Fine needle aspiration cytology of metastatic polymorphous low‐grade adenocarcinoma of the palate in a cervical lymph node

Dear Editor, Polymorphous low-grade adenocarcinoma (PLGA) is well recognized as a major type of minor salivary gland neoplasm, almost 60% occurring in the palate. Although PLGA is described as the commonest intraoral malignant salivary gland tumour, comprising 26% of all carcinomas, it is especially rare in the Japanese population. PLGA has a distinct natural history characterized by slow and indolent growth, with late development of cervical lymph node metastasis and often distant recurrence. Cervical lymph node metastasis of PLGA is present in nearly 5% of cases at diagnosis and occurs in 10% during long follow-up after the initial surgery. Different cytological features in two lymph node metastases are reported with their differential diagnosis. A 70-year-old Japanese man with a history of PLGA of the palate underwent resection of the tumour and partial removal of the upper jawbone in 2000. We have previously reported the primary cytomorphological features of PLGA in this patient. The patient was followed after surgery: a cervical palpable mass was noted after 6 years and again 8 years later. Clinical examination revealed a firm rubbery mass in the cervical lymph node. Fine needle aspiration cytology (FNAC) was performed on each occasion, and subsequent resection of cervical lymph nodes. There has been no recurrence during the following 3 years. The first FNAC smear of the cervical lymph node metastasis showed high cellularity, with a moderate to large number of papillary clusters (Figure 1a). The clusters contained overlapping metachromatic hyaline globules on May-Grünwald–Giemsa staining, as seen in adenoid cystic carcinoma, with similar material in the background (Figure 1b). The tumour cells had a light green cytoplasm on Papanicolaou staining with slightly irregular nuclei and small nucleoli. No mitotic figures were observed. On the FNAC of a second cervical lymph node matastasis, serous fluid was (a)