1. Differential diagnosis of Neck masses A mass in the neck is a common finding that present in patients of all age groups. The differential diagnosis may be extremely wide. There are 3 main categories: inflammatory, congenital and neoplastic which are different in their distribution according to the age. The congenital and inflammatory masses are more common in children and adults below 40 years while a mass in an adult above 40 should be considered as neoplastic until proved otherwise.

2. Surgical anatomy It is impossible to understand the assessment, diagnosis or detailed surgical treatment of any procedure within the neck without understanding the underlying anatomy. Anatomical divisions: The neck is divided by the sternomastoid muscle into 2 triangles: anterior and posterior. The posterior t. is bounded by the trapezius m. posteriorly, middle third of the clavicle inferiorly and posterior border of the sternomastoid m. anteriorly. It can be further subdivided by the omohyoid m. into superior occipital t. and lower subclavian t. The anterior t. is bounded by the anterior border of sternomastoid m. posteriorly, mandible superiorly and the midline of the neck anteriorly. It can be further subdivided into 4 smaller triangles: muscular, carotid, submandibular and submental triangles. The structures lying deep to the sternomastoid m. are considered within the anterior triangle.

3. Fascial neck spaces Understanding fascial neck layers and spaces is crucial since operative procedures appear easier, less vascular and are better controlled if they proceed along fascial spaces rather than through them. The superficial fascia of the neck is a single layer of fibrofatty tissue lying superficial to the platysma muscle. The deep cervical fascia is more extensive and much more important and lies deep to the platysma m. There are 3 layers of the deep cervical fascia: 1- investing layer: invests the whole neck and splits to surround the trapezius m. posteriorly and sternomastoid anteriorly. It also surrounds the parotid and submandibular glands and forms the carotid sheath which surrounds both external and internal carotid arteries, the common carotid artery along with the internal jugular vein and the vagus nerve. This layer forms the roof of the anterior and posterior triangles. 2- visceral or middle layer: surrounds the pharynx, larynx, esophagus and trachea and allow these structures to slide upon each others. The pretracheal fascia which surround the thyroid gland is included in this layer. 3- internal layer: also known prevertebral fascia and surrounds the deep muscles of the neck i.e. the 3 scalenus mm., longus capitus and logus colli, erector spinae and levator scapula m. It forms the floor of the posterior triangle and has important relations with some important nerves in the neck. The cervical sympathetic trunk lies superficial to prevertebral f. while the phrenic nerve and brachial plexus lie deep to it.

4. Head and Neck lymphatics There are more than 500 LN in the body, about 200 found in the neck. The lymphatic drainage of the head and neck is divided into superficial and deep systems. The superficial system which drains the superficial tissues of the head and neck consists of 2 circles one in the head and the other is in the neck. In the head the lymph nodes are situated around the skull base and known as the occipital, postauricular, parotid and buccal LN. In the neck are the superficial cervical, anterior jugular, submandibular and submental LN. The superficial system receive s drainage from the skin and underlying tissues of the scalp and face.

5. The deep system Consists of : 1- junctional LN : along the internal jugular vein and divided into upper, middle and lower groups. 2- spinal accessory group: accompany the spinal accessory nerve in the posterior triangle. 3- visceral nodes: in the midline of the neck and upper mediastinum. The deeper structures of the head and neck drain either directly into the deep system or indirectly through the superficial system first then into the deep system.

6. It is convenient to use the level system to describe the location of LNs in the neck. Level 1: submental and submandibular LN. Level 2: upper jugular LN. Level 3: middle jugular LN. Level 4: lower jugular LN. Level 5: posterior triangle LNs ( occipital and spinal accessory LNs). Level 6: anterior midline LNs : pretracheal, prelaryngeal and precricoid LNs. Level 7: upper anterior mediastinal LNs.

7. Causes of a mass in the neck 1- Mass in the anterior triangle a- midline mass b- lateral mass 2- Mass in the posterior triangle

8. Mass in the anterior triangle A- Midline neck mass Congenital 1- Thyroglossal cyst: Remnant of the thyroglossal duct through which the thyroid gland descends from the foramen cecum in the tongue to its usual position in the neck. The duct atrophies but may persist as thyroglossal cyst. It usually lies in the midline of the neck closely related to the hyoid bone as painless, mobile, cystic mass and moves with swallowing and tongue protrusion. Treatment : surgical removal of the cyst with the midportion of the hyoid bone (Sistrunk procedure) to prevent recurrence. 2- Dermoid cyst: Is an epithelium-lined cavity filled with skin appendages (e.g., hair follicles and sebaceous glands), more common in the submental region in the neck but might be found in other sites in the head and neck as the nose and orbit.. It does not move on swallowing or tongue protrusion. Treatment: surgical excision.

9. Acquired 1- Ludwig's angina : Inflammation of the soft tissues of the floor of the mouth which may extends into the neck causing midline swelling in the submental region. Mostly due to dental problem and caused by Streptococcus viridans. The swelling is tender, hot and associated with fever and trismus. Treatment : broad spectrum antibiotics with oral hygiene. Incision and drainage rarely needed. 2- Perichondritis of thyroid cartilage: Usually follows radiation to the neck or neck trauma. Clinically: firm, tender swelling over the thyroid cartilage with bad odor. Pseudomonas is the commonest M.O. isolated Treatment: antibiotics with steroids. In resistant cases total laryngectomy is indicated. 3- Tumors of the larynx: Advanced malignant tumors of the larynx may invade the laryngeal cartilage and skin presenting as a midline neck mass. 4- Thyroid isthmus swelling: Whether simple, toxic or neoplastic. Presented as a solid or cystic mass and moves up with swallowing.

10. 5- Lymph node enlargement: lymphadenopathy (LAP) Submental, prelaryngeal, pretracheal or precricoid LNs. The cause is either inflammatory or neoplastic. 6- Skin and associated structures: A- Boil: Staph.aureus infection of the hair follicle. Present as a hot tender skin nodule Treatment: drainage with anti-staph. Antibiotics as cloxacillin. B- Sebaceous cyst : Due to obstruction of the sebaceous gland duct. Presented as a cystic painless mass with a characteristic punctum on its surface. Treatment : surgical excision. C- Lipoma: Slowly growing, ill-defined tumor of fat cells. It is non-tender and lobulated mass. Treatment: surgical excision if symptomatic. D- Skin tumors: Benign as keratoacanthoma and naevi. Or malignant as squamous cell carcinoma, basal cell carcinoma and melanoma.