cancers Article MR and CT Imaging of the Normal Eyelid and its Application in Eyelid Tumors 1, , 2, 3 1,4 Teresa A. Ferreira * y, Carolina F. Pinheiro y , Paulo Saraiva , Myriam G. Jaarsma-Coes , Sjoerd G. Van Duinen 5, Stijn W. Genders 4, Marina Marinkovic 4 and Jan-Willem M. Beenakker 1,4 1 Department of Radiology, Leiden University Medical Centre, Albinusdreef 2, 2333 ZA Leiden, The Netherlands; [email protected] (M.G.J.-C.); [email protected] (J.-W.M.B.) 2 Department of Neuroradiology, Centro Hospitalar e Universitario de Lisboa Central, Rua Jose Antonio Serrano, 1150-199 Lisboa, Portugal; [email protected] 3 Department of Radiology, Hospital da Luz, Estrada Nacional 10, km 37, 2900-722 Setubal, Portugal; [email protected] 4 Department of Ophthalmology, Leiden University Medical Centre, Albinusdreef 2, 2333 ZA Leiden, The Netherlands; [email protected] (S.W.G.); [email protected] (M.M.) 5 Department of Pathology, Leiden University Medical Centre, Albinusdreef 2, 2333 ZA Leiden, The Netherlands; [email protected] * Correspondence: [email protected] Co-first author. y Received: 17 January 2020; Accepted: 24 February 2020; Published: 12 March 2020 Abstract: T-staging of most eyelid malignancies includes the assessment of the integrity of the tarsal plate and orbital septum, which are not clinically accessible. Given the contribution of MRI in the characterization of orbital tumors and establishing their relations to nearby structures, we assessed its value in identifying different eyelid structures in 38 normal eyelids and evaluating tumor extension in three cases of eyelid tumors. As not all patients can receive an MRI, we evaluated those same structures on CT and compared both results. All eyelid structures were identified on MRI and CT, except for the conjunctiva on both techniques and for the tarsal muscles on CT. Histopathology confirmed the MRI findings of orbital septum invasion in one patient, and the MRI findings of intact tarsus and orbital septum in another patient. Histopathology could not confirm or exclude tarsal invasion seen on MRI on two patients. Although imaging the eyelid is challenging, the identification of most eyelid structures is possible with MRI and, to a lesser extent, with CT and can, therefore, have an important contribution to the T-staging of eyelid tumors, which may improve treatment planning and outcome. Keywords: eyelid tumors; T-staging; eyelid anatomy; tarsus; orbital septum; MRI; CT 1. Introduction The eyelids correspond to the anterior limit of the orbits. They are muscular-membranous structures [1], forming part of the protective system of the eye. The eyelids have complex anatomy, with each eyelid being constituted of three externally visible regions, namely the external skin, the internal palpebral conjunctiva, and the eyelid margin, all well evaluated with a physical examination. Histologically, however, seven structures [1] are identified in both eyelids, of which the deep structures are not amenable to physical evaluation. The most anterior structure of each eyelid is the skin. Behind the skin, there is the first layer of loose connective tissue. The third layer is the orbicularis oculi muscle, composed of skeletal muscle fibers. The fourth layer, lying behind the orbicularis oculi muscle, is a second layer of loose connective tissue. The fifth layer of each eyelid is a fibro-elastic layer, centrally Cancers 2020, 12, 658; doi:10.3390/cancers12030658 www.mdpi.com/journal/cancers Cancers 2020, 12, 658 2 of 16 Cancers 2020 2 of 15 formed by the tarsal plate and peripherally formed by the orbital septum. The tarsal plate is a firm septum.plate composed The tarsal of denseplate is connective a firm plate tissue composed that helps of todense maintain connective the eyelid tissue shape that buthelps also to containing maintain thesebaceous eyelid glandsshape but called also the containing meibomian sebaceous glands. The glands superior called tarsus the meibomian is 8–12 mm inglands. height T andhe superior attaches tarsusto the is superior 8–12 mm tarsal in height muscle. and The attaches inferior to tarsusthe superior is smaller, tarsal only muscle. 