Zmiany pęcherzykowe cytologicznie podejrzane

Diagnostyczne cechy cytologiczne

  • rozmaz bogatokomórkowy
  • dominuj?ce uk?ady drobnop?cherzykowe lub beleczkowe
  • st?oczone i nak?adaj?ce si? komórki
  • zmiany komórkowe (ma?a atypia, jednolite powi?kszenie)
  • sk?py koloid lub jego brak

Kilka z tych cech powinno by? obecnych, aby  rozpozna? zmian? „cytologicznie podejrzan?”. Znaczna atypia j?drowa i mitozy zazwyczaj nie wyst?puj?. Makrofagi s? nieobecne. Nagie j?dra s? zwykle pojedyncze lub nieobecne.

Nie ma jednego kryterium, które by?oby wystarczaj?ce do odró?nienia guzka ?agodnego od podejrzanego. Obecno?? kilku cech  zwi?ksza prawdopodobie?stwo z?o?liwo?ci i w takim przypadku powinno si? postawi? rozpoznanie guzka p?cherzykowego podejrzanego.  Rozmazy, które zawieraj? wy??cznie populacj? komórek Hurthle’a s? z definicji podejrzane.

Diagnostyka ró?nicowa obejmuje inne nowotwory tarczycy. Szczeliny j?drowe i pseudowodniczki mog? by? ogniskowo obecne w niektórych gruczolakach i rakach p?cherzykowych.  Je?eli maj? charakter ogniskowy, nie powinno si? rozpoznawa? raka brodawkowatego, ale zmian? powinno si? okre?li? jako podejrzan?. W tzw. szkliwiej?cym gruczolaku beleczkowym w rozmazie wyst?puj? komórki owalne lub wrzecionowate,  w skupiskach lub w rozproszeniu. Kluczem do rozpoznania tego guzka s? spiralne i  równoleg?e szeregowe uk?ady komórek, bezpostaciowy, szklisty materia? i oko?oj?derkowa strefa przeja?nienia. Wariant jasnokomórkowy raka p?cherzykowego mo?e by? pomylony z guzami przytarczyc lub przerzutem raka jasnokomórkowego nerki, ale komórki  zazwyczaj wykazuj? immunohistochemicznie dodatni odczyn na obecno?? tyreoglobuliny.  

Jedynie oko?o 30 – 40% przypadków ocenionych jako podejrzane okazuje si? guzami z?o?liwymi. W?ród nich, jedynie 50 – 75% stanowi? raki p?cherzykowe, pozosta?e za? s? wariantem p?cherzykowym raka brodawkowatego.

Klasyfikacj? Thy wymy?lono na potrzeby kliniczne, aby odseparowa? zmiany o wysokim ryzyku z?o?liwo?ci od zmian o ma?ym ryzyku. W obu przypadkach chirurg zaproponuje wyci?cie guzka, ale w pierwszym przypadku (kategoria Thy4) ryzyko wynosi oko?o 80%, za? w drugim (Thy3) – oko?o 20%. U pacjentów z rozpoznaniem „guzek p?cherzykowy podejrzany” zazwyczaj wykonuje si? lobektomi?; je?eli w badaniu histologicznym zostanie rozpoznany rak, zaleca si? ca?kowite wyci?cie tarczycy.

Próbuje si? wykorzysta? dodatkowe techniki do odró?nienia zmian p?cherzykowych ?agodnych od podejrzanych. Morfologia i analiza obrazu nie jest wystarczaj?co dok?adna z klinicznego punktu widzenia. Pomiary DNA w cytometrii przep?ywowej  nie s? równie? u?yteczne; aneuploidia nie gwarantuje, ?e guz jest z?o?liwy. Badanie immunohistochemiczne z MIB-1 nie ma wi?kszej warto?ci, gdy? aktywno?? proliferacyjna w gruczolakach i rakach mo?e by? podobna. Ocena immunocytochemiczna galectin-3 wydaje si? obiecuj?ca, poniewa? w wi?kszo?ci raków odczyn jest dodatni, a w wi?kszo?ci gruczolaków ujemny, ale  metoda nie jest specyficzna ani wystarczaj?co czu?a z punktu widzenia praktyki klinicznej. Do diagnostyki ró?nicowej mo?na wykorzysta? te? zmiany genetyczne: translokacja t(2;3) jest specyficznym markerem dla raka p?cherzykowego.

