This presentation from Grossing Rounds focuses on the anatomical handling, orientation, and pathological gross examination of thyroidectomy specimens, specifically utilizing a right hemithyroidectomy case. The session details proper inking protocols (green for anterior, black for posterior, orange for the isthmic margin) and reviews the four main types of thyroid cancer: Papillary, Follicular, Medullary, and Anaplastic, discussing their frequency, associated risk factors, and gross features (e.g., solid white nodule for Papillary). A critical component of the presentation is the procedural approach to grossing based on pre-operative Fine Needle Aspiration (FNA) results, guided by the Bethesda System. Emphasis is placed on specific sectioning strategies, such as submitting the entire capsule for follicular lesions to distinguish adenoma from carcinoma. Finally, the presentation covers the T (tumor size and extension) and N (regional lymph node metastasis) staging criteria for thyroid cancer, concluding with an overview of standard radical neck dissection components.
Grossing Rounds: Hemithyroidectomy and Thyroid Carcinoma
0:10 Specimen Identification: The specimen is identified as a right hemithyroidectomy. The thyroid gland is a butterfly-shaped endocrine organ (normal adult weight 15–20g) consisting of right and left lobes connected by the Isthmus, sometimes including a pyramidal lobe.
0:11 Thyroid Function: The thyroid releases T3 and T4 hormones, regulating metabolism, heart rate, energy levels, and growth of skin, hair, and nails.
2:54 Orientation Techniques: Orientation relies on anatomical features: the anterior surface is typically convex and smooth, while the posterior surface is concave and rough (due to fibrous adhesions). Superior poles are pointed; inferior poles are rounded (though pathology can distort this). The isthmic resection margin appears cauterized or pinched off.
4:41 Reasons for Thyroidectomy: Procedures are performed for multi-nodular goiters, Graves disease, prophylactic measures (e.g., familial medullary carcinoma history), and benign or malignant nodules.
5:50 Specimen Inking Protocol: Standardized institution inking is presented: Black for the posterior surface, Green for the anterior surface, and Orange for the isthmic resection margin (applied only to the margin itself, not the Isthmus tissue).
6:51 Four Main Types of Thyroid Cancer (Most to Least Common):
Papillary (PTC): Most common (85%). Grossly appears as solid, white nodules with irregular borders (7:43). Associated with significant ionizing radiation exposure.
Follicular: Accounts for 6–10%. Grossly tan or brown, single, encapsulated nodules. Differentiation from follicular adenoma is critical, relying entirely on the identification of capsular or vascular invasion (10:37).
Medullary: 1–2% of cases, derived from C cells (neuroendocrine tumor). Associated with MEN 2A and 2B syndromes. Grossly firm, gray, tan, or yellow.
Anaplastic: Least common (1%). Highly aggressive, rapidly enlarging, and often invades adjacent structures. Mean one-year survival is 10–20%.
15:40 Pre-Grossing Necessity (FNA): Reviewing the Fine Needle Aspiration (FNA) results, reported using the six-tiered Bethesda System, is crucial as the results (e.g., suspicious vs. benign) dictate the required number of sections submitted.
19:40 Sectioning Protocols (Hemithyroidectomy): Thyroid tissue is serially sectioned superior to inferior in the transverse plane (0.3 cm thickness), keeping the specimen hinged. Poles are sectioned parasagittally. The isthmic resection margin is submitted perpendicularly (not en face).
24:04 Sectioning Follicular Cases (Key Takeaway): For follicular carcinoma, the entire capsule of the nodule must be submitted, including margins and interface with normal parenchyma, to microscopically assess for invasion.
T2: $>2$ cm to $\le 4$ cm, limited to the thyroid.
T3b (Critical Point): Any size tumor extending into the strap muscles (sternohyoid, sternothyroid, thyrohyoid, omohyoid).
T4 (a/b): Gross extension into major structures (larynx, trachea, esophagus, carotid artery).
30:35 N Staging and Delphian Node: The Delphian lymph node (pre-laryngeal node) is located in Level 6 (the central compartment) and is often the first site of metastasis (N1a).
33:44 Radical Neck Dissections (RND): A standard RND includes cervical lymph node levels 1 through 5, the SCM muscle, internal jugular vein, and spinal accessory nerve. Central compartment lymph nodes (Level 6) are explicitly NOT included in a standard RND.
39:48 Metastasis Patterns (Key Takeaway): Unlike Papillary cancer which typically spreads through lymphatics, Follicular thyroid carcinoma is known to spread via blood vessels (hematogenously), most commonly metastasizing to the lung and bone.