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  Table of Contents    
Year : 2019  |  Volume : 62  |  Issue : 1  |  Page : 189-190
Catechism (Quiz 3)

Department of Surgical Pathology, Tata Memorial Hospital, Parel, Mumbai, India

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Date of Web Publication31-Jan-2019

How to cite this article:
Rekhi B. Catechism (Quiz 3). Indian J Pathol Microbiol 2019;62:189-90

How to cite this URL:
Rekhi B. Catechism (Quiz 3). Indian J Pathol Microbiol [serial online] 2019 [cited 2019 Jul 17];62:189-90. Available from: http://www.ijpmonline.org/text.asp?2019/62/1/189/251267

   Clinical History Top

A 33-year-old male presented with a painful lesion in his index finger. He underwent radiologic imaging followed by a biopsy.

Radiologic findings

Plain radiograph showed a well-defined lytic lesion, showing peripheral ossification, involving the base of the proximal phalanx, with adjacent soft tissues [Figure 1]a.
Figure 1: (a) Plain radiograph showing a well-defined lesion, predominantly involving the soft tissues of the base of phalanx with peripheral ossification. (b) Magnetic resonance imaging showing a well-defined enhancing lesion. (c) Histopathologic findings. Lesion composed of fibroblastic cells in a myxoid stroma with reactive woven bone toward the periphery (H and E, ×200); (d) Fragments of woven bone lined by osteoblasts and osteoclasts within cellular fibroblastic stroma (H and E, ×200)

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Magnetic resonance imaging (MRI) showed a well-defined punched out, mostly a soft tissue lesion, measuring 13 mm × 9.6 mm × 7.5 mm, involving the ventromedial aspect of base of the proximal phalanx. The lesion seemed expanding the volar cortex of the phalanx, scalloping the intact inner cortex, with a well-circumscribed soft tissue extension. It was heterogeneously hyperintense on T2-weighted image (T2WI), fat sat proton density (FSPD) and short tau inversion recovery (STIR) images and isointense on T1WI [Figure 1]b. The radiologic differentials were giant cell tumor and enchondroma protuberans.


  1. What is the diagnosis?
  2. Which category of tumors this entity comes under?
  3. What is the recently described genetic event driving these group of tumors?

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

Answer of Catechism (Quiz 2)


(1) Solitary fibrous tumor. (2) CD34 and STAT6. (3) Low risk.

   Discussion Top

Solitary fibrous tumor (SFT) is defined as mesenchymal tumor of fibroblastic origin, which invariably displays a prominent hemangiopericytoma-like growth pattern and is composed of CD34-positive fibroblastic cells. The earlier term “hemangiopericytoma” has been replaced by a SFT. This tumor can occur at any body site, although commonly identified in the thoracic (pleural-based), head and neck, and other soft tissue sites.[1]

While most SFTs display CD34 immunoexpression, certain cases might be negative. Moreover, CD34 positivity is seen in other tumors, such as a dermatofibrosarcoma protuberans, spindle cell lipoma; certain cases of gastrointestinal stromal tumor and nerve sheath tumors, which constitute as differential diagnoses of SFT in various locations. Synovial sarcoma and malignant peripheral nerve sheath tumors constitute as its other differentials.

Recently, signal transducer and activator of transcription (STAT)-6 has been identified as a single highly sensitive and a specific IHC marker for diagnosing a SFT, and almost a substitute for a specific fusion gene, NAB2-STAT6, which is the “molecular signature” underlying most SFTs.[2],[3]

Although most SFTs are benign (unless classified as malignant), their behavior can be unpredictable.[1] Therefore, a model of risk stratification has been proposed for SFTs.[4] On that basis, the present case is low risk. Therefore, the patient has not been recommended any adjuvant therapy and is recommended a follow-up.

   References Top

Fletcher CD, Bridge JA, Lee JC. Extrapleural solitary fibrous tumour. In: Fletcher CD, Bridge JA, Hogendoorn PC, Mertens F, editors. World Health Organization Classification of Tumours of Soft Tissue and Bone. Lyon: IARC Press; 2013. p. 80-2.  Back to cited text no. 1
Doyle LA, Vivero M, Fletcher CD, Mertens F, Hornick JL. Nuclear expression of STAT6 distinguishes solitary fibrous tumor from histologic mimics. Mod Pathol 2014;27:390-5.  Back to cited text no. 2
Robinson DR, Wu YM, Kalyana-Sundaram S, Cao X, Lonigro RJ, Sung YS, et al. Identification of recurrent NAB2-STAT6 gene fusions in solitary fibrous tumor by integrative sequencing. Nat Genet 2013;45:180-5.  Back to cited text no. 3
Demicco EG, Park MS, Araujo DM, Fox PS, Bassett RL, Pollock RE, et al. Solitary fibrous tumor: A clinicopathological study of 110 cases and proposed risk assessment model. Mod Pathol 2012;25:1298-306.  Back to cited text no. 4

Correspondence Address:
Bharat Rekhi
Dr. Bharat Rekhi, Room No. 818, Department of Surgical Pathology, 8th Floor, Annex Building, Tata Memorial Hospital, Dr E.B. Road, Parel, Mumbai - 400 012
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/IJPM.IJPM_641_18

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