Hybrid Intercalated Duct Lesion of the Parotid: Diagnostic Challenges of a Recently Described Entity with Fine Needle Aspiration Findings

Abstract

Intercalated duct lesions (IDL) of the salivary glands are recently described, and encompass both hyperplasia and benign neoplasms that remain incompletely understood. IDLs have been linked to various benign and low-grade malignant salivary gland neoplasms. We herein present a case of a 77 year old woman with an IDL of the parotid composed of both a hyperplastic and an adenomatous component and report, for the first time, the fine needle aspiration findings of such a lesion. This case illustrates the morphologic spectrum of an IDL, as well as challenges in rendering an accurate cytological and histologic diagnosis. The potential diagnostic pitfalls presented by the hybrid pattern of this lesion are also discussed.Keywords Intercalated duct lesion Á Intercalated duct hyperplasia Á Intercalated duct adenoma Á Salivary gland Á Fine needle aspiration cytology Á Parotid Case ReportA 77 year old Malay woman presented with an asymptomatic subcentimeter nodule in the superficial parotid gland. The patient had a history of metastatic papillary thyroid carcinoma (PTC) 17 years prior to presentation that was treated with total thyroidectomy and adjuvant radioactive iodine. At the time of presentation she was undergoing radioactive iodine treatment following surgery for local and nodal recurrent PTC, during which a magnetic resonance imaging (MRI) scan showed an ovoid, enhancing nodule in the left superficial parotid measuring 9 mm (Fig. 1).On examination, a vaguely palpable nodule was present in the left parotid gland. Facial nerve function was preserved. A thyroidectomy scar and previously documented right vocal cord paralysis was noted. There was no palpable cervical lymphadenopathy.Fine needle aspiration biopsy of the parotid nodule was performed. This showed sheets and clusters of basaloid epithelial cells with high nuclear to cytoplasmic ratio (Fig. 2a, c); on high power magnification, the epithelial cells displayed fairly uniform, round to ovoid nuclei (Fig. 2b, d). Small amounts of dense stromal material were seen at the periphery of a few cell clusters (Fig. 2c, d). No plasmacytoid or spindled myoepithelial cells were identified. There was no evidence of high-grade cytological atypia, nuclear features of papillary thyroid carcinoma, or necrotic debris. A cytological diagnosis of a salivary gland basaloid neoplasm was rendered and excision was recommended.A left near-total parotidectomy was performed. On gross examination, the cut surface of the specimen revealed a mostly well circumscribed, firm, homogenously tan-white nodule measuring 0.7 cm (Fig. 3a). Multiple unremarkable intra-and peri-parotid lymph nodes ranging from 0.2 to 0.6 cm were present. Microscopically, there was a partially encapsulated lesion with two components: a nodular component and an adjacent irregular component. The nodular component was composed of closely packed, wellformed tubules with little intervening stroma (Fig. 3b). The tubules were lined by a single layer of cuboidal cells with cytologically bland, rounded nuclei and moderat...

Hybrid intercalated duct lesion of the parotid: A case report

“…According to the largest study to date, describing a total of 32 IDL cases, the female to male sex ratio was 1.7:1 (19 women, 11 men, 2 unknown) and the mean age during diagnosis was 53.8 years[ 1 ]. We have found two other similar papers that report IDL cases originating from the parotid gland as hyperplastic and hybrid forms[ 9 , 10 ]. Mok et al [ 9 ] reported a hybrid form of parotid gland IDL where such lesion for the first time was detected by fine needle aspiration biopsy.…”

“…We have found two other similar papers that report IDL cases originating from the parotid gland as hyperplastic and hybrid forms[ 9 , 10 ]. Mok et al [ 9 ] reported a hybrid form of parotid gland IDL where such lesion for the first time was detected by fine needle aspiration biopsy. They also forewarn potential differential diagnostic pitfalls associated with varied architectural features proposing its’ special awareness during microscopic evaluation.…”

Intercalated Duct Adenoma of the Parotid Gland

“…Intercalated duct lesions are arbitrarily divided into IDA -if encapsulated and discretely separated from adjacent acinar units, and intercalated duct hyperplasia (IDH) -if unencapsulated and blending into the adjacent acinar units. [3][4][5] The ductal cells of IDA resemble those of non-neoplastic intercalated ducts on immunohistochemistry, staining diffusely with CK7 and S100, and focally for ER and lysozyme while CK14 and Calponin highlight the thin myoepithelial cells surrounding the ductal cells. 1,3,4 Immunohistochemical stains for myoepithelial cells were not requested as we felt that the participation of acinar cells in a characteristic manner was sufficiently diagnostic of the entity.…”

“…Basal cell adenocarcinoma importantly demonstrates an invasive growth pattern. 3,5 IDA on the other hand are small and infrequently seen macroscopically, most often measuring less than 5 mm in diameter. 2 Both IDA and IDL in general have an excellent prognosis upon complete surgical excision and recurrences are not reported.…”

Advances in PSMA theranostics

“…Intercalated epithelial cells constitute a relatively minor portion of salivary gland and explains the apparent absence of PSMA in some studies [19 , [91 , 262] . The role of PSMA in the intercalated epithelia cells is not known, but interestingly these cells give rise to neoplasias just as the PSMA expressing cells in the prostate do [263 , 264] .…”