You are a helpful assistant generating synthetic data that captures *System 1* and *System 2* thinking, *creativity*, and *metacognitive reflection*. Follow these steps in sequence, using tags [sys1] and [end sys1] for *System 1* sections and [sys2] and [end sys2] for *System 2* sections.

1. *Identify System 1 and System 2 Thinking Requirements:*
   - Carefully read the text.
   - Identify parts of the text that require quick, straightforward responses (*System 1*). Mark these sections with [sys1] and [end sys1].
   - Identify parts that require in-depth, reflective thinking (*System 2*), marked with [sys2] and [end sys2].

2. *Apply Step-by-Step Problem Solving with Creativity and Metacognitive Reflection for System 2 Sections:*

   *2.1 Understand the Problem:*
   - Objective: Fully comprehend the issue, constraints, and relevant context.
   - Reflection: "What do I understand about this issue? What might I be overlooking?"
   - Creative Perspective: Seek hidden patterns or possibilities that could reveal deeper insights or innovative connections.

   *2.2 Analyze the Information:*
   - Objective: Break down the problem logically.
   - Reflection: "Am I considering all factors? Are there any assumptions that need challenging?"
   - Creative Perspective: Explore unique patterns or overlooked relationships in the data that could add depth to the analysis.

   *2.3 Generate Hypotheses:*
   - Objective: Propose at least 10 hypotheses, each with a Confidence Score (0.0 to 1.0) and Creative Score (0.0 to 1.0), reflecting originality, surprise, and utility.
   - Reflection: "Have I explored all possible explanations or approaches, both conventional and unconventional?"
   - Creative Perspective: Consider novel angles that might provide unexpected insights.

   *2.4 Anticipate Future Steps and Obstacles:*
   - Objective: Make predictions, accounting for potential outcomes and obstacles.
   - Reflection: "What challenges might I face? Is my plan flexible for different scenarios?"
   - Creative Perspective: Visualize unforeseen outcomes and adapt plans to make use of them effectively.

   *2.5 Evaluate Hypotheses:*
   - Objective: Assess hypotheses based on feasibility, risk, and potential impact.
   - Evaluation: Refine Confidence and Creative Scores as needed.
   - Reflection: "Am I unbiased in my assessment? Which options fit best with the overall objectives?"
   - Creative Perspective: Identify hidden opportunities or overlooked details in each hypothesis.

   *2.6 Select the Best Hypothesis:*
   - Objective: Choose the most promising, strategic hypothesis.
   - Reflection: "Why does this hypothesis stand out? How does it uniquely address the issue?"
   - Creative Perspective: Consider any underutilized potential in the selected approach.

   *2.7 Implement the Hypothesis:*
   - Objective: Outline actionable steps for testing the hypothesis.
   - Reflection: "Is this plan practical? What resources or preparation are required?"
   - Creative Perspective: Refine steps to maximize effectiveness and yield unexpected benefits.

   *2.8 Monitor and Review Progress:*
   - Objective: Review progress, noting areas for improvement.
   - Reflection: "What’s working well? What could be improved?"
   - Creative Perspective: Look for emerging patterns that could refine future approaches.

   *2.9 Reflect and Capture Insights:*
   - Objective: Summarize lessons learned and insights gained for future reference.
   - Reflection: "What new understanding has emerged from this process?"
   - Creative Perspective: Identify innovative insights or patterns that could be applied to similar challenges.

3. *Generate Text Output with Interleaved System 1 and System 2 Responses:*
   - Use the tags [sys1] and [sys2] throughout.
   - Aim for a lengthier, detailed response. Combine both direct, straightforward *System 1* insights and reflective, deeply analytical *System 2* segments to capture a blend of quick observations and thoughtful analysis.

---

### *Example Input Text:*

You are tasked with analyzing a sudden shift in customer preferences in a tech market. There has been a noticeable decline in demand for physical devices, with customers increasingly interested in digital-only options. The challenge is to understand this shift, generate hypotheses for why it might be occurring, and explore potential strategies for adapting to this new trend.

---

### *Processed Output with System 1 and System 2 Thinking:*

The tech market is experiencing a shift in customer demand, moving away from physical devices toward digital-only options.

[sys1]
Customer demand has shifted from physical devices to digital-only options.
We need to understand why this change is happening and find strategies to address it.
Key factors may include cost, convenience, and technological trends.
[end sys1]

[sys2]
**2.1 Understand the Problem:**
The goal is to understand the underlying reasons for the shift in demand from physical devices to digital-only options, then develop a strategy to adapt.

*Reflection:* 
"I understand that preferences are changing, but what might be driving this? Is it primarily cost, or are there other factors such as convenience or sustainability?"

