• Pleural nodules (when associated with pleural surfaces)
• Fissure-associated nodules

What is it? Fissural nodules are small, localized opacities occurring along or adjacent to the pleural fissures of the lungs. These nodules commonly represent lymphatic involvement, pleural-based processes, or conditions involving the visceral pleura.

Caused by:

• Commonly Caused by:
  • Sarcoidosis (often presenting with perilymphatic fissural nodules due to lymphatic involvement)
• Other Causes:
  • Benign:
    • Benign lymphatic hyperplasia
  • Infectious:
    • Tuberculosis (lymphatic spread or direct pleural involvement)
    • Fungal infections (e.g., aspergillosis, histoplasmosis)
  • Neoplastic:
    • Metastatic disease (e.g., breast, lung, ovarian cancer)
    • Primary lung cancer with lymphatic spread
  • Inflammatory:
    • Rheumatoid nodules
    • Cryptogenic organizing pneumonia (COP)

While lymphoid involvement is the most common cause, other etiologies can also lead to fissural nodules, such as:

• Direct pleural involvement: Seen in infections or metastatic cancers.
• Subpleural inflammation: Conditions like cryptogenic organizing pneumonia (COP) may mimic lymphoid involvement.

Resulting in:

• Nodular opacities along the fissures
• Localized pleural thickening along the pulmonary fissures
• Potential mass effect on adjacent lung structures

Structural Changes:

• Thickening of the fissure with nodular components
• Fibrosis and scarring in chronic cases

Pathophysiology:

• Nodular lesions along the fissures often result from lymphatic spread, direct pleural involvement, or inflammatory conditions causing nodular thickening.

Pathology:

• Benign: Fibrous tissue with granulomatous inflammation
• Malignant: Tumor cell clusters with desmoplastic reaction

Diagnosis:

• Clinical correlation with history of malignancy, autoimmune disease, or exposure to infections
• Radiologic assessment with CT and PET-CT
• Biopsy for tissue confirmation if malignancy is suspected

Clinical:

• Often asymptomatic
• May present with pleuritic chest pain, cough, or systemic symptoms in malignancy

Radiology:

CXR:

• Findings: Nodules along the fissures may present as thickened or irregular fissural margins
• Associated Findings: Pleural effusion or mass effect

Chest CT (preferred):

Parts: Discrete nodules seen along or within the pleural fissures.

Size: Typically small (<1 cm), but larger nodules may be present depending on the underlying cause.

Shape: Round or oval, occasionally irregular; may appear confluent in cases of lymphatic spread.

Position: Localized along the major or minor fissures of the lungs.

Character:

Calcifications may be seen in benign or treated lesions.

May exhibit contrast enhancement in malignancy or inflammation.

Other Relevant Imaging Modalities:

• PET-CT: Elevated SUV uptake suggests malignancy, while low SUV may indicate a benign process
• MRI: Rarely used, but can assist in characterizing pleural lesions

Pulmonary Function Tests (PFTs):

• Usually normal unless large lesions affect lung expansion

Management:

• Benign: Monitoring with serial imaging
• Malignant: Tissue sampling and oncologic treatment if indicated
• Infectious: Targeted antimicrobial therapy

Recommendations:

• Contrast-enhanced CT for detailed characterization
• Consider PET-CT for metabolic activity assessment
• Biopsy if the nodules remain suspicious

Key Points and Pearls:

• Fissural nodules are commonly associated with lymphatic spread due to the dense network of lymphatic vessels along the pleural fissures.

“Lymphatic involvement along the pleural surfaces, including the fissures, is a frequent finding in conditions like sarcoidosis and lymphangitic carcinomatosis.” Radiopaedia

• Sarcoidosis frequently involves perilymphatic regions, making fissural nodules a characteristic feature.

“Sarcoidosis prominently affects the perilymphatic regions, including the fissures, making it a diagnostic clue in imaging.” Radiopaedia

• Malignancies such as lymphangitic carcinomatosis often spread along the fissures.

“Lymphangitic spread of malignancies can involve the pulmonary fissures, resulting in nodular thickening and mass effect.” Radiopaedia

• Granulomatous Diseases like tuberculosis may present with fissural nodules due to lymphatic spread.

“Tuberculosis can involve the fissures through direct pleural involvement or lymphatic spread.” Radiopaedia

• Calcifications in fissural nodules often suggest a benign process such as prior granulomatous infection.

“Calcifications within fissural nodules are often indicative of prior granulomatous infection rather than malignancy.” Radiopaedia

This version now conforms to your latest TCV template requirements while maintaining a focus on the pulmonary fissures. Let me know if you need further refinements.