The current definition of papillary microcarcinoma is a papillary thyroid histology
According to existing WHO classification - yes, papillary microcarcinoma - is papillary carcinoma less than 10 mm in diameter.
In clinical practise IHC is often used when a suspicion to thyroid tumor methastasis is observed and there is no primary localisation of the tumor identified. In such cases even IHC to Thyroglobulin (Tg) may help. Unfortunately, there are no "special" IHC markers for this tumor. There are some special featurues of IHC expression, which may help to distinguish benign from malignant neoplasms (such markers as CK19, HBME1, TTF1, p53, Galectin-3, NIS, etc.), but they are not "specific". In routine diagnostics papillary microcarcinoma is usually based on histological criterias: complex, branching, randomly oriented papillae with fibrovascular cores associated with follicles, lined by cuboidal cells, nuclei are overlapping with finely dispersed optically clear chromatin (also called ground-glass, Orphan-Annie nuclei, not seen in cytology or frozen section material), micronucleoli, eosinophilic intranuclear inclusions (represent cytoplasmic invaginations) and nuclear longitudinal grooves (represent folding of redundant nuclear membrane, but nonspecific), psammoma bodies.
Hello
Good morning,
Young Pathologists
I think this is very good question which asked by Dr. Michael Pakdaman.
In my opinion
1-5 mm diameter = papillary tumor of thyroid (without any invasion)
6-10 mm = micropapillary carcinoma of thyroid (without any invasion or any other focus)
They have classical microscopic features of the papillary carcinoma of the thyroid.
International Classification of Disease for Oncology / ICD-O number is blowe
8341/3 Papillary microcarcinoma (C73.9)
Nickolay Fedchenko 's explanation is very good about histopathological and IHC findings too.
Good luck everybody. M. Şerefettin Canda
As far as I know, the definition of papillary microcarcinoma was first coined due to its excellent prognosis than that of the tumors with larger sizes. However, its clinical significance is becoming limited because many papillary microcarcinoma also accompany with frequent lymph node metastasis regardless of the tumor size and many tumors with larger sizes also does not show very bad prognosis. And even some scientists are now insisting to call them as papillary tumor not as carcinoma because they show excellent prognosis as Dr. Canda mentioned.
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