Hi. Sorry to hear about the complaints of your mother in law. So far as your question is concerned, keeping in view her age , any mass anywhere in the body should taken seriously and investigated thoroughly to rule out any serious illnes or to manage at an earlier stage of illness. You have not given the description of the mass and location of the mass, so its almost impossible with the info provided to reach to a conclusive diagnosis.
After history and physical examination, tests that may help in making a diagnosis may include xrays,
ultrasonography,
ct scan ,
MRI , transvaginal ultrasonography, contrast studies and laproscopic procedures and tissue
biopsy. The choice of test depends upon the organ/system involved.
For example for
urinary system investigations needed may include urine examination, blood examination, ultrasonography, xray KUB, CT Scan, MRI, Cystocopy, micturating cystourethrogram and tissue biopsy.
For genital tract, tests may include ultrasonography, CT scan, MRI,
hysterosalpingography, transvaginal sonography, harmonal studies, laproscopy and tissue biopsy.
Similarly for GIT , investigations may include XRAYs, Ultrasonography, Ct scan , MRI, stool examination, laproscopy and tissue biopsy etc.
Hope these line may help you make a better understanding of the requirements of your mother-in-law.
Wishing you and your loved ones the best of health.
Regards.