Secretory carcinoma of salivary type in a lymph node presenting as a neck cyst diagnosed by cytology: A case report.

Secretory carcinoma (SC) is a relatively recently described salivary gland adenocarcinoma characterized by ETV6-NTRK3 gene fusion and, in most cases, indolent clinical behavior. Morphologically, the tumor shows a glandular architecture and the presence of monophasic tumor cells with vacuolated cytoplasm, low-grade nuclear atypia, and mucin production, with possibly a tubular, papillary, or cystic arrangement. In this article, we describe a case of a 52-year old man with SC involving a neck lymph node clinically manifesting as a slowly growing cystic neck mass without recent proof of the primary tumor, but with a history of a parotid gland "cystadenopapilloma," which had been removed 35 years prior. A fine-needle aspiration biopsy revealed a diagnosis of SC. Subsequent histopathological examination after lymph node dissection confirmed the diagnosis. The tumor showed typical features of SC, including immunohistochemical positivity for NTRK and NTRK3 gene rearrangement, detected using in situ hybridization. We discuss that the tumor may be a late metastasis occurring 35 years after resection of undiagnosed salivary SC or a primary SC arising from heterotopic salivary tissue within a lymph node. Differential diagnostic considerations and review of relevant literature are included.