| Abstract|| |
Solitary fibrous tumor/hemangiopericytoma (SFT/HPC) is a rare primary central nervous system (CNS) tumor, included in the World Health Organization (WHO) 2016 classification. Very few cases have been described in the literature so far, especially the infantile type. It is a mesenchymal tumor of the fibroblastic type, characterized by the fusion of NAB 2 and STAT 6 genes. A 10-month-old boy presented to our neurosurgery department with complaints of increasing head circumference since 1 month of age. The magnetic resonance imaging (MRI) showed a space-occupying lesion measuring 8.2 cm × 7 cm × 6.9 cm in the fronto-temporo-parietal region with a clinical diagnosis of glioma/atypical teratoid rhabdoid tumor (ATRT). The microscopy revealed a spindle cell tumor arranged in a patternless pattern with variable cellularity, increased mitosis, and areas of coagulative necrosis. The immunohistochemistry showed vimentin, CD 34, STAT6, CD99 positivity whereas Glial fibrillary acidic protein, Epithelial membrane antigen, and S-100 negativity. Hence, a diagnosis of anaplastic SFT/HPC (grade-III) was rendered. The patient improved after gross total resection (GTR). The primary intracranial congenital SFT/HPC are extremely rare, often a clinico-radiologically misdiagnosed entity. Thus, the immunohistochemistry/molecular study in addition to histology is mandatory for accurate diagnosis.
Keywords: Congenital, gross total resection, hemangiopericytoma, infantile, intracranial tumor, solitary fibrous tumor, STAT6
|How to cite this URL:|
Debahuti M, Anasuya L, Chandra DR, Prateek D. Infantile (congenital) anaplastic intracranial solitary fibrous tumor/hemangiopericytoma—A case report with brief literature review. Indian J Pathol Microbiol [Epub ahead of print] [cited 2023 Jan 29]. Available from: https://www.ijpmonline.org/preprintarticle.asp?id=345890
| Introduction|| |
Solitary fibrous tumor/hemangiopericytoma (SFT/HPC) included in the World Health Organization (WHO) classification of the central nervous system (CNS) tumors (2016) are rare non-meningothelial neoplasm of mesenchymal origin showing histological, immunohistochemical, and molecular similarities. Initially described as a primary neoplasm of the mediastinum and visceral pleura, are also reported in the extracranial sites like the head and neck, liver, thyroid, pericardium, peritoneum, and orbit but are rarely seen in the CNS. The primary SFT/HPC involving the CNS was first reported in 1996 by Carneiro et al. and the rarity is attributed to a paucity of the connective tissue elements.
| Case Report|| |
A 10-month-old boy presented with a swelling over the fronto-temporo-parietal region with irritability and feeding difficulty, which was noticed by the parents at 1 month and was gradually increasing in size since then, with features of increased intracranial tension. The magnetic resonance imaging (MRI) revealed heterogenous T1, T2 signals with an 8.2 cm × 7 cm × 6.9 cm intensely enhancing the space-occupying lesion in the fronto-temporo-parietal region which is partially intraventricular (frontal horn and body of the left lateral ventricle) and partially extraaxial with central necrosis [Figure 1]a. There was a midline shift of 10.9 mm, subfalcine herniation toward the right, and moderate dilatation of the lateral ventricles. Intraoperatively, it was an intraaxial, solid cystic, firm to hard, minimally vascular partly encapsulated tumor with dural adherence. The tumor was removed in piecemeal by gross total resection (GTR) with the clinico-radiological impression of glioma/atypical teratoid rhabdoid tumor (ATRT). Intraoperatively, the tumor was sent for squash cytology, which revealed spindle cells with variable cellularity in a predominant myxoid background, and a diagnosis of chondroid soft tissue tumor was made [Figure 2].
|Figure 1: (a) MRI showing 8.2 cm × 7 cm × 6.9 cm space occupying lesion in the left fronto-temporo-parietal region; (b) Follow-up CT scan at 7 months showing no residual tumor or absence of recurrence|
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|Figure 2: Squash cytology showing spindle cells in a myxoid background (DiffQuik, 400X)|
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Gross examination showed multiple fragments of grayish-white tissue together measuring 12 cm × 10 cm × 4 cm. The cut section was firm to hard, uniform with mucinous areas [Figure 3].
|Figure 3: Grossly, the tumor having a tan white appearance with myxoid cut surface|
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The microscopic examination revealed a well-circumscribed tumor comprising of cells arranged in alternate hypo- and hypercellular patterns having spindle to ovoid nuclei with moderate nuclear atypia, inconspicuous nucleoli, and increased mitosis (>7/10 HPF). The cells were arranged in bundles, fascicles, and storiform patterns with intervening staghorn blood vessels, large areas of geographic necrosis and myxoid change, compressing glial tissue, and dural elements [Figure 4]a. The reticulin stain showed strong diffuse positivity around the individual cells [Figure 4]b. The immunohistochemistry was done and the tumor cells showed positivity for vimentin, CD34, BCL2, CD99, INI-1, and strong nuclear positivity for STAT-6 whereas the GFAP and S100 were negative, excluding the glioma. Malignant peripheral nerve sheath tumor (MPNST) and ATRT [Figure 4]c and [Figure 4]d. The Ki67 labeling index was 20%. With these results, the diagnosis of anaplastic SFT/HPC (WHO grade III) was made.
