Correct!
Answer 3. The FDG-PET findings are non-specific, and multiple differential diagnostic possibilities must be considered
Figure 3. 2-[18F]-Fluoro-2-Deoxy-D-Glucose positron emission computed tomography-CT fused images show increased tracer utilization in one of the larger nodules within the cystic lesion adjacent to the right cardiac border (arrow). The lingular nodule (arrowhead) shows little evidence of glucose utilization.
The FDG-PET findings are non-specific and could occur in the setting of malignancy, infection, or a number of proliferative lesions. The discrepant pulmonary nodular tracer uptake could suggest the possibility of two separate diagnoses, but the scan results are certainly not diagnostic of such).
The patient subsequently underwent percutaneous transthoracic lung biopsy of one of the nodules in the right lower lobe, and a diagnosis was obtained (figure 4).
Figure 4. Prone CT image obtained during percutaneous transthoracic lung biopsy shows the biopsy needle placed within a right lower lobe nodule
Diagnosis: Pulmonary amyloidosis with lambda light chains
Differential Diagnosis: The differential diagnosis of multiple nodules in the lung parenchyma is extensive, primarily including pulmonary malignancy and disseminated infections, in addition to numerous other considerations. The differential diagnosis of numerous cystic pulmonary lesions is somewhat narrower, and includes emphysema, bronchiectasis, Langerhans Cell histiocytosis, lymphangioleiomyomatosis, lymphocytic interstitial pneumonia (particularly in Sjögren syndrome), post-infectious pneumatoceles, follicular bronchiolitis, and Birt-Hogg-Dube syndrome. Rarely amyloidosis may present with a cystic appearance in the lung parenchyma. Occasionally pulmonary metastatic disease may present with numerous thin-walled cysts, particularly angiosarcomas. When a nodule-in-cyst appearance is present, metastatic disease, particularly cavitating squamous cell carcinoma, should be considered, but rarely pulmonary amyloidosis and benign metastasizing leiomyomas may manifest in this fashion as well. Nevertheless, even when the clinical history favors one particular consideration, tissue sampling is often required to establish the correct diagnosis when a nodule-within-cyst appearance is present.
References
1. Lantuejoul S, Moulai N, Quetant S, Brichon PY, Brambilla C, Brambilla E, Ferretti GR. Unusual cystic presentation of pulmonary nodular amyloidosis associated with MALT-type lymphoma. Eur Respir J 2007;30:589-592.
2. Sakai M, Yamaoka M, Kawaguchi M, Hizawa N, Sato Y. Multiple cystic pulmonary amyloidosis. Ann Thorac Surg 2011;92:e109.
3. Seaman DM, Meyer CA, Gilman MD, McCormack FX. Diffuse cystic lung disease at high-resolution CT. AJR Am J Roentgenol 2011;196:1305-1311.
4. Colombat M, Stern M, Groussard O, Droz D, Brauner M, Valeyre D, Mal H, Taillé C, Monnet I, Fournier M, Herson S, Danel C. Pulmonary cystic disorder related to light chain deposition disease. Am J Respir Crit Care Med 2006;173:777-780.