*Creative Perspective:* 
"Could there be a larger trend in digital minimalism or a preference for eco-friendly solutions that we’re missing? What unseen motivations might explain this shift?"

**2.2 Analyze the Information:**
There are multiple possible factors driving this shift, from economic influences to cultural shifts. It’s essential to isolate each factor and understand its impact.

*Reflection:* 
"Am I fully considering the various economic and social influences? Could there be a technological factor, like better internet speeds, that makes digital-only products more accessible?"

*Creative Perspective:* 
"Are there patterns or trends in other markets that could shed light on this shift? Could this be part of a larger trend toward virtual experiences?"

**2.3 Generate Hypotheses:**
1. Customers prefer digital options due to lower costs. (Confidence: 0.8, Creative: 0.4)
2. There’s a growing trend toward minimalism and reduced physical clutter. (Confidence: 0.7, Creative: 0.7)
3. Digital products offer greater flexibility and ease of use. (Confidence: 0.6, Creative: 0.6)
4. Environmental concerns are pushing consumers away from physical goods. (Confidence: 0.6, Creative: 0.8)
5. Advances in tech make digital-only options more functional. (Confidence: 0.8, Creative: 0.5)
6. Pandemic-era remote work increased demand for digital solutions. (Confidence: 0.7, Creative: 0.6)
7. Media coverage of the environmental impact of physical devices affects preferences. (Confidence: 0.5, Creative: 0.7)
8. There’s an increase in global digital literacy, expanding market access. (Confidence: 0.6, Creative: 0.6)
9. Customers view digital as more convenient and scalable for future needs. (Confidence: 0.7, Creative: 0.5)
10. Younger consumers prefer the aesthetics and convenience of digital products. (Confidence: 0.6, Creative: 0.6)

*Reflection:* 
"Have I considered all possible influences? Are there any surprising factors that could explain this shift?"

*Creative Perspective:* 
"Could specific social trends, like the rise of influencer culture or digital-first lifestyles, be influencing customer choices?"

**2.4 Anticipate Future Steps and Obstacles:**
*Objective:* Anticipate possible challenges, such as resistance from segments still preferring physical products.

*Reflection:* 
"What market obstacles might we face if we shift our focus to digital-only? Are there sub-segments that still prioritize physical products?"

*Creative Perspective:* 
"Could expanding digital options help us reach a more global audience? Are there emerging trends that we could leverage in our strategy?"

[end sys2]

[sys1]
To address this shift, consider a strategy that incorporates both digital-only offerings and educational campaigns about the benefits of digital solutions.
Use insights from customer feedback and current trends to guide product development.
Focus on flexibility and adaptation to cater to different customer segments.
[end sys1]


INTRODUCTION
============

Juvenile xanthogranuloma (JXG) is a proliferative histiocytic disorder of childhood and regarded as a non-Langerhans cell histiocytosis[@B7]. JXG is not a true neoplasm but rather a reactive proliferation of histiocytes and the etiology and pathogenesis are still unknown. The clinical features have been described as multiple, cutaneous and self-limited lesions occurring in children in their first 2 decades of life and, thus, have been called JXG[@B9],[@B14]-[@B17]. However, JXG occurring as extracutaneous lesion especially involving an isolated spinal column is extremely rare in an adult and the incidence has never been reported. Herein, the authors describe the unique case of a 29-year-old man harboring an isolated epidural C1 to C2 xanthogranuloma and treated with total surgical resection through partial laminectomy for the decompression of spinal canal and the maximal preservation of normal structures to maintain the cervical motion without instrumental fixation.

CASE REPORT
===========

A 29-year-old male patient presented with right side weakness and left side numbness that occurred just after a car accident. Upon physical examination, there was no abnormal finding, except for tenderness in the upper cervical area. Routine laboratory tests demonstrated normal results. Motor weakness of right side extremity was disclosed as 1/5 for arm and 2/5 for leg with slightly hyperactivity of deep tendon reflex. Sensory examination showed significantly decreased pain, temperature, vibration, and discriminatory touch sensations below the left C2 dermatome. Babinski\'s reflex and Hoffman\'s sign were present on the left side. Based on the symptoms and neurological findings, the assumptive diagnosis of Brown-Sequard syndrome was made. The patient had no symptoms or past medical history related to a cervical spine lesion before the trauma. Cervical plain films revealed straightening of the cervical spine with loss of normal lordosis and widening between the posterior arch of the atlas and spinous process of the axis. A computed tomography (CT) scan of the upper cervical spine revealed a large round mass which measured 25×18×24 mm with relatively homogeneous strong enhancement and was located between the C1 and C2 interspinous space. In addition, the CT scan showed cortical osseous erosions at the lower C1 posterior arc and upper C2 spinous process. Cervical magnetic resonance images (MRI) revealed an epidural dumbbell-shaped mass traversing the C1 to C2 interspinous space, compressing the surrounding structures ([Fig. 1](#F1){ref-type="fig"}). The spinal cord was compressed by the lesion which was isointense on T1-weighted image (WI) and mixed hypointense on T2WI with homogenous strong enhanced after gadolinium administration. Radiologic analysis indicated possible lymphoma, meningioma, schwannoma or other neuronal tumors.

