Clinical diagnosis
Case 276
【Progress】
Biopsy of subcutaneous was done and microscopic examination revealed sarcoidosis. She was scheduled to be given steroid therapy.
【Discussion】
Histologic specimen of sarcoidosis nodule reveals that it composes of phagocytic monocytes, macrophages, lymphocytes and epithelial cells forming noncaseating granuloma (1, 2). The etiology is yet to be known. However, immune response plays a key role to create sarcoidosis nodule. Especially, collaboration of macrophages and helper T (CD4) cells via interferon γ works intensively and makes immune cells accumulates, forming a nodule. What is yet to be clarified is what kind of simulation makes this collaboration. If virus or bacterial infection simulates this collaboration, antibody production from B cell or plasma cells for virus and neutrophils infiltration for bacteria should be found, respectively (1). In sarcoidosis, there was no proof of pathogen infection.
However, the similar response as sarcoidosis appeared in tuberculosis (Tbc), causing tuberculoma that indicates granuloma with accumulation of macrophages, helper T cells and B cells. The difference between tuberculoma and sarcoidosis is whether to from caseous necrosis in granuloma or not (3, 4, 5). Caseous necrosis implies bodies of macrophages after too much phagocytosis for Tbc bacilli. Non caseous necrosis indicates macrophages do not always die by phagocyting something.
Meanwhile, both tuberculoma and sarcoidosis form a nodule with making fibrosis. Fibrosis is considered to enclose something that macrophages can be unmanageable. Macrophages become to transform epithelioid cells and play a role to form fibrosis, namely create a nodule.
It is clinically crucial to differentiate sarcoidosis from malignant lymphoma or other malignant tumors such as small cell carcinoma. PET (positron emission tomography) using FDG (fluorodeoxyglucose), and MRI with DWI (diffusion weighted imaging) and ADC (apparent diffusion coefficient) were attempted for the differentiation. SUV (standard uptake value) is expressed in a formula: FDG accumulation radio-activity / volume of region of interest (ROI) / total FDG radio-activity / body weight. It indicates folds or degrees of FDG RI consumption of the ROI compared with RI body backgrounds. In other words, SUV implies a ratio of ROI (/cm3) consuming FDG compared to body (/cm3). However, there are reports that SUV was useless for the differentiation because SUV of sarcoid is as high as malignant lymphoma (6, 7).
Meanwhile, ADC implies diffusion degree of water molecules: The less ADC values indicates the more restriction of water molecule, in other words, less diffusion of water molecule, while the greater ADC values indicates less restriction of water molecule, in other words, greater diffusion of water molecule.
ADC values of fresh abscess, fresh hematoma, malignant tumor are in condition of less water molecule diffusion. Especially, ADC values of malignant lymphoma is around 0.5, adenocarcinoma 0.9 to 1.0, while ADC value of sarcoidosis is around 1.2 or greater (8, 9), indicative that ADC value is potential to differentiate from sarcoidosis from malignant lymphoma. ADC values of sarcoidosis are around 1.2, while those of malignant lymphoma are around 0.5, indicative of enabling to differentiate them.
【Summary】
We presented a seventy one-year-old female whose symptoms were cough, dyspnea and skin solid mass. Chest CT depicted multiple swollen lymph-nodes at bilateral hilum and mediastinum with peri-bronchial involvement and multiple subcutaneous mass. Microscopic examination of biopsy obtained from subcutaneous mass revealed sarcoidosis. It is borne in mind that it composes of phagocytic monocytes, macrophages, lymphocytes and epithelial cells forming noncaseating granuloma. Caseous necrosis implies bodies of macrophages after too much phagocytosis for Tbc bacilli. Non caseous necrosis indicates macrophages do not always die by phagocyting something. Collaboration of macrophages and helper T (CD4) cells via interferon γ works intensively and makes immune cells accumulates. Macrophages become to transform epithelioid cells and play a role to form fibrosis, namely create a nodule. PET-SUV was useless for the differentiation because SUV of sarcoid is as high as malignant lymphoma. Meanwhile, ADC values of sarcoidosis are around 1.2, while those of malignant lymphoma are around 0.5, indicative of enabling to differentiate them.
【References】
1.Saidha, et al. Etiology of sarcoidosis: does infection play a role? The Yale Journal of Biology and Medicine 2012; 85:133-41.
2.Newman, LS, et al. Sarcoidosis. N Engl J Med, 1997; 336:1224-1234
3. Sheffield EA. Pathology of sarcoidosis. Clin Chest Med, 18 (1997), pp. 741-754
4.Sinem N, et al. Abdominal sarcoidosis: cross-sectional imaging findings. Diagn Interv Radiol. 2015; 21: 111–117
5.Gregory M, et al. Sarcoidosis: A Diagnosis of Exclusion. American Journal of Roentgenology. 2020;214: 50-58.
6.Jerusalem G, et al. Positron emission tomography imaging for lymphoma. Curr Opin Oncol 2005; 17: 441-445
7.Shetty A, et al. Sarcoidosis mimicking lymphoma on FDG-PET imaging. 2011; 6 409
8.Lin C, et al. Whole-body diffusion-weighted magnetic resonance imaging with apparent diffusion coefficient mapping for staging patients with diffuse large B-cell lymphoma. Eur Radiol. 2010;20:2027–2038.
9.Santos FS, et al. MRI-based differentiation between lymphoma and sarcoidosis in mediastinal lymph nodes. J Bras Pneumol. 2021;47(2):e20200055.
2022.9.1