|Figure 4: (a) Photomicrograph showing patternless arrangement of spindle cells with fine vasculature and myxoid areas (Hematoxylin and Eosin, 400X); (b) Photomicrograph showing prominent reticulin fibers around the tumor cells (Reticulin, 400X); (c) Photomicrograph showing membranous and cytoplasmic positivity for CD34 in the tumor cells (IHC, 400X); (d) Photomicrograph of immunohistochemical nuclear expression for STAT-6 in the tumor cells (IHC, 400X)|
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Postoperatively, the patient was observed in the intensive care unit for 24 h, received antibiotics and antiepileptics, and was discharged on the 7th post-operative day. Radiation was not considered as the baby was only 10 months old. On follow-up after 7 months, the patient was asymptomatic and the CT scan showed no recurrence or residual tumor [Figure 1]b.
| Discussion|| |
Primary intracranial SFT/HPC most commonly affects adults in the fourth to fifth decades of life with a slight male preponderance. Most tumors are dura-based and supratentorial occurring commonly in the skull bone, parasagittal, and falcine locations.
Radiologically, it shows heterogenous enhancement due to the combination of the hypercellular areas and fibrotic hypocellular areas. This is referred to as the yin-yang sign in some literatures. They are frequently misdiagnosed as neurofibroma, fibrous meningioma, malignant fibrous histiocytoma, and fibrosarcoma on MRI.
The characteristic histologic pictures of SFT include well-circumscribed tumors showing spindle cells in a patternless pattern, hemangiopericytomatous areas, thick strands of collagen with alternate hyper- and hypocellular areas. The various malignant features include increased cellularity, high mitosis, and necrosis. Based on the cellularity and mitosis (≤5 vs. >5/10 HPF), the WHO has graded the tumor into grades I, II, and III. Grade I tumors are hypocellular, collagenized with classic SFT phenotype. Grades II and III show HPC phenotype and are defined by the mitotic count ≤5 or >5/10 HPF, with or without necrosis. The grade I tumor is considered benign and treated by GTR. The grade III tumor is considered malignant, said to have a high recurrence rate, and can develop extracranial metastasis to the bone, lungs, and liver. Both grades II and III may need adjuvant chemotherapy and radiotherapy with surgery. The Ki67 index was high in our case but it varies according to different studies depending on the grade. The histological differentials include fibrous meningioma, MPNST, monophasic synovial sarcoma as well as myxofibrosarcoma.
Meningioma, especially the atypical and anaplastic type, can be distinguished by a strong reactivity for EMA which is absent in HPC/SFT. MPNST can share morphological pictures of HPC/SFT like alternate - and hypercellular areas, myxoid change, geographic necrosis, and increased mitosis. But it is distinguished by positivity for S100 and negativity for CD34, STAT6, and CD99.
Myxofibrosarcoma are distinguished by cells showing lobulated arrangement, conspicuous nucleoli, occasional multinucleated giant cells, predominant myxoid, granular to filamentous background, and absence of thick collagen bundles along with negativity for CD99 and BCL2, though vimentin, and CD34 are positive.
Hence, a thorough Immunohistochemistry (IHC) workup is needed as the WHO highlights that the nuclear expression STAT-6 IHC or molecular confirmation of NAB2-STAT6 fusion is mandatory for the diagnosis of SFT/HPC.
Congenital CNS tumors are exceedingly rare with an incidence of 0.34 per million births. Congenital intracranial SFT/HPC is still rarer and the literature search currently reports only 20 cases to date. The cases reported before the year 2016 were classified as either SFT or HPC depending on the grade.
The oldest of all was recorded in 1954 and only a few cases have been added since then. The last reported case was in 2018 where a 10-day-old female presented with a large intracranial tumor with necrosis and high mitotic activity, similar to the present case. Only subtotal resection (STR) was possible in that case and on a 3-year follow-up, the patient showed a residual neurological deficit. GTR is considered as the main modality of treatment whenever possible., No evidence of the recurrence was seen in the follow-up of 1 month to 5 years, where complete resection was feasible., Chemotherapy has been considered for a few cases either as the initial treatment to facilitate the gross total resection or after the initial therapy in case of incomplete resection or recurrence. Radiotherapy (RT) is also considered as an option for primary or adjuvant therapy. However, the long-term safety was questioned. Overall, the prognosis for HPC/SFT was considered favorable, especially in pediatric tumors as they are usually of low grade.
| Conclusion|| |
HPC/SFT are rare tumors in the CNS, especially the infantile/congenital type. They are also peculiar in their biological behavior and many behave in a benign way if the GTR is achieved catering to a favorable clinical outcome. Careful radiological and histopathological examinations with immunohistochemistry and/molecular study can give an accurate diagnosis. However, more studies with long-term surveillance are needed for the evaluation of different therapeutic options and prognoses, especially for the malignant (grade III) tumors of the infantile type.
Informed written consent was obtained from the parents of the child before biopsy and ethical clearance/no objection certificate has been obtained from the institutional ethical committee for publication of the case report.
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Conflicts of interest
There are no conflicts of interest.
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Assistant Professor, Department of Pathology, IMS and SUM Hospital, Bhubaneswar - 769 004, Odisha
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]