Pathology of the Head and Neck

268 M. A Luna · K. Pineda-Daboin9praclavicular tumours) [15, 58]. There is no doubt thatmost, if not all of them are actually cervical node metastaseswith a cystic pattern. The palatine tonsil, or moregenerally the anatomic region of Waldeyer’s ring, is notoriousfor producing cystic solitary metastases that resemblethe usual appearance of branchial cleft cysts [69,73, 96, 116].All of the suspected branchiogenic carcinomas havebeen squamous-cell in type, and all but one have beenin the region of the second branchial apparatus [15, 58,86]. The patients have been predominantly males rangingin age from 38 to 71 years [15, 58]. Nearly all of thesemasses have been cystic and have resided in a lymphoidmatrix, hence the presumed relationship to a branchialcyst. It should be obvious that neither cystic architecturenor association with lymphoid tissue is, in itself, an acceptablecriterion for diagnosis of branchiogenic carcinoma[73, 96, 116].An absence or presence or peripheral lymphatic sinusesand/or follicular centres in the lymphoid tissuehas been used to exclude or confirm metastasis to thelymph nodes. This criterion is not valid. Branchial cleftcysts often lie within lymph nodes, and metastases canobscure the architecture of a lymph node [96, 116].9.3.3 Thyroglossal Duct Cystand Ectopic ThyroidCysts and sinuses may be found along the course of thethyroglossal duct; these cysts develop during the migrationof the thyroid gland from the base of the tongue.The cysts are situated in the midline of the neck, usuallybelow the hyoid bone. A fistula may develop froman infected cyst.The thyroid begins to develop during the 4th weekof gestation when the embryo is about 2–2.5 mm long[126]. It is an endodermal derivative composed of twosmall lateral anlagen and the more substantial mediananlage from the foramen caecum at the base ofthe tongue. Because of elongated cephalad embryonicgrowth rather than active descent, the orthotopic pretracheallocation of the thyroid is caudal to the foramencaecum [126].Thyroglossal duct cysts (TDC) are twice as commonas branchial cleft cysts. In a review of 1,534 cases in theliterature, Allard observed that, at the time of presentation,67% of patients had a cyst and 33% a fistula [5].Approximately 90% of TDC occur in the midline ofthe neck, although some may occur paramedially, mostoften on the left. Overall, 73.8% occur below the hyoidbone, 24.1% are suprahyoid, and 2.1% are intralingual[65]. Spinelli et al. reviewed their experience with neckmasses in children and noted that 17 (26%) of 154 caseswere TDC, and branchial cleft cysts were less common[115].Most patients with a TDC have no symptoms; theyseek evaluation for a midline neck mass discovered incidentallyby themselves or a family member. The mostcommon manifestations are pain, a draining sinus orfistula, infection, or dysphagia. A cyst in the floor ofthe mouth may cause feeding problems in newborns,whereas a cyst at the base of the tongue has, in rare instances,been responsible for sudden death in infancy[106].Thyroglossal duct cysts range in size from 0.5 to4 cm in diameter. They can be either unilocular or multilocularand usually contain mucoid material if the cystis not infected or mucopurulent material or pus if it is.The type of epithelium lining the cyst varies from onecase to another, or even within the same surgical specimen.A columnar to stratified cuboidal epithelium withcilia is the most common type of epithelial lining, foundin 50–60% of cases (Fig. 9.6). Lymphoid nodules in thewall of the cyst are found in 15–20% of cases, while theyoccur in 75% of branchial cleft cysts. A TDC with squamouslining and lymphoid tissue may be difficult to differentiatefrom a branchial cleft cyst. Immunoperoxidasestaining for thyroglobulin may be of help. Ectopicthyroid tissue is identified (as collections of thyroid folliclesin the soft tissues adjacent to the cyst) in 3 –20%of TDCs, although these figures are related to some extentto the number of tissue slides taken for histologicexamination and the extent of inflammatory and reactivechanges present in the surrounding tissue.Mucous glands were identified in 60% of the TDCstudied by Sade and Rosen [102]. These authors believethe mucous glands to be part of the normal thyroglossalapparatus and not just glands found at the base ofthe tongue.Thyroglossal duct remnants are treated by completesurgical excision using the Sistrunk operation [112].This consists of a block excision of the entire thyroglossaltract to the foramen caecum, as well as removal ofthe central 1–2 cm of the hyoid bone. If this procedure isperformed, the TDC recurrence rate is less than 5% [91].If the central portion of the bone is not removed, the recurrencerate is as high as 50% [3, 74].Ectopic thyroid is defined by identification of gross ormicroscopic thyroid tissue outside of the thyroid gland.Most commonly from the base of the tongue (lingualthyroid) to the mid-lower neck superior to the orthotopicthyroid [25]. The ectopia can be complete or more oftenassociated with an orthotopic thyroid.Hypothyroidism is a frequent finding in patients withlingual thyroid [105]. Batsakis and collaborators noted aclinical prevalence of lingual thyroid of 1 in 10,000 individuals,but an autopsy prevalence of 1 in 10 [10]. Ectopicthyroid is histologically composed of uniform, oftensmall, follicles containing minimal colloid. The microfolliclesare usually intercepted by the skeletal muscleof the tongue.