Neuroendocrine differentiation in breast carcinoma with osteoclast-like giant cells. Report of a case and review of the literature

Osteoclast-like giant cells (OGCs) may occur in several types of breast carcinomas (BS). Neuroendocrine differentiation may be present in BS but, associated with OGCs, neuroendocrine differentiation has been rarely reported. A case of invasive ductal carcinoma with OGCs and neuroendocrine differentiation diagnosed by fine needle cytology (FNC) is described. A 72-year-old woman with a nodular lesion of the right breast underwent to fine-needle cytology (FNC) The smears showed a dissociated cell population of monomorphous, mononucleated atypical cells with interspersed multinucleated giant cells osteoclast-like. The mononuclear cell component showed plasmacytoid features and frequent vacuoles of secretion. Immunostaining (IHC) performed on cell block sections showed oestrogen receptor positivity in the mononucleated cells and OGCs positivity for LCA and CD68. Histologically the tumour showed cell nests or cords separated by thin fibrovascular septa. The neoplastic cells were monomorphic, with round-oval nuclei, granular chromatin and evident nucleoli. The cytoplasm was indistinct and eosinophilic, finely granular, often containing eosinophilic globules that were positive at the PAS and mucicarmine stainings. Numerous non-neoplastic OGCs were also detected in the interstitial septa. The ICH showed positivity of the tumoral cells for E-Cadherin, oestrogen and progesterone receptors and c-ErbB2 negativity. Mitotic index was inconspicuous with a low Ki67 positivity rate (<10%). OCGs were CD68 and LCA positive. IHC also showed strong positivity for the chromogranin and synaptophysin. A diagnosis of invasive ductal BC with OGCs and neuroendocrine differentiation was performed. The expression of chromogranin and synaptophysin was then retrospectively assessed on CB sections too. The identification of OGCs component on breast FNA samples is not difficult, depending on a good sampling only. On contrary, the neuroendocrine differentiation still represents still a challenge in breast FNC.