Case History
Twenty-seven years old female presented to the cytology clinic with the submandibular swelling for the past three months. The patient was a known case of pleomorphic adenoma post-surgery in the same region six years back. On examination, one nodular swelling with an irregular surface measuring 1 x 1 cm was appreciated beside the scar site. The other swelling, almost of the same measurement, was seen in the left level III lymph node region (Figure 1 A). Both the lumps were firm mobile and painless. A non-guided fine needle aspiration cytology (FNAC) was performed from both the lumps. Papanicolaou- and May-Grünwald Giemsa-stained smears were moderately cellular shows clusters as well as dispersed plasmacytoid cells and few ductal epithelial cells with patchy stromal matrix in the background. (Figure 1 B). Aspirate smears from the lymph node showed similar morphology.(Figure 1 B, C, D) No evidence of atypia/malignancy was appreciated in the smear studied from both the sites. Informed consent was obtained from patient for reporting this case.
Discussion
This case was reported as recurrent pleomorphic adenoma at the primary and benign metastatic deposits in the lymph node which is confirmed on ultrasonography. The diagnosis was based on presence of plasmacytoid myoepithelial cells and benign ductal epithelial cells with no atypia in a background of fibrillary chondromyxoid material at both the sites. When we see relatively bland/benign-looking foreign cells in a node should consider two possibilities. First, is it a benign epithelial inclusion in the node or second a chance of a benign metastasizing tumour. The benign epithelial lesions that can be observed in the lymph node include epithelial inclusion cysts, which are also called benign metastasis or heterotopia. The sites include Axillary, cervical, mediastinal, mesenteric, para-aortic, pelvic, renal lymph nodes.1 Different theories regarding the pathogenesis of inclusions are reported in the literature, which includes benign metastasis, developmental heterotopia, and metaplasia of multipotent cells, iatrogenic displacement, and transport.1 Examples of benign tissue include salivary gland, thyroid follicles, breast tissue, respiratory type epithelium, fallopian tube lining, or endometrium. Single or tubules of epithelial cells in sub capsular sinus of draining lymph node after surgical or needle manipulation.1 In cervical lymph nodes, the common epithelial inclusions include thyroid, salivary gland tissue, and squamous epithelium. We kept that possibility, but in our case, we had a history of surgery for Pleomorphic adenoma, and there was a recurrence at that site. The appreciation of epithelial cells, myoepithelial cells, and the chondromyxoid fibrillary matrix also made us conclude metastatic pleomorphic adenoma ahead of epithelial inclusion.
Pleomorphic adenoma is the most common benign salivary gland tumour. The metastases are observed more frequently in bones, lungs, and lymph nodes.2 There are several hypotheses about the aetiology of the metastasis of benign tumours and the recurrence. It is believed that the enucleation of the pleomorphic adenoma may be incomplete, contributing to recurrence. At the same time, vascular implantation of tumour cells during surgery can occur, leading to dissemination by the haematogenous route, which could be the possible hypothesis in our case. In cases with nodal metastasis, the other possibility that should be considered is malignant transformation (carcinoma ex Pleomorphic adenoma) at the recurrence site and a metastatic deposit in the lymph node. However, in our case, there was adequate cellularity in smears of both sites without any recognizable features of malignancy (Lack of rapid growth/cellular atypia/frequent mitotic figures/ necrosis).
This case helps in reminding the cytologists of the list of some benign tumours which can metastasize such as pleomorphic adenoma, leiomyoma, giant cell tumour of bone 4 and meningioma.3, 4, 5 This article implies the importance of cytology in early diagnosis of the rare phenomenon.
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