Parathyroid gland
Miscellaneous
Pathologic TNM staging of parathyroid gland, AJCC 8th edition


Topic Completed: 9 April 2019

Revised: 9 April 2019

Copyright: 2019, PathologyOutlines.com, Inc.

PubMed Search: Parathyroid gland staging

Andrey Bychkov, M.D., Ph.D.
Page views in 2019 to date: 108
Cite this page: Bychkov A. Pathologic TNM staging of parathyroid gland, AJCC 8th edition. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/parathyroidstaging.html. Accessed August 21st, 2019.
Definition / general
  • Applicable to parathyroid carcinoma
  • First introduced in AJCC 8th edition
  • There is limited evidence on significant prognostic factors in parathyroid carcinoma
  • Prognostic significance of tumor size, extent of invasion or regional lymph node involvement is unclear and studies are conflicting
  • Presence of distant metastasis is the only consistent factor across the literature that is predictive of overall survival
  • While TNM definitions have been established, no universal staging system is available so far; instead, AJCC / TNM includes recommendations for recording data collection variables in the cancer registry to be used to develop a formal staging system in the future
  • Microscopic and macroscopic classifications of the primary tumor have not been standardized
Essential features
  • T, N and M categories are established but no cancer stages defined at the moment
  • Distant metastasis (M category) is the major predictor of overall survival
ICD coding
  • ICD-10: C75.0 - Parathyroid gland
Primary tumor (pT)
  • pTX: primary tumor cannot be assessed
  • pT0: no evidence of primary tumor
  • pTis: atypical parathyroid neoplasm (neoplasm of uncertain malignant potential) (see notes below)
  • pT1: localized to the parathyroid gland with extension limited to soft tissue
  • pT2: direct invasion into the thyroid gland
  • pT3: direct invasion into recurrent laryngeal nerve, esophagus, trachea, skeletal muscle, adjacent lymph nodes or thymus
  • pT4: direct invasion into major blood vessel or spine

Notes:
  • Atypical parathyroid neoplasm is defined as a tumor that is histologically or clinically worrisome but does not fulfill the more robust criteria (i.e. invasion, metastasis) for carcinoma
    • Generally includes tumors that have 2 or more concerning features, such as fibrous bands, mitotic figures, necrosis, trabecular growth or adherence to surrounding tissues intraoperatively
    • Usually have a smaller dimension, weight and volume than carcinomas and are less likely to have coagulative tumor necrosis
Regional lymph nodes (pN)
  • pNX: regional lymph nodes cannot be assessed
  • pN0: no regional lymph node metastasis
  • pN1: regional lymph node metastasis
    • pN1a: metastasis to level VI (pretracheal, paratracheal and prelaryngeal / Delphian lymph nodes) or superior mediastinal lymph nodes (level VII)
    • pN1b: metastasis to unilateral, bilateral or contralateral cervical (level I, II, III, IV or V) or retropharyngeal nodes
Distant metastasis (pM)
  • pM0: no distant metastasis
  • pM1: distant metastasis
AJCC prognostic stage groups
  • Not established in the current AJCC / TNM
Registry data collection variables
  • Age at diagnosis
  • Gender
  • Race
  • Size of primary tumor in millimeters
  • Location of primary tumor: left or right and superior (upper) or inferior (lower)
  • Invasion into surrounding tissue (present or absent)
  • Distant metastasis
  • Number of lymph nodes removed (by level)
  • Number of lymph nodes positive (by level)
  • Highest preoperative calcium (mg/dL)
  • Highest preoperative parathyroid hormone (pg/mL)
  • Lymphovascular invasion (present or absent)
  • Grade (low or high)
  • Weight of primary tumor (in milligrams)
  • Mitotic rate
  • Time to recurrence (months)
Histologic grade
  • Low grade: round monomorphic nuclei with only mild to moderate nuclear size variation, indistinct nucleoli and chromatin characteristics resembling those of normal parathyroid or of adenoma
  • High grade: more pleomorphism, with a nuclear size variation > 4:1; prominent nuclear membrane irregularities; chromatin alterations, including hyperchromasia or margination of chromatin; and prominent nucleoli; high grade tumors show several discrete confluent areas with nuclear changes
Histopathologic type
Board review question #1
A patient presented with a parathyroid carcinoma directly invading thyroid and adjacent fibroadipose tissue. What is the pT category?

  1. pTis
  2. pT1
  3. pT2
  4. pT3
  5. pT4
Board review answer #1
Board review question #2
A 72 year old man presented with a 4 cm advanced parathyroid carcinoma invading trachea and thyroid and showing cervical lymph nodes metastasis along with dissemination in the lungs. What is the clinical stage as per the AJCC / TNM 8th edition?

  1. Stage I
  2. Stage II
  3. Stage III
  4. Stage IV
  5. Not applicable
Board review answer #2
E. Not applicable; no AJCC / TNM staging system for parathyroid carcinoma is available so far, only standalone TNM categories

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