Objective:

To highlight the diagnostic challenges and misdiagnosis issues related to idiopathic multicentric Castleman disease, not otherwise specified (iMCD-NOS), through a detailed case study.

Approach:

• Case Presentation: A 53-year-old male presented with a 4-month history of persistent right submandibular lymphadenopathy and recurrent fever, leading to evaluations across multiple hospitals before a final diagnosis of iMCD-NOS.
• Diagnostic Strategy: The case emphasizes the importance of excisional biopsy over core needle biopsy and the systematic exclusion of differential diagnoses, including HHV-8 infection.

Key Findings:

• The patient presented with persistent lymphadenopathy, recurrent fever, and elevated inflammatory markers, including leukocytosis and eosinophilia.
• Histopathological examination revealed disrupted lymph node architecture with both atrophic and hyperplastic follicles, and immunohistochemistry demonstrated positivity for CD38, CD138, IgG4, and IgG.
• Final diagnosis of iMCD-NOS was made after excluding HHV-8 infection and other mimickers, highlighting the complexity of the diagnostic process.

Interpretation:

The case illustrates the complexity of diagnosing iMCD-NOS and the necessity for thorough diagnostic procedures.

Limitations:

• The rarity of iMCD-NOS may limit the generalizability of findings to broader patient populations.
• This case study reflects a single patient's experience, which may not encompass all presentations of the disease.

Conclusion:

The case underscores the importance of thorough diagnostic procedures in recognizing iMCD-NOS to reduce diagnostic delays.