Intraductal carcinoma of right parapharyngeal space presenting as a fluctuant swelling of retromolar region: Case emphasizing on the histological differential diagnosis

Deepak Pandiar; Pratibha Ramani; Murugesan Krishnan; Reshma P Krishnan

doi:10.4103/jomfp.jomfp_288_22



CASE REPORT

Year : 2023 \| Volume : 27 \| Issue : 5 \| Page : 28-32

Intraductal carcinoma of right parapharyngeal space presenting as a fluctuant swelling of retromolar region: Case emphasizing on the histological differential diagnosis

Deepak Pandiar¹, Pratibha Ramani¹, Murugesan Krishnan², Reshma P Krishnan¹
¹ Department of Oral Pathology and Microbiology, Saveetha Dental College and Hospitals, Chennai, Tamil Nadu, India
² Department of Oral and Maxillofacial Surgery, Saveetha Dental College and Hospitals, Chennai, Tamil Nadu, India

Date of Submission	02-Jun-2022
Date of Decision	08-Sep-2022
Date of Acceptance	08-Sep-2022
Date of Web Publication	04-Feb-2023

Correspondence Address:
Deepak Pandiar
Department of Oral Pathology and Microbiology, Saveetha Dental College and Hospitals, Chennai, Tamil Nadu
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jomfp.jomfp_288_22

Abstract

Intraductal carcinoma (IDC) of salivary gland is an extremely rare malignancy affecting mainly the parotid glands. Intraoral occurrence is seen mainly on the palate where the tumour arises from the minor salivary glands. No previous case has been described in parapharyngeal space. We report a case of low-grade IDC of the anterior compartment of the right parapharyngeal space that clinically resembled a lesion of vascular origin. Due to the extreme rarity of intraductal carcinoma, it may not be considered by dentists and dental specialists in clinical differential diagnoses, leading to delay in treatment. Intraductal carcinoma must be differentiated from its close histological but high-grade mimickers to avoid unnecessary overtreatment and better patient outcome.

Keywords: Carcinoma, intraductal, parapharyngeal, salivary gland

How to cite this article:
Pandiar D, Ramani P, Krishnan M, Krishnan RP. Intraductal carcinoma of right parapharyngeal space presenting as a fluctuant swelling of retromolar region: Case emphasizing on the histological differential diagnosis. J Oral Maxillofac Pathol 2023;27, Suppl S1:28-32

How to cite this URL:
Pandiar D, Ramani P, Krishnan M, Krishnan RP. Intraductal carcinoma of right parapharyngeal space presenting as a fluctuant swelling of retromolar region: Case emphasizing on the histological differential diagnosis. J Oral Maxillofac Pathol [serial online] 2023 [cited 2023 Mar 24];27, Suppl S1:28-32. Available from: https://www.jomfp.in/text.asp?2023/27/5/28/369175

Introduction

First described in 1996 by Delgado and colleagues, intraductal carcinoma (IDC) is an extremely rare malignancy of the salivary glands mainly affecting the parotid gland and intraparotid lymph nodes characterized histologically by intracystic/intraductal proliferations of neoplastic epithelial cells.^[1] After parotid and intra-parotid nodes, palate, submandibular glands, minor salivary glands and masseter muscles are affected in the same descending order.^[1] The lesion has been described under a variety of terms in the literature including 'low grade salivary duct carcinoma' and 'low grade cribriform cystadenocarcinoma' but intraductal carcinoma has been adopted by the latest WHO classification of head and neck tumours.^[2] Based on degrees of cytological abnormalities, the lesions may be subcategorised into low grade, intermediate grade and high grade.

The tumour has not been previously described in parapharyngeal space (PPS). PPS is anatomically divided into anterior (pre-styloid) and posterior (post-styloid) compartments.^[3] For ease of understanding the lesions of the pre-styloid PPS compartment may be categorized based on the tissue of origin, however, lesions of the post-styloid compartment extending anteriorly may not be completely excluded. Pre-styloid compartment lesions mainly arise from salivary glands (deep lobe of parotid and oral minor salivary glands), lymph nodes and parapharyngeal fat.^[3] Posterior compartment lesions arise from major vessels, cranial nerves, lymph nodes and glomus tissue. The aim of the present case was to describe a rare and first case of low-grade-IDC in the pre-styloid compartment of PPS clinical presenting as a fluctuant retromolar swelling clinically resembling a vascular lesion.

