Anna Therese RD
Introduction: Mucinous carcinomas may be pure or mixed, depending
on the cellularity present. They are a slow growing neoplasm, are
usually low grade, with rare axillary lymph node metastases. They
have a better prognosis compared with other invasive carcinomas.
Immunohistochemical studies of mucinous carcinomas regularly
show Estrogen Receptor (ER) and Progesterone Receptor (PR)
positivity and human epidermal growth factor receptor-2 (HER-2)
negativity.
Case Summary: A 54-year-old female consulted due to a gradually
enlarging mass on the upper outer quadrant of her right breast.
Core needle biopsy of the mass revealed an invasive carcinoma
with mucinous features. The patient underwent modified radical
mastectomy, where the final histopathologic diagnosis for the
submitted surgical resection specimen was mucinous carcinoma
with signet ring cell features, Nottingham histologic grade II.
Immunohistochemical staining of the core biopsy specimen and
surgical resection specimen revealed negative estrogen and
progesterone receptors and positive HER2/neu receptor (3+)
in 100% of the tumor cells, which is different from the typical
immunohistochemistry profile of mucinous breast carcinomas.
Discussion: Pure mucinous carcinoma or colloid carcinomas
accounts for not more than 2% of invasive breast carcinomas and
presents with large amounts of extracellular mucin. Between pure
and mixed mucinous carcinoma, prognosis is better in pure types.
Modified radical mastectomy remains the gold standard of treatment
for breast tumors followed by post-operative endocrine therapy,
which is indicated in estrogen and progesterone responsive tumors.
HER2/neu expression in breast tumors along with the absence of
hormone (estrogen and progesterone) receptors is associated with
an aggressive phenotype. When HER-2 is positive, treatment would
be trastuzumab, although resistance for mucinous carcinomas has
been reported.
Conclusion: Only few cases of pure mucinous carcinomas are positive
for HER2 receptors and negative for estrogen and progesterone
receptors. It is important for physicians to know that cases of mucinous
carcinoma positive for HER2 and negative for estrogen and
progesterone exist and to be aware of the clinical problems that they
may present.