3–4 mmThe ininf height,erior tarsus and attachesis smaller to, onlythe inferior 3–4 mm septum in height and, and inferior attaches tarsal to muscle. the inferior The orbitalseptum septum and inferior maintains tarsal the muscle. intraorbital The orbital fat in septumplace and maintains is involved the inintraorbital the ocular fat and in palpebralplace and movementsis involved in [2 ].the The ocular orbital and septum palpebral of both movements superior [2]and. The inferior orbital eyelids septum attaches of both peripherally superior and to inferior the orbital eyelids rim attaches bone, where peripherally it is continuous to the orbital with rim the boneperiosteum, where [3it]. is Centrally continuous the with orbital the septum periosteum attaches [3]. toCentrally the junction the orbital of the inferiorseptum tarsalattaches muscle to the to junctionthe tarsal of plate the ininferior the lower tarsal eyelid muscle and to to thethe levatortarsal plate palpebrae in the aponeurosis lower eyelid in theand upper to the eyelid levator [1]. palpebraeInferiorly toaponeurosis its attachment in the to the upper superior eyelid orbital [1]. septum,Inferiorly the to levator its attachment palpebrae to aponeurosis the superior fuses orbital with septum,the anterior the levator aspect ofpalpebrae the superior aponeurosis tarsal plate fuses [4]. with Posteriorly, the anterior on the aspect most of cranial the superior part of tarsal the levator plate [4]palpebrae. Posteriorly, aponeurosis on the most and cranial at its junction part of withthe levator the levator palpebrae palpebrae aponeurosis muscle and [4], liesat its the junction “V” shaped with thesuperior levator transverse palpebrae (Whitnall) muscle [4] ligament., lies the The“V” sixthshaped layer superior of the eyelidstransverse consists (Whitnall) of the tarsalligament. muscles, The sixthcomposed layer of smooththe eyelids muscle consists fibers, of actingthe tarsal as eyelid muscles, retractors. composed The of superior smooth tarsal muscle muscle, fibers, also acting known as eyelidas the retractors. Müller’s muscle, The superior inserts tarsal superiorly muscle, at also the known junction as of the the Müller levator's muscle, palpebrae inserts aponeurosis superiorly and at thelevator junction palpebrae of the muscle levator and palpebrae attaches inferiorly aponeurosis to the and superior levator margin palpebrae of the superiormuscle tarsaland attaches plate [1]. inferiorlyThe inferior to the tarsal superior muscle margin inserts of superiorly the superior at the tarsal junction plate of [1] the. The inferior inferior tarsal tarsal plate muscle and inferiorinserts superiorlyseptum, and at the inferiorly junction attaches of the inferior to the fascia tarsal surrounding plate and inferior the inferior septum, rectus and muscleinferiorly [1]. attaches The most to theposterior fascia layersurrounding of the eyelid the inferior is the palpebral rectus muscle or tarsal [1] conjunctiva.. The most posterior The conjunctiva layer of willthe reflecteyelid onis th thee palpebraleyeball as or bulbar tarsal conjunctiva, conjunctiva which. The isconjunctiva not part of will the eyelidreflect (Figure on the1 ).eyeball as bulbar conjunctiva, which is not part of the eyelid (Figure 1). FigureFigure 1. 1. SchematicSchematic cross cross-section-section of of the the eyelids eyelids and and anterior anterior orbital orbital anatomy. anatomy. EyelidEyelid malignanciesmalignancies can can arise arise from from any any of the of eyelidthe eyelid structures, structures but most, but are most of cutaneous are of cutaneous origin [5]. originThe most [5]. commonThe most skin common eyelid tumorskin eyelid is the tumor basal cellis the carcinoma basal cell (BCC), carcinoma followed (BCC) by squamous, followed cellby squamouscarcinoma cell (SCC), carcinoma sebaceous (SCC) cell, carcinoma,sebaceous cell Merkel carcinoma, cell carcinoma, Merkel andcell malignantcarcinoma, melanoma and malignan [5–7t]. melanomaEyelid malignancies [5–7]. Eyelid require malignancies specific deliberations require specific as the deliberations functional andas the esthetical functional impact and ofesthetical surgical impacttreatment of surgical can be devastating treatment can [6]. be devastating [6]. AccurateAccurate staging staging of of an an eyelid eyelid tumor tumor is is based based on on the the Tumor, Tumor, Node Node and and Metastasis Metastasis ( (TNM)TNM) classificationclassification,, and itit isis important,important among, among others, others to, to help help the the clinician clinician in thein the planning planning of treatment of treatment [8,9]. [8,9]The.T-staging The T-staging of eyelid of eyelid tumors tumors encompasses encompasses determination determination on whether on whether there there is an is invasionan invasion of the of theeyelid eyelid structures structures such such as the as tarsal the platetarsal andplate orbital and septumorbital septum [8,9], which [8,9] are, which not clinically are not accessibleclinically accessibleand, therefore, and, therefore imaging can, imaging be crucial can [be10 crucial] for an [10] accurate for an evaluation. accurate evaluation. To our knowledge, eyelid anatomy has never been described on CT, and only a few descriptions are available on MRI [2,11–18]. Similarly, we are not aware of any radiological study depicting which anatomic eyelid