Case Report

A 25-year-old Dravidian Indian female presented with a chief complaint of swelling in the right lower back tooth region for 1 month. On clinical examination, there were no remarkable extra-oral findings. Intra-orally, a 4 × 4-cm sized fluctuant, translucent, mildly tender smooth-surfaced swelling was noted in the right retromolar region centred more lingually, obliterating the right posterior lingual sulcus [Figure 1]. There were clearly visible surface telangiectatic vessels. The swelling was soft in consistency and mildly tender on palpation. Computed tomographic and magnetic resonance imaging showed multi-lobulated cystic spaces with a mild mass effect on the right parapharyngeal space (PPS).

Figure 1: Clinical presentation of the lesion demonstrating a translucent swelling with prominent surface vessels

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Considering the clinical features and imaging findings, fine needle aspiration cytology (FNAC) was attempted yielding a dirty brown fluid which under microscopy showed mucous cells, few squamous cells and papillaroid arrangement of hyperchromatic cells in a mucinous background. Based on these findings, salivary gland tumour was considered. On incisional biopsy, low-grade mucoepidermoid carcinoma, cystadenoma and sclerosing polycystic adenosis were considered and excision of the specimen was advised with the evaluation of margins on frozen sections.

A crestal incision was made over the area distal to the right mandibular third molar. A capsulated lesion was seen located extending from the lingual aspect of the third molar to the pre-styloid compartment of the parapharyngeal space. Intra-operatively, mucinous material was noted extruding from the cystic lesion. The lesion was excised in toto. H&E-stained frozen section demonstrated one focus showing close apposition with skeletal muscle but resected margins were free of tumour. Wound closure was done using vicryl 3-0 suture material.

The excised specimen showed an unencapsulated tumour mass composed of glandular epithelium in a fibrous and hyalinized stroma. The epithelium was arranged mainly as numerous large cystic structures admixed with tubular and solid areas. The cystic spaces were lined mainly by double-layered epithelium showing mild atypia, micro-papillary projections and focal 'Roman Bridge' architecture [Figure 2]. The cystic spaces were filled with abundant PAS and Alcian Blue positive eosinophilic material. There was no stromal invasion throughout the tumour. Few areas showed mucinous and apocrine features.

Figure 2: Photomicrographs of H&E-stained sections showing (a) large mucin-filled cystic space with an intraductal epithelial proliferation of tumour cells in a fibrous stroma (40X), (b and c) micro-papillary and 'Roman bridge' architecture, and (d) cystic space lined by a single layer of cuboidal cells (100X)

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A panel of immunohistochemical markers was done. CK7 was seen diffusely positive in the cytoplasm of tumour cells [Figure 3]a. p63 demonstrated a rim of intact myoepithelial cells [Figure 3]b. Ki-67 showed a proliferation index of <1%. S100, ER, PR, AR and Her2neu showed no immunoreactivity. A final diagnosis of intraductal carcinoma- low grade (L-IDC) was made. Ultrasonographic and mammographic studies showed no identifiable lesion elsewhere in the body. There was uneventful healing. The patient is being regularly followed-up for the past 1 year with no signs of recurrence.

Figure 3: Photomicrographs of IHC-stained sections showing (a) diffuse cytoplasmic positivity for CK7 and (b) rim of p63 positive myoepithelial cells demonstrating no stromal invasion

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Discussion

Head and neck region comprises many complex spaces housing for a variety of non-neoplastic and neoplastic lesions. Parapharyngeal space is a unique inverted pyramidal-shaped anatomical space situated in the supra-hyoid neck. The base is formed by the base of the skull and the apex points the greater cornu of the hyoid bone. As aforementioned, PPS is divided into pre-styloid (anterior) and post-styloid (posterior) compartments by a fascia traversing from the styloid process of the temporal bone to the tensor veli palatini muscle.^[3] PPS contains various structures including salivary, neural, fatty, lymphoid and vascular tissues, therefore, a wide variety of non-neoplastic and neoplastic lesions can potentially arise in this region.^[4],[5]

