Metastasis to the sublingual gland of metaplastic breast carcinoma – a case report

Metastatic spread to the salivary glands is rare, occurring primarily from head and neck tumors to the parotid gland. So far, only one sublingual gland metastasis has been reported in the literature. We herein report the second case of metastasis to this gland occurring in a woman in her 50s, previously diagnosed with HER2-positive metaplastic breast carcinoma (MpBC) with chondroid differentiation, with lymph node and diffuse organ metastases. The sublingual lesion presented as a tumefaction on the floor of the mouth, causing masticatory discomfort. Histologically it was formed by epithelial cells with high-grade cytomorphological features with a large central area of chondroid differentiation. The case was clinically and pathologically challenging, given the rarity of the primary MpBC and the improbable secondary location. Alternative primary salivary gland tumors with chondroid differentiation were considered, but ultimately the clinical integration was crucial in establishing the diagnosis of MpBC metastasis to the sublingual gland.