Carcinoma mammario metaplastico (MBC)

È un tipo di tumore molto raro (<1% di tutte le neoplasie mammarie) e aggressivo di carcinoma invasivo della mammella, caratterizzato da punteggio Ki-67 elevato (elevata aggressività e crescita rapida) e dimensioni relativamente grandi, con tendenza alla metastizzazione, in particolare ai polmoni, ossa e cervello, e interessamento relativamente meno frequente dei linfonodi del cavo ascellare.

Dal punto di vista istologico, il tumore presenta cellularità di grado elevato e differenziazione eterologa (da cui la denominazione metastatica), con elementi condroidi, ossei, pleomorfi/sarcomatoidi, fusiformi e squamosi.

Diagnosi: di solito è presente una massa di grosse dimensioni, mobile, ben circoscritta; la massa cresce rapidamente, può essere dolorosa e interessare la parete toracica e la cute, causando ulcerazioni.

Esami strumentali: mammografia, ecografia, aspirazione con ago sottile (FNA), biopsia centrale.

L’esame USG fornirà ulteriori elementi su morfologia ed estensione del carcinoma.

Terapia: il trattamento locale (chirurgia e radioterapia) sono in linea generale uguali agli altri tipi di tumore.

I tumori metaplastici all’esame istologico presentano abitualmente un fenotipo triplo negativi e e frequentemente mutazioni di TP53. Nei carcinomi metaplastici non è perciò indicata né una terapia ormonale né la terapia biologica mirata (terapia a bersaglio) con Trastuzumab (Herceptin®).
La chemioterapia rappresenta perciò il trattamento precauzionale di scelta in questi tumori. I farmaci chemioterapici più utilizzati sono:

• antracicline: doxorubicina (Adriamycin) o l’epirubicina (Ellence)
• taxani: paclitaxel (Taxol) o docetaxel (Taxotere).

Sei cicli di questa chemioterapia da quattro a sei mesi prima dell’intervento chirurgico  che prevede mastectomia totale, lumpectomia ed eventuale linfadenectomia ascellare in caso di positività del linfonodo sentinella.

È importante sottolineare che esistono due sottotipi di carcinoma metaplastico che presentano bassi livelli di aggressività, ovvero il carcinoma tipo-fibromatoso e il carcinoma adenosquamoso di basso grado. Da un punto di vista istologico i carcinomi fibromatosis-like a cellule fusate devono essere distinti dalla fibromatosi desmoide e altre forme benigne a cellule fusate della mammella, che seppure siano meno aggressivi dei carcinomi metaplastici, hanno tuttavia a lungo termine un potenziale metastatico e devono essere trattati chirurgicamente come carcinomi.

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