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Orbital metastasis from a primary salivary duct carcinoma: importance of long-term follow-up

      Introduction

      Primary salivary duct carcinoma (SDC) of the parotid gland is a relatively uncommon tumour. Amongst the noted cases in the literature, metastasis of the primary SDC is known to involve the lungs, liver, bones, lymph nodes, gingiva, vagina, and rarely the orbit.
      • Saleh T.A.
      • Hakin K.N.
      • Davidson M.J.
      Metastasis of acinic cell carcinoma of the parotid gland to the contralateral orbit.
      • Parikh J.G.
      • Burnstine M.A.
      • Kase S.
      • Rao N.A.
      Salivary duct carcinoma metastatic to eyelid and orbit-a case report.
      • Saxena R.B.
      • Mathur R.N.
      • Sonani S.Z.
      Orbital metastasis of mixed parotid tumour.
      • Thomas K.M.
      • Cumberworth V.L.
      • McEwan J.
      Orbital and skin metastases in a polymorphous low-grade adenocarcinoma of the salivary gland.
      The reported cases of orbital metastasis from a primary SDC have shown a good prognosis, whenever appropriate intervention was instituted at the earliest. In this report, we describe the clinical difficulties, investigations, and management of a metastatic SDC of the orbit that presented prior to manifestations at the primary location.

      Case Description

      A 56-year-old male patient presented with history of pain, redness, and congestion along the left medial canthus for the past four weeks. Past history revealed a presumptive diagnosis of extraocular muscle cysticercosis that was based on prior clinical and equivocal ultrasonographic findings.
      However, there was no prior history of any ocular trauma, surgery, or any known systemic illness. Examination done in our oculoplastic clinic revealed severely restricted extraocular motility in all the gazes (Fig. 1). Visual acuity was 20/20 OD and light perception with accurate projection of rays in the left eye. There was evident congestion involving the left caruncle, bulbar, and forniceal conjunctiva. However, the cornea remained clear with minimal anterior chamber distortion or inflammation. Using Goldmann applanation tonometry, intraocular pressures were noted as 16 mm Hg OD and 32 mm Hg OS. Dilated fundus examination revealed prominent chorioretinal folds along the nasal retina in presence of a healthy disc and macula.
      Fig. 1
      Fig. 1Clinical profile at presentation showing congested left eye with severe restriction of extraocular movements in all directions.
      Routine haematological investigations including complete hemogram and liver and kidney function tests were essentially within normal limits. Orbital B scan ultrasound revealed a fairly well defined homogenous soft tissue mass lesion occupying the medial orbital space; however, the medial rectus muscle belly could not be identified separately in terms of its relationship with the mass lesion, thus suggesting a probable engulfment of the muscle by the mass lesion. To further delineate the anatomical extent of the tumour, a contrast-enhanced computed tomography of the orbit was performed. It revealed a heterogeneously enhancing well-defined oval mass lesion with a central hypoechoic area lying along the medial orbital wall. The tumour measured around 14–18 mm in its greatest antero-posterior and horizontal dimensions, as seen on axial and coronal sections. Laterally the mass lesion was indenting the globe, which correlated with the fundus examination (Fig. 2A,B). However, the medial rectus muscle belly could be appreciated only from the posterior aspect of the mass up to the orbital apex. To look for any additional foci of the tumour mass, a whole body positron emission tomography (PET) scan was performed, which showed a localized metabolically active lesion within the left orbit with no additional foci in the body (Fig. 2C,D). Based on these evident clinical findings, a presumptive diagnosis of a primary orbital pathology was made and an orbital biopsy was performed under local anesthesia for histopathological assessment of the mass lesion. This turned out to be a metastatic salivary duct carcinoma.
      Figs. 2
      Fig. 2A and B. Coronal and axial sections of contrast-enhanced computed tomography revealing a well-defined mass along the medial orbit with significant globe indentation and lateral displacement. C and D. Coronal and axial sections of positron emission tomography (PET) showing a significant metabolically active lesion along the original mass.
      Following histopathological confirmation, keeping in mind the aggressive nature of the tumour, a total orbital exenteration was performed under general anaesthesia. The specimen under the microscope showed tumour cell infiltration along the orbital fat, with marked desmoplastic reaction. The infiltrating tumour cells were in the form of small ductules and small groups with abundant granular cytoplasm and vesicular nuclei (Fig. 3A). These tumour cells were seen along the medial aspect of the globe extending into the outer ocular coats with a posterior continuation, thus invading the proximal part of the optic nerve. Immunohistochemistry showed positive reactivity for epithelial membrane antigen (Fig. 3B) and cytokeratin 7, suggestive of a salivary duct carcinoma. Postoperatively patient received palliative radiotherapy; a total dose of 75cGy was given over a period of 3 months in 20 divided doses. The patient remained asymptomatic for 18 months, after which he developed a swelling over the left parotid region. A biopsy revealed findings consistent with the previous orbital mass lesion, suggestive of a dormant primary in the left salivary gland (Fig. 3C). For this primary tumour, patient underwent repeated detailed evaluation clinically as well as radiologically in the form of a whole body PET scan. Fortunately, the tumour did not show any further metastasis; thus for the primary tumour patient underwent surgery to remove the primary foci in total.
      Fig. 3
      Fig. 3A. High-power view demonstrating tumour cells infiltrating fibrous tissue (H&E X200). B. Immunohistochemistry showing strong cytoplasmic positivity for epithelial membrane antigen and cytokeratin 7 in tumour cells (Avidin-Biotin X200). C. Clinical picture at 18 months’ follow-up showing a newly developed mass lesion at the site of the left parotid gland.

