13year old DSH, presents with a 2-3 month history of coughing, increased respiratory effort and a large palpable throat mass. Aspiration yielded 80 ml of blood tinged fluid. T4 is increased ( 84 nmol/l), consistent with mild hyperthyroidism.

Increased T4 , increased ALP and ALT. Cytology of the fluid reveals a moderate mixed picture with neutrophils, many macrophages, frequent degenerate crystals and occasional clusters of the atypical epithelial cells shown here. Some of these cells contain very large nuclei (macronuclei) and others contain uneven numbers of nuclei. Occasionally the cytoplasm of these cells contains dark granules with similar granules present in macrophages.

The appearance of the cells strongly suggests a malignant epithelial neoplasm and the dark granules are a characteristic feature of thyroid tumours. Cytological diagnosis is cyst formation associated with a thyroid adenocarcinoma.