Inverted Papilloma: Diagnosis and Modalities

• Inverted papilloma (IP) is a benign but locally aggressive sinonasal tumor, arising from the Schneiderian epithelium

Diagnostic Modalities for Inverted Papilloma

• Diagnosis relies on a combination of clinical findings, endoscopic examination, and radiological imaging, with histopathological confirmation

Clinical Evaluation

• Nasal obstruction and epistaxis are common presenting symptoms
• Other symptoms include facial pain, headache, anosmia, and/or secondary infection

Endoscopic Examination

• Nasal endoscopy allows direct visualization of the nasal cavity and paranasal sinuses.
• IPs typically appear as polypoid masses, often originating from the lateral nasal wall, particularly the middle meatus or ethmoid sinuses
• Endoscopy helps in assessing the extent of the tumor and identifying its site of origin
• Inverted papillomas may have a characteristic cerebriform appearance

Radiological Imaging

• Imaging is crucial for determining the tumor's extent, assessing bony erosion, and planning surgical approach.
• CT scans and MRI are the primary imaging modalities.

Computed Tomography (CT) Scan

• CT scans provide detailed bony anatomy, helping to identify bony erosion or remodeling, a common feature of IPs
• On CT, IPs typically appear as soft tissue masses with a characteristic cerebriform (brain-like) pattern
• CT is also useful for identifying areas of hyperostosis (thickening of the bone) associated with the tumor
• Opacification of the sinuses due to the tumor and any associated inflammation can be evaluated
• CT is useful in surgical planning to define the relationship of the tumor with adjacent structures such as the orbit or skull base

Magnetic Resonance Imaging (MRI)

• MRI provides better soft tissue detail than CT scans
• MRI helps in differentiating the tumor from retained secretions or inflammatory changes
• Inverted papillomas typically exhibit intermediate signal intensity on T1-weighted images and high signal intensity on T2-weighted images
• MRI is valuable for assessing intracranial or orbital extension of the tumor
• The "cerebriform pattern" can also be appreciated on MRI
• MRI can help in detecting early signs of malignancy or synchronous malignancy

Histopathological Examination

• Histopathological examination of tissue samples obtained via biopsy is essential for confirming the diagnosis of inverted papilloma
• The hallmark of IP is the inversion of the epithelium into the underlying stroma
• The epithelium is typically squamous or columnar, with varying degrees of dysplasia
• Microscopic features include:
  • Inward growth of the epithelium
  • Lack of a distinct basement membrane
  • Presence of microcysts and mucous-filled glands within the epithelium
  • Variable amounts of inflammatory cells in the stroma
• Grading can be performed in IP to assess for dysplasia

Differential Diagnosis

• Several other sinonasal conditions can mimic inverted papilloma:
  • Nasal polyps: Usually bilateral and associated with allergic rhinitis or chronic sinusitis.
  • Fungal infections: Can present as masses in the sinuses, often with characteristic imaging findings.
  • Sinonasal malignancies: Such as squamous cell carcinoma or adenocarcinoma, which can be distinguished by histopathology and aggressive growth patterns.

Diagnostic Algorithm

• A typical diagnostic approach involves:
  • Clinical history and physical examination
  • Nasal endoscopy to visualize the tumor
  • Radiological imaging (CT and/or MRI) to assess the extent of the tumor
  • Biopsy for histopathological confirmation