      Discussion

      Common malignant salivary gland tumours include mucoepidermoid carcinoma, adenoid cystic carcinoma, adenocarcinoma, malignant mixed tumour, acinic cell carcinoma, and others. Of these, orbital metastases from acinic cell carcinoma, adenoid cystic carcinoma, and salivary duct carcinoma have been previously reported in literature. Saleh et al. noted a case of acinic cell carcinoma metastasizing to the contralateral orbit, submandibular glands, and submandibular lymph nodes: This is a low-grade malignant tumour affecting males more often, with unilateral involvement. At the end of 11 months follow-up, the patient remained stable without any recurrences.
      • Saleh T.A.
      • Hakin K.N.
      • Davidson M.J.
      Metastasis of acinic cell carcinoma of the parotid gland to the contralateral orbit.
      Similarly, Parikh et al. reported a case of salivary duct carcinoma metastasizing to the left lower eyelid and the anterior orbit. In this case, a right sided parotid salivary duct carcinoma was detected 6 years prior to the metastatic manifestations; however, the authors only discussed the histopathology and immune histochemical aspects of the ductal tumours—they did not mention the outcome of the disease in that patient.
      • Parikh J.G.
      • Burnstine M.A.
      • Kase S.
      • Rao N.A.
      Salivary duct carcinoma metastatic to eyelid and orbit-a case report.
      Similarly, there are two other reports describing the orbital metastasis in case of a mixed parotid tumour and polymorphous low-grade adenocarcinoma of the parotid glands.
      • Saxena R.B.
      • Mathur R.N.
      • Sonani S.Z.
      Orbital metastasis of mixed parotid tumour.
      • Thomas K.M.
      • Cumberworth V.L.
      • McEwan J.
      Orbital and skin metastases in a polymorphous low-grade adenocarcinoma of the salivary gland.
      After orbital exenteration, the examination of the specimen under the microscope revealed a larger poorly differentiated tumour mass eroding the ocular coats with a posterior extension invading the proximal part of the optic nerve; however, the resected posterior end of the optic nerve and rest of the margins were free of tumour cells. Immunological stains for cytokeratin, epithelial membrane antigen, and cytokeratin 7 were positive, whereas reactivity for S-100 proteins, estrogen receptors, progesterone receptors were negative. To conclude, the primary salivary duct carcinoma of the salivary gland remained asymptomatic clinically as well as radiologically for 18 months. Thus orbital tumours with unusual presentations need a detailed evaluation with close follow-up to counter the problems related to a primary tumour elsewhere in the body at the earliest, thereby helping to reduce systemic morbidity and mortality.

      Disclosure

      The authors have no proprietary or commercial interest in any materials discussed in this article.

      Conflicts of interest

      None.

      Acknowledgments

      none
      Funding support None
      Authors contribution All authors contributed equally.

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