IDCs are usually well-circumscribed but non-encapsulated and show three possible patterns.^[6] Our case showed a combination of all these histological patterns. Clinical, cytological and histological presentations were deceptive and a final diagnosis could be rendered only after excision. Various authors have further sub-classified IDC as apocrine type and intercalated type. The former subtype is AR positive with/without abundant granular eosinophilic cytoplasm, large nucleoli, apocrine snouts and secretions. The intercalated subtype is S100 + and shows small eosinophilic to amphophilic cuboidal cells.^[2] It was not possible to sub-categorise the present case in either of these above-named categories. Attempts have also been made to classify on the basis of stromal invasion and percentage and extent of cell type component (apocrine/intercalated). As IDC is very rarely encountered, it may be difficult to correctly categorize IDC unless more cases/studies are published correlating the impact of histological sub-typing on disease outcome. Our case was an admixture of histological architectures, with both apocrine and intercalated features and no evidence of stromal invasion. The histological differential diagnoses for L-IDC have been tabulated in [Table 1].

Table 1: Depicting comparison of intraductal carcinoma with its closest histological mimickers

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Owing to the extreme rarity of IDC, there are no universal criteria for diagnosis of intraductal carcinoma and more importantly, there is lack of clarity on the role and correlation of distinction between low-grade and high-grade variants with patient outcomes. It has been found that pleomorphism, stromal invasion and high-grade morphologic and molecular features are frequently associated with apocrine changes with no clear association of pleomorphism with intercalated cells or oncocytes. Further, there are no reliable immunohistochemical markers that can clearly distinguish the high-grade variants from low-grade ones. In such cases, the application of a proliferative marker may be fruitful. In the present case, using ki-67, we found a proliferative index of <1%. The mitotic count may not be a reliable indicator. Thus, we propose that the following points must be considered for reporting IDC in the future: (a) determination of stromal invasion (p63 or S100 may be employed), (b) percentage of apocrine and intercalated cells (may be subjected to intra-tumoural and interobserver variability), (c) proliferation index as assessed by Ki-67, (d) extent of cellular pleomorphism/atypia and presence or absence of necrosis, (e) AR and S100 immunoreactivity for sub-categorization into AR+/S100 + types, (f) molecular analysis and (g) long-term follow-up to correlate any of the above-mentioned features with the outcome.

Only a few case reports and series have reported and analyzed molecular rearrangements. RET rearrangement has been documented and there was a difference in translocation partner in low-grade IDC with intraductal immunophenotype and high-grade IDC showing apocrine features. NCOA4 is the most common partner in the former while the latter shows TRIM27-RET fusion.^{[7],[8],[9],[10]} Rare cases of IDC with invasive growth patterns have recently shown novel TUT1:ETV5, KIAA1217:RET and STRN: ALK fusions. Recurrences have been reported and mainly depend on the surgical margins and/or tumour focality (unifocal/multifocal).^[2] Complete surgical excision with clear margins is the treatment of choice. Submission of the complete specimen and extensive sampling should be done to determine the predominant cell type, stromal invasion and multifocality. Long-term follow-up is mandatory.

Conclusion

At times, the clinical presentation of IDC is deceptive and may resemble a lesion of vascular or neurogenic origin particularly in parapharyngeal space. A careful evaluation aided by imaging findings should be done but the final diagnosis may be rendered only after histopathological examination and immunohistochemical characterization. IDC must be differentiated from its close histological but high-grade mimickers to avoid unnecessary overtreatment and better patient outcome.

Authors' declaration

All authors have read and reviewed the manuscript and have given consent for submission.

Consent for publication

Appropriate consent was taken from the patients for including the intraoral photograph; and the patients are aware that their identity shall remain anonymous.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given her consent for images and other clinical information to be reported in the journal. The guardian understands that her names and initials will not be published and due efforts will be made to conceal the patient's identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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