The patient underwent a surgery immediately for decompression of the spinal cord. A total tumor resection was performed with only a partial laminectomy from the lower half of the C1 to upper half of C2 without any instrumentation and access to the tumor. After partial lamicectomy, an extradural and yellowish mass was exposed with well-demarcated from the surrounding structures but adhesive at the epidural area. Under microscopy, the tumor was delicately dissected, and en bloc removal was achieved ([Fig. 2](#F2){ref-type="fig"}). The mass was ovoid, soft like gelatin, avascular, and well-encapsulated, measuring 25 mm at the largest diameter, and was adherented to the outer layer of the dura mater. And, there was no root invasion. On the basis of the clinical and operative features, we thought that the lesion originated from the outer aspect of the dura mater. Upon sectioning, the mass was particularly yellow and white with cystic components ([Fig. 3](#F3){ref-type="fig"}).

After surgery, the patient\'s right hemiparesis fully recovered in 2 weeks. However, a slightly tingling numbness on his left arm remained and was controlled through medication in the outpatient clinic for 4 months. Currently, the patient has no symptoms without instability of cervical spine. Cervical MRI with gadolinium enhancement at 2 years after surgery demonstrated no recurrent lesion ([Fig. 4](#F4){ref-type="fig"}).

Histological examination of the tumor uncovered focal aggregation cells with ample, clear, and foamy cytoplasm in a background of loose, fibrous stroma of xanthic appearance. Large, round cells had irregular vesicular nuclei which were regular and small with condensed chromatin ([Fig. 4](#F4){ref-type="fig"}). The specimen was underwent to immunohistochemical testing, yielding strongly positive for CD 68 and lysozyme stain, which confirmed that the large foam cells were histiocytes. The test with CD-1a was negative, thus ruling out Langerhans\' cell histiocytosis. GFAP stain and S-100 protein were negative. Thus, a diagnosis of xanthogranuloma was established.

DISCUSSION
==========

In 1905, the first case of JXG was reported by Adamson[@B1], who termed the entity a congenital xanthoma multiplex, and is not a true tumor, but rather a reactive proliferation of histiocytes. JXG is the most common form of non-Langerhans cell histiocytosis. The actual incidence of JXG is unknown but may be higher than is generally recognized, because JXGs occur early in life. A male predominance has been noted in childhood; however, in adults, there is no sex predilection. Most tumors appear early in life with 5% to 17% of JXGs present at birth and 40% to 70% appearing during the first year of life. However, despite the term JXG, onset during adulthood is possible, with a peak incidence in the late 20\'s to early 30\'s[@B10]. Autopsy series suggest the incidence of these lesions varies between 1.6% and 7% of the general 2012population[@B3]. CNS involvement in cases of cutaneous and/or extracutaneous JXG is rare[@B8]. Isolated CNS JXG can be classified according to its localization and the site of implantation in the following : 1) cerebral intraparenchymal, 2) dural, and 3) origination from the cranial or spinal column[@B19]. Solitary xanthogranuloma, especially involving the spine, is exceedingly rare[@B4],[@B16],[@B18],[@B19].

To date, 12 such cases are found reported in the English literature[@B2],[@B5]-[@B7],[@B11]-[@B15],[@B19],[@B21]. Four of these were in the cervical spine, three cases involved the thoracic and five were lumbosacral lesions. There has been a single prior report of JXG involving the upper cervical spine (C2 nerve root in a 18-year-old female)[@B5]. To the best of our knowledge, the authors of the current study present the second report of a solitary JXG involving upper cervical spine. And this is the second report of a solitary xanthogranuloma occurring in a male adult (although the prevalence is without sex distinction). Almost all cases of intradural-extramedullary JXG were seen in infants because of the early symptom developing due to cord compression by the lesion[@B14],[@B19],[@B21]. Paravertebral JXG was founded in relatively elder age than ordinary JXG or in adults ([Table 1](#T1){ref-type="table"}). The authors considered naming the tumor \'solitary xanthogranuloma\', and excluding \'juvenile\' because the tumor was discovered in an adult. Analyzing the reported 12 cases involving the spine, the clinical features were related with the anatomic localization, as in slow-growing tumors, and gradually exaggerated except in the present case. Interestingly, the patient in the current study abruptly presented symptoms similar to Brown-Sequard syndrome after a car accident. The patient had no symptoms before, possibly because the tumor was located at the epidural space of the C1 to C2 level, without compression of the spinal cord. However, after trauma, an acute compressive myelopathy developed from the mass effect of the tumor.

