Z028

 

Synchronous papillary (pT1a(m)N0) and medullary (pTxN1b) thyroid cancer a diagnostic pitfall

 

A Hellmann, Department of General, Endocrine and Transplant Surgery Medical University of Gdańsk, Poland

 

 

A 34-year-old male with a neck pain and left side submandibular lymphadenopathy admitted to otorhinolaryngology (ORL) outpatient clinic. Fine needle aspiration biopsy (FNAB) of enlarged lymph node was made. With the initial diagnosis of malignant salivary gland neoplasm were sent for magnetic resonance (MRI) (Figure 1A) which revealed pathological lymph nodes with no abnormalities in salivary glands. Additionally, PET with 18F-FDG was done (Figure 1B) - it showed active metabolic process in several lymph nodes of the upper and middle part of the neck. Subsequently, bilateral tonsils, pharyngeal lymphatic tissue and enlarged left side (II group) lymph node were removed. Histopathological examination of the specimens demonstrated macro metastasis of medullary thyroid carcinoma (MTC) to the lymph node with positive staining of synaptophysin, chromogranin A, calcitonin and Ki 67- 7%. Pheochromocytoma was ruled out. Serum calcitonin level was 300 ng/ml. After interdisciplinary decision, radical thyroidectomy with bilateral and central lymphadenectomy was performed. Specimen was evaluated independently by two experienced histopathologists, the result was: multifocal papillary thyroid cancer in the thyroid gland (pT1a(m)N0) and left sides lymph nodes (group II-IV) 7/29 and central (group VI) 2/4 positive for MTC metastases; but surprisingly primary MTC tumor was not found (pTxN1b) (Figure 1C). The post-operative period was uneventful. On subsequent follow-up visit RET and BRAF mutation were excluded, the patient was doing well. Calcitonin level in 6-month observation is below 2 pg/ml.

 

The simultaneous occurrence of MTC and PTC is a very rare phenomenon. It usually observed in two main settings: a mixed tumor (dual differentiation) or a collision tumor (with two separate and different components) [1]. The current cases belong to even different category with two independent malignancies with unknown primary site of one of them.