Editing Lung nodules (section)

== Imaging ==

* Risk factors for cancer
** Nodule diameter
** Spiculation/irregular/lobulated
** Upper lobe location
** Growth rate
** Calcification pattern
*** Benign = diffuse, central, laminated
*** Popcorn pattern = hamartoma
****
*** Indeterminate = punctate, eccentric, or amorphous
** Contrast enhancement (>20HU is likely malignant, <15HU is likely benign)
** Metabolic activity on PET
** Air bronchograms and pseudocavitation - often malignant
***
* Other factors
** Fat-containing nodules are virtually always benign (hamartomas) - malignancies could theoretically be lipomas or RCC mets but very rare
** Benign features - well-defined, smooth, round
** Pulmonary lymph nodes - small, solid, polygonal, perifissural, oval, pleural/septal/vessel attachment
** Halo and reverse halo signs are non-specific and can be seen in both benign and malignant lesions
* Classification
** Solid
** Subsolid
*** Subtypes
**** Pure ground-glass nodules
**** Part-solid/mixed nodules
*** Many subsolid nodules are inflammatory
*** Persistent ground-glass lesions carry a high risk of neoplasm
*** Mixed nodules are highest risk, with a higher solid component meaning higher risk of invasive cancer
**
* CT without contrast, thin slice
** 8-51% of CT shows a lung nodule
** Features
*** Size
*** Attenuation
*** Growth or stable size
**** Growing nodules (>2mm) should be examined pathologically
*** Calcification and fat
* PET
** Best way to evaluate metabolism of indeterminate nodules
** Solid nodules measuring >8mm that are not FDG avid are likely to be benign
** SUV >2.5 is typically used to detect lesions with a high probability of malignancy
** Not as good for subsolid nodules - be aware that slow-growing tumours (adenocarcinomas, carcinoids, low-grade lymphomas, metastases from renal cell carcinoma and mucinous neoplasms) can show little glucose uptake
** Inflammatory lesions are difficult to differentiate from malignant processes on PET