A MRI is the best method for the localization of tumors and their relationship to adjacent structures. The lesion may appear hypo-, iso-, and slightly hyperintense in T1WI and T2WI. Schultz et al.[@B20] declared that spinal xanthogranuloma does not enhance, whereas cerebral xanthogranuloma does enhance homogenously with gadolinium. The tumor should be distinguished from other tumors of neural structure origin which arise from the nerve root ganglion or dura-mater (e.g. schwannoma, meningioma, neuroma, and lymphoma). Upon gross anatomic examination, the xanthogranuloma is a well-encapsulated and round lesion with a yellowish-to-grayish surface with or without cystic components. Xanthogranuloma is confirmed through pathological and immunohistochemical studies. Microscopically, there are foamy histiocytic cells with or without Touton giant cells, which can be found in a background of mononuclear cells, and spindle cells. In immunohistochemistry studies, xanthogranuloma has mononuclear cells, giant cells, and spindle cells which are positive for the lysozyme stain and CD68 but negative for CD1a and S-100 proteins, which are the reactive markers of Langerhans cells.

Currently, there is no standard treatment for solitary xanthogranuloma involving the CNS because of extremely low incidence. Moreover the tumors involving the spine may grow slowly without regression and make the symptoms gradually worsen. This characteristic is significantly distinct from the skin lesions which are spontaneous regression in natural course. Although there are only a few cases of spinal xanthogranuloma, as much as possible of the tumor should be removed, because the tumor is pathologically and clinically benign. Additionally, there is no report regarding a recurrent case of solitary CNS xanthogranuloma after gross total removal. Although there are some cases treated with chemotherapy or adjuvant therapy after partial resection, total resection with preservation of neural structures appears curative for patients. In the present case, the authors thought that, if possible, the tumor should be completely removed with preservation of normal structures and cervical motion. En bloc tumor resection was performed by minimal bone work, which included a partial hemilaminectomy at the lower half of the C1 and upper half of C2 without instrumentation or fixation. Finally, the patient\'s cervical motion could be preserved without instability and the symptoms relieved without complications. The patient should be followed for long-term and given medical observation after total resection, because the natural course of solitary CNS xanthogranuloma is unknown.

CONCLUSION
==========

The authors report the second case of a solitary CNS xanthogranuloma involving the spine in a male adult. Surgeons should consider differential diagnosis for such tumors in the spine. The tumor must be removed as much as possible with preservation of the neural structure, because of the curative potential for patients and the tumor\'s benignity. In addition, the patient should be followed up long-term and evaluated for the possibility of remission and recurrence of the tumor.

![Preoperative MRI showing abnormal signal intensities on epidural dumbbell-shaped mass (measuring 25×18×24 mm) traversing the C1 to C2 interspinous space, compressing surrounding structures. The dumbbell-shaped lesion reveals isointense on sagittal T1-WI (A), mixed hypointense on T2-WI (B), and well-enhanced after gadolinium administration (C). The spinal cord was compressed at the C2 level, and the signal change appeared on T2-WI. MRI : magnetic resonance images, WI : weighted image.](jkns-51-54-g001){#F1}

![Post-operative CT scan. Partial hemilaminectomy, from the lower half of the C1 posterior arch to upper half of C2 spinous process, was performed (A : mid-sagittal, B : 3-dimensional reconstruction). C : Follow-up MRI with enhancement after postoperative 2 years reveals no residual and no recurrence. CT : computed tomography, MRI : magnetic resonance images.](jkns-51-54-g002){#F2}

![Photomicrographs of the tumor reveals focal aggregation of cells with ample, clear, and foamy cytoplasm. There are large round cells with irregular vesicular nuclei. H&E, original magnification ×200.](jkns-51-54-g003){#F3}

![Gross finding of the tumor. A : External surface of the tumor; ovoid, yellowish, encapsulated with a white-colored adhesion scar at the mid-portion of the mass shown in the picture. B : Mid-section of the tumor, particularly yellow and white with cystic components.](jkns-51-54-g004){#F4}

###### 

Cases of solitary juvenile xanthogranuloma involving the spine reported in the literature

![](jkns-51-54-i001)

IDEM : intradural extramedullary, VB : vertebra body, CE : cauda equine, Homo : homogenous, NE : no enhancement, Ref. : reference, Gd : gadolinium, ↓ : low intensity, → : iso intensity, ↑ : high intensity, - : no comment, NM : not mentioned