Spontaneous thyroid follicular adenoma in a laboratory mouse (Mus musculus)

Spontaneous thyroid micro-follicular adenoma was found in an 18-month-old nursing Swiss albino mouse. The lesion was first noted as a tiny bulge at the base of the neck. The tumor was solid, and within two months, had grown such an enormous size that movement, feeding and suckling of the litter were greatly hampered. The litter of seven mice later died due to improper nursing while their mother remained generally unaffected by the mass.