Metastasis VS. Bacterial Infection/Septic Emboli

After small nodules showed up on a CXR, my mother had a CT scan performed.  The Impression lists:  Multiple pulmonary nodules seen in both hemithoraces concerning for metastatic disease to the chest and lungs but also gives a Differential diagnosis that states consideration could include an atypical bacterial infection with septic emboli.  I have some medical knowledge, but am unsure what may come next for her i.e lung biopsy, etc...  Is it common for pulmonary nodules to be bacterial infections.  Is a differential diagnosis always given as an alternative?
If this is metastatic disease to the chest and lungs, wouldn't that mean that there is a primary that has yet to be discovered?

[Monica M, MD]

Hi,

Various differential diagnoses are considered for multiple pulmonary nodules. These include infections, inflammatory conditions such as granulomas, metastasis etc. An FNAC or a biopsy from the lesions is needed to confirm the diagnosis. If metastasis is confirmed on FNAC/Biopsy, the primary tumor may be in the lung or elsewhere and additional investigations may be indicated to discover the primary tumor.
All the best!

[CThomas242]

The doctor has set her up for a PET scan and said depending on the numbers, he would see how to proceed.  He said he has an idea of the diagnosis but will not say until PET scan results are in.  What does a PET scan tell you?

[Monica M, MD]

Hi,
PET scan detects metabolically active areas in the body. It detects the uptake of a tracer labeled with a radionuclide. In many conditions such as infections, inflammations, cancers etc. the affected cells are metabolically more active than normal cells and therefore show increased uptake of the tracer. The intensity of uptake may vary depending on the condition ie it may be more in cancer cells than in inflammations. The uptake is quantified using a parameter called "Standardised uptake value (SUV)" which is a number that depicts the degree of tracer uptake. The SUV may indicate whether the lesion is benign or cancerous. However, the diagnosis needs to be confirmed with an FNAC/biopsy.
All the best!