Sarcoidosis is a systemic disease, but mediastinal and pulmonary involvement is the most common manifestation in over 90% of cases [1]. Although the Scadding classification, established in 1961, remains widely used, nowadays high-resolution computed tomography (HRCT) has become a routine tool in diagnosing and evaluating lung sarcoidosis [2]. HRCT provides far more detailed information than a chest X-ray, prompting the need for a new classification system to define novel and distinct forms of the disease.

Numerous case reports in the literature describe specific forms of pulmonary involvement in sarcoidosis, highlighting both "typical" and "atypical" features. However, they may, in fact, represent more frequent or less common presentations of the disease. A phenotype-based approach is discussed in the Delphi study by Desai SR et al. [3], which led to a new HRCT classification of sarcoidosis based on expert consensus. The study identified four non-fibrotic phenotypes and three fibrotic phenotypes, suggesting that certain phenotypes might show specific impairments in pulmonary function tests or a poorer response to treatment, which could indicate a higher severity of the disease. These findings may provide the foundation for a new classification system for sarcoidosis based on HRCT, which is recommended as a baseline investigation.

To further explore this, we retrospectively evaluated CT exams of over 100 patients diagnosed with sarcoidosis, selecting representative cases for different phenotypes.