Granulomatous Diseases

and Robert W. Henderson¹

(1)

Department of Radiology, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA

Case 16.1: Sarcoidosis

History

50-year-old male, with history of esophageal cancer, status post esophagectomy with gastric pull-through.

Findings

Symmetrically intense FDG activity seen within bihilar and mediastinal lymph nodes, demonstrating hypermetabolism of similar intensity (Figs. 16.1 and 16.2).

Fig. 16.1

Fig. 16.2

Impression

Findings compatible with sarcoidosis by scan pattern (which was proven on surgery, during esophagectomy and gastric pull-up).

Pearls and Pitfalls

The hypermetabolic lymph nodes could have been mistaken for metastatic disease.

Discussion

Etiology for granulomatous disease (noncaseating) is unknown.

Characteristic scan pattern: nodal disease involving mediastinal (lower paratracheal, aortopulmonary window, subcarinal), bilateral hilar, and interlobar lymph nodes.

Parenchymal disease is a late feature; by then nodal disease may have regressed.

¹⁸FDG-PET scan pattern is similar to ⁶⁷Ga scan (lambda pattern) in the region of the chest.

Symmetric FDG avid bihilar lymphadenopathy would be a rare pattern for metastatic disease (Figs. 16.1 and 16.2).

Case 16.2: Pneumoconiosis

History

55-year-old male, sand blaster by occupation, presents with chronic cough.

Findings

Lambda pattern of lymphadenopathy involving mediastinal and bihilar nodal regions (Fig. 16.3, yellow arrow). Particles predominantly seen in the upper lobes of the lung, as shown here in the right upper lobe image (Fig. 16.4, red arrow).

Fig. 16.3

Fig. 16.4

Impression

Silicosis based on correlation with patient’s occupational exposure history, presence of hypermetabolic mediastinal and bihilar lymph nodes (lambda pattern), and visualization of multiple small pulmonary nodules, predominantly in the upper lobes.

Discussion

Involvement of upper lobes predominantly. This is related to lymphatic drainage, which is better in the lower chest, as it is assisted by more excursion.
Particles that pass the respiratory bronchioles into the alveoli are drained by lymphatics, due to lack of cilia.
Exception, being asbestosis (whose needles are not cleared by lymphatics) (Figs. 16.3 and 16.4).

Case 16.3: Asbestosis

History

55-year-old male with asbestosis.

Findings

Fibrotic changes in the lower lung fields demonstrating low-grade FDG activity on PET and PET/CT fused images (Fig. 16.5). Pleural plaque in the left lower lobe (red arrow).

Fig. 16.5

Impression

Sequela to prior asbestosis exposure.

Discussion

Differentiating idiopathic pulmonary fibrosis from asbestosis is important because of legal and compensatory issues (Fig. 16.5).

Case 16.4: Prior Tuberculosis /Old Granulomatous Disease

History

Patient with known history of prior tuberculosis (TB).

Findings

Symmetric bihilar nodal activity within normal-sized lymph nodes (Fig. 16.6).

Fig. 16.6

Impression

Granulomatous disease by scan pattern.

Pearls and Pitfalls

Granulomatous disease (GD) is by far the commonest false-positive finding for nodal disease in the chest. In majority of the time, the hilar and med iastinal lymph nodes cannot be readily biopsied. Therefore, the classic scan pattern for GD must be identified on PET/CT.

Discussion

Active nodes common.
Does not imply active infection or need for treatment.
May or may not be associated with calcifications.
Nodes usually are normal size.
Usually bilateral (Fig. 16.6).

Case 16.5: Granulomatous Disease in the Midst of Hodgkin’s Lymphoma

History

56-year-old male, with history of Hodgkin’s disease (HD) below the diaphragm and prior history of tuberculosis. PET/CT images during chemotherapy (Fig. 16.7, top images); post chemotherapy PET/CT (Fig. 16.7, bottom images).