Nuclei showing a coarse chromatin pattern and nuclear grooving. A follicular lesion with nuclei showing a coarser chromatin pattern and nuvlear grooving.
The same lesion confirming a coarsely granular chromatin, mild nuclear pleomorphism. A high power view showing a coarsely granular chromatin and mild nuclear pleomorphism. Although there is some nuclear overlapping this feature is not so reliable in thicker clusters of cells.
Cells exhibiting some crowding, mild pleomorphism and irregular chromatin -  An MGG stain showing a microfollicular pattern with cells exhibiting some crowding, mild pleomorphism and a more irregularly granular chromatin.
Changes can be very focal and admixed with otherwise unremakable areas. This a rather bland follicle; in suspicous follicular lesions changes can be very focal and admixed with otherwise unremakable areas.
A rather crowded group of thyrocytes showing mild pleomorphism. A rather crowded group of thyrocytes showing mild pleomorphism; although a follicular arrangement can be identified nuclei are overlapping thoughout the group. This does not appear to be dictated by thickness of the cluster but is rather an expression of a more disordered architecture.
A nuclear pseudoinclusion in one cells and a flake of dense colloid. A monolayered sheet of thyroid cells which appear uniform, however a nuclear pseudoinclusion is visible in one cell and a flake of dense colloid is present at the upper right corner of the field (MGG); these would qualify the lesion as suspicious. Elsewhere more obvious features of papillary carcinoma, follicular variant were present.
A crowded group with prominent nucleoli and obvious nuclear grooves. A group of overlapping thyroid cells with prominent nucleoli and obvious nuclear grooves (Pap) in a blood stained smear. These features are suspicious but quantitatively insufficient for a definitive diagnosis of malignancy: other findings must be present.
Two similar groups of thryoid cells with prominent nucleolus and mild nuclear pleomorphism. Two groups of thryoid cells with prominent nucleolus and mild nuclear pleomorphism.
Nuclear overlapping in the upper left corner of the fragment. This lower power view of a Papanicolaou stained microbiopsy still identifies sheets of monolayered uniform thyroid cells which elsewhere showed suspicious nuclear features. You may note the more disordered architecture with nuclear overlapping in the upper left corner of the fragment. This low power finding should prompt an accurate screening of the slides for confirmation of suspicious features, this architectural feature alone being insufficient for diagnosis of suspicion.
A group of cells with marked anisonucleosis. A high power view of an MGG stained smear showing a group of cells with marked anisonucleosis, again a finding which should prompt a thorough search for more diagnostic features of suspicion for malignancy.
A central nucleus is much larger, hyperchromatic and has an irregular contour. A group of thyrocytes: a central nucleus is much larger, hyperchromatic and has an irregular contour (MGG). This is a suspicious finding.

Follicular carcinoma

It represents the second most common thyroid cancer (5-15% of thyroid malignancies). It is usually a solitary nodule but, differently from follicular adenoma, it shows capsular infiltration and vascular invasion. Follicular carcinoma is usually divided into two histological subtypes: a minimally invasive with a very good prognosis and a widely invasive with poor prognosis, which tends to metastatize to lung and bones.

The cells of follicular carcinoma never show the nuclear features of papillary carcinoma, which helps to distinguish follicular carcinoma from the follicular variant of papillary carcinoma.

An MGG stain of an FNA from a follicular carcinoma. This case was mistakenly thought to be a medullary carcinoma because of the presence of cytoplasmic granules; it proved to be a follicular carcinoma. The granules are not the fine metachromatic ones found in medullary carcinoma and probably represent lysosomes. In our experience the vast majority of follicular carcinomas are labelled as suspicious follicular lesions.
Groups of thyrocytes from a follicular carcinoma.

 

Hürthle cell tumours

Hürthle cells (oncocytes) are altered follicular cells which are very rich in mitochondria. In cytologic smears, they appear as polygonal cells, with large and finely granular cytoplasm, purple with MGG staining and orangeophilic with Papanicolaou staining. They can be binucleated, nuclei are enlarged and their size may be variable, often with prominent nucleoli.

Hürthle cells are common in Hashimoto`s thyroiditis and in multinodular goiter, where they can also form macroscopic nodules. Benign Hürthle cells are usually cohesive and do not have prominent nucleoli; a slight or moderate pleomorphism can sometimes be observed. In Hashimoto`s thyroiditis, they are admixed with numerous lymphoid cells. In nodular goiter, they are admixed with macrophages and colloid.

In Hürthle cell tumors the aspirate is generally composed of a pure Hürthle cell population. The cells are usually discohesive, but aggregates can be seen. Vesicular nuclei and prominent nucleoli are often present. In the case of a Hürthle cell neoplasm, normal follicular cells are usually absent and so are abundant lymphocytes; colloid may be present.

The differential diagnosis includes some variants of papillary carcinoma, such as tall/pink cell and oncocytic. Moreover, rare Hürthle cell tumors show papillary architecture (oncocytic papillary neoplasm). Variants of papillary carcinoma can be excluded by the absence of the characteristic nuclear features in almost all cases. Metastatic renal cell carcinomas may mimic Hürthle cell neoplasms, but immunocytochemistry for thyroid transcription factor 1 (TTF-1), which is positive in follicular and Hürthle cells, is negative in the cells of renal cell carcinoma. Medullary thyroid carcinoma shows a dispersed cell pattern and a cytologic appearance that can mimic a Hürthle cells neoplasm. Prominent nucleoli are usually absent in medullary carcinoma. With MGG stains, the granules of Hürthle cells are blue, the ones of the cells of medullary carcinoma are red.

A low power view of a FNA from a Hürthle cell neoplasm (MGG). A pure population of Hürthle cells (MGG). Note the pleomorphism which is apparent even at low power; this is not diagnostic of malignancy as it is a common feature in these neoplasms, whether benign or malignant. In our experience it is rather monomorphism which is more commonly associated with malignancy. In all cases definitive criteria for malignancy are exclusively histological (capsular or vascular invasion). 
A group of rather pleomorphic Hürthle cell (Pap). The pleomorphism is striking, with very large nuclei, prominent nucleoli and multinucleations. The N/C ratio however is not high. 
A follicular group of Hürthle cells (Pap). A cohesive group of cells showing the typical features of Hürthle cells (Pap). Note the dense cytoplasm with well defined borders, vescicular nuclei and prominent nucleoli.
Discohesive Hürthle cells (Pap). Discohesive cells with marked pleomorphism but preserved N/C ratio. Cytoplasm is dense and nuclei are round, often eccentrically placed imparting a "plasmacytoid" appearance. This may mimic medullary carcinoma.
A rather pleomorphic collection of Hürthle cells (MGG) showing pleomorphic nuclei, nucleoli and dense cytoplasm, often containing coarse granules. These are different from the fine granularity of medullary carcinoma.
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