Autoimmune thyroiditis (AI) and differentiated thyroid cancer as papillary type (PTC) are sometimes associated and several common pathogenic mechanisms have been described: BRAF mutations, hOGG1 loss of heterozygosity, interleukin-10 activation, selenoproteomas disturbances. Controversies are related to a more aggressive profile of PTC if AI is presented by interferences with oxidative stress and secondary carcinogenesis. This is a case report of a 37-year old female diagnosed a decade ago with multi-nodular goiter and hypothyroidism. She was treated in different endocrine centers. She started to accuse intermittent breathing difficulties which were not related to her previous diagnosis of asthma. On admission, the thyroid function was normal under levothyroxine (LT4) therapy with high anti-thyreoperoxidase antibodies levels of 1000 UI/mL (Normal<35) confirming AI. Thyroid ultrasound showed multiple nodules of 10 millimetres (mm), and a dominant one on the right lobe of 20 mm. Total thyroidectomy and lymph nodes dissection was performed. Pathological report confirmed AI and micro-PTC was identified (of 3 by 2 mm; T1N0M0). The thyroid scintigrame was negative when LT4 substitution was stopped and the blood thyroglobuline (TG) was very low (of 0.2 ng/mL) with negative anti-TG antibodies. A good outcome is estimated and no radioiodine ablative therapy was added only TSH suppressive doses of LT4. This case confirms that long standing autoimmune hypothyroidism might not protect of differentiated thyroid cancer but the papillary microcarcinoma display a good prognosis, in this particular situation based on small dimensions of the lesion and low levels of TG after surgery.