Developmental disorders of the thyroid gland are very rarely described in the literature. So far publications in the Czechoslovak and Czech otolaryngological literature summa- rize these less common findings of therotopic tissue in nine patients (9, 11, 13, 15, 16, 19, 20, 23, 27). Therapeutic procedures in heterotopic tissues are described only very rarely (4, 5). In the world literature more than 650 cases of impaired descensus of the thyroid are described. The classification and nomenclature of these heterotopic tissues are done without clinical classification. When thyroid tissue is found beyond the normal physiological site it is always necessary to rule out a secondary of a malignant thyroid tumour. To rule out secondaries of a differentiated carcinoma it is necessary to consult a pathologist, in particular when thyroid tissue laterally from the median line is involved. In the differential diagnosis of tissue it is important to differentiate tumourous disease of another origin (cysts, carcinoms, myoma, fibroma, lymphosarcoma, lymphangioma, angioma, amyloidosis, hyperplasia of lymphatic tissue, gumma, lymphoma). In case of aberrant thyroid tissue it is essential to rule out unequivocally differentiated thyroid carcinoma. The finding of aberrant thyroid tissue is extremely rare and it can therefore be easily mistaken for a secondary of well differentiated thyroid carcinoma. The authors describe eight cases of heterotopic thyroid tissue. They discuss different approaches to treatment of this anomaly and describe the systematic classification of developmental experience with treatment and follow-up of patients with heterotopia of thyroid tissue. Based on the described experience they suggest a modified approach to the treatment of heterotopic thyroid tissue: A) Medicamentous therapy This approach is recommended in particular in child patients. Treatment is supervised by an endocrinologist who indicates suppressive substitution treatment by synthetic hormonal preparations. The patients must be checked after short intervals in an endocrinological department. In child patients the team must comprise a paediatrician. After completed development the patients are treated as in group B. B) Surgical treatment This treatment involves complete removal of the thyroid gland. This must be followed by endocrinological treatment and full substitution treatment. These patients must be followed up in an endocrinological and ENT department.

        Key words: heterotopia of the thyroid gland, classification of heterotopia, treatment of heterotopic tissue.