Brief Answer:
Follow up CT scan to be done after 6 months is recommended internationally

Detailed Answer:
Hi XXXX,
Thanks for writing in to us.

I have read through your query in detail.
Please find my observations below

1. The nodules are small and not exactly a concern if it measures 3 to 5 mm. As per internationally followed Fleischner guidelines, the Recommendations for Follow-up and Management of Nodules Smaller than 8 mm Detected Incidentally at CT are as follows.
(i) A nodule 4 to 6 mm in a low risk patient (non smoker and no other risk) requires imaging follow up at 12 month
(ii) A nodule 4 to 6 mm in a high risk patient (smoker) to be followed up by doing another CT at at 6-12 months and then at 18-24 months if no change

2. When assessing likelihood of malignancy for a nodule, the following criteria are evaluated
(i) Age: The risk of malignancy in a lung nodule is 15% between ages 40 and 49
(ii) History, underlying risk factors: Smoking, asbestos exposure, previously diagnosed malignancy and fever are risk factors
(iii) Size of lesion: 80% of benign nodules are less than 2 cm, but 15% of malignant nodules are less than 1 cm
(iv) Border characteristics: Benign lesions tend to be smooth and discrete. Malignant lesions have irregular, lobulated or spiculated borders. However 21% malignant nodules have well defined margins.
(v) Calcification of lesion: Eccentric or Amorphous calcification indicates malignancy usually
(vi) Cavitation of lesion: This may or may not be present with thick walls in malignancy and is not a sole criteria.
(vii) Presence of fat in lesion: Fat is an indicator of a possible benign tumor
(viii) Growth rate of lesion: Malignant lesions have roughly a doubling time between approximately a month and a year. This is difficult to measure in a small nodule. For example a nodule measuring 4 mm (volume 33.51 cu mm) can double in volume to become 5 mm (volume 65.45 cu mm) and another one measuring 3.0 cm (volume 14.14 cc) will double in volume to become 3.75 cm (volume 27.61 cc). Therefore the growth rate both are the same during a similar duration but to the eye the appearance might differ. This needs to be accurately measured and hence the guidelines suggest 6 month period for the high risk group after which another CT scan is to be repeated.

3. As your husband has a history of RCC 2 years back therefore it is important to closely follow up the nodules and make sure they are not a part of malignant process by doing repeat CT scan at 6 months and following international guidelines.

Hope this answers your question. Please feel free to correct any oversight in my interpretation of your problems and discuss them in detail as per your requirements.

Hope your query is answered.
Do write back if you have any doubts.

Regards,
Dr.Vivek

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