology, Medical College of Wisconsin, Milwaukee, WI †Mayo Clinic, Scottsdale, AZ ∥The MD Anderson Cancer Center, Houston, TX ‡S. Maria della Misericordia General Hospital, Udine, Italy §The Western Galilee Hospital, Naharia, Israel.
Solitary fibrous tumor (SFT) is a ubiquitous neoplasm that arises most commonly from the pleura. SFT arising within lung parenchyma (intrapulmonary SFT) has been rarely reported and is therefore not well recognized. We present a clinicopathologic and immunohistochemical study of 24 cases of primary intrapulmonary SFT. Patients' ages ranged from 44 to 83 years (mean, 58 y). None of the patients had evidence or history of a similar tumor elsewhere. Tumor size ranged from 2.3 to 22 cm (mean, 8.5 cm). On the basis of the degree of cytologic atypia, cellularity, mitotic activity, and areas of necrosis, the lesions were divided into low-grade, intermediate-grade, and high-grade histology. Twenty-one tumors showed the conventional features of SFT of low-grade histology (<5 mitoses per 10 high-power fields), with alternating bands of rope-like collagen flanked by a bland-appearing spindle cell proliferation. Hemangiopericytic, angiofibromatous, and a neural-like plexiform growth pattern were also observed. Five of 21 cases showed an "adenofibromatous" appearance imparted by entrapped normal airspaces at the advancing edges of the lesion. One intermediate-grade tumor showed overall increased cellularity with plump, pleomorphic nuclei, 5 to 10 mitoses per 10 high-power fields, and focal areas of classic SFT. Two cases showed high-grade features at initial presentation, with areas resembling a pleomorphic high-grade sarcoma admixed with foci of conventional, low-grade SFT. Immunohistochemical staining analyses performed in 13 cases showed positivity of the tumor cells for CD34, bcl-2, and CD99 in the majority of cases tested. Clinical follow-up was available in 18 patients, with long-term follow-up (>5 y) in 6. Fourteen (14/18) patients were alive and well without evidence of disease 1 month to 14 years after initial diagnosis. Three patients died of their tumors after 4, 5, and 7 years; in 2 of them the initial tumor was of low-grade histology, but the recurrence/metastases showed a high-grade histology; the third fatal case showed a tumor with high-grade histology at initial diagnosis. One patient with intermediate-grade histology also had chest wall metastases at 5 years but was subsequently lost to follow-up. The results of our study indicate that although tumors with overtly malignant histologic features can be expected to behave as high-grade sarcomas, tumors with bland-appearing morphologic features at presentation may also follow an aggressive behavior. Adequate excision with close clinical follow-up, thus, appears to be the most prudent course of action for the management of primary intrapulmonary fibrous tumors.
"World Health Organization (WHO) classification scheme for soft tissue tumors , the definition of solitary fibrous tumor (SFT) is a ubiquitous mesenchymal tumor of probable fibroblastic type that shows a prominent haemangiopericytoma-like branching vascular pattern. SFTs can be pleural or extrapleural and have been detected in different locations such as in the scalp, orbit, thoracic wall, mediastinum, pericardium, retroperitoneum, abdominal cavity, pelvis, meninges, spinal cord, periosteum, as well as organs such as the lungs, thyroid, salivary glands, liver, gastrointestinal tract, adrenals, prostate, spermatic cord, testes, urinary bladder, and others   . Morphologically, pleural SFTs resemble extrapleural SFTs. "
[Show abstract][Hide abstract] ABSTRACT: The authors report 2 cases of an apparently unpublished stromal tumor of the lung characterized by a predominantly endobronchial growth pattern and benign-appearing clear cells. Both tumors were discovered incidentally in adult patients during routine workups for other medical reasons and treated with lobectomy. On gross inspection there was no evidence of infiltration of the adjacent lung tissue. Microscopically, both lesions featured monotonous oval-shaped to spindle-shaped cells growing in a vaguely nested pattern. The cytoplasm was slightly vacuolated or granular. In 1 case there was a variable admixture with mature fat. Immunohistochemistry was negative for markers of epithelial and stromal differentiation except for vimentin. A focal reaction for CD34 was seen in 1 case. No mutation of coding sequence of VHL gene was seen in one case. Medical follow-up at 1 year was negative for tumor recurrence or metastases. The broad differential diagnosis within the spectrum of stromal lung tumor is discussed. Owing to distinctive microscopic features such as the nesting of clear cells within a vascularized background, both tumors appeared similar to hemangioblastoma, although the expected immunohistochemical profile of the latter was not fully expressed. Because of pattern of growth seen in both lesions we believe that the appellation of endobronchial, hemangioblastoma-like clear cell stromal tumor may be provisionally designed.
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