Workup/Staging Flashcards
What is the DDx of a mediastinal mass by location in the ant, middle, and post ME?
Ant: Thymoma, thymic carcinoma, thyroid (retrosternal), germ cell tumors, lymphomas, carcinoid, T aorta (Mnemonic: TTTT: Thymoma, Teratoma, Thyroid neoplasm, Terrible lymphoma)
Middle: Cysts > lymphoma, teratomas > sarcomas (osteosarcoma, fibrosarcoma, angiosarcoma, rhabdomyosarcoma of the heart), granuloma
Post: Neurogenic tumors (PNET, schwannoma, neurofibroma, NB, ganglioneuroma), pheochromocytoma
What clinical presentations are common for pts with mediastinal tumors?
About one-half are diagnosed incidentally on imaging studies. The remainder present with local Sx (cough, shortness of breath, pain, stridor, phrenic nerve palsy, Horner syndrome, SVC syndrome) or as an association with MG if thymoma.
What are some key features that help to distinguish a lymphoma, teratoma, and germ cell tumors?
Lymphomas can be associated with B Sx (fever >38°C, drenching night sweats, weight loss >10% in preceding 6 mos), elevated LDH, and LA. Teratomas tend to have a heterogeneous imaging appearance with a fat and cystic component. Germ cell tumors are associated with an elevated a-HCG, AFP and have a sudden onset.
How do pts with thymomas or thymic carcinomas usually present?
50% are incidental findings. If there are Sx, they reflect either locally advanced Dz, metastatic sequelae, or paraneoplastic disorders (in 50%–60% of thymomas but hardly seen in thymic carcinomas).
What paraneoplastic disorders are commonly seen in thymomas?
MG (35%–50% of cases), pure red cell aplasia (5%–15%), immune deficiency syndromes such as hypogammaglobulinemia (5%–10%), autoimmune disorders (collagen vascular, dermatologic, endocrine, renal Dz), and other malignancies (lymphomas, GI/breast carcinomas, Kaposi sarcoma).
What workup should be employed for a mediastinal mass?
Mediastinal mass workup: H&P (ask about B Sx, MG Sx, physical to assess nodal and neurologic status). Basic labs (CBC and reticulocyte count to r/o red cell aplasia, TFTs to r/o thyroid Dz, AFP/a-HCG to r/o germ cell tumor, LDH and ESR to r/o lymphoma, and antiacetylcholine receptor and antinuclear antibodies). PFTs to assess lung function. Imaging (PA/Lat CXR, CT or MRI chest, PET if lymphoma suspected but has limited role in detecting thymic malignancy). Bx (FNA, but preferably Tru-Cut core Bx or incisional surgical Bx via video-assisted thoracoscopic Sg, Chamberlain procedure).
Is an MRI sup to CT imaging of the chest for ant mediastinal masses?
No. Aside from cystic lesions, CT is equivalent, or even sup in some settings, to MRI for Dx of ant mediastinal masses. (Seki et al., Eur J Radiol 2014)
The Dx of thymoma is essentially established clinically if the pt presents in what way?
Ant mediastinal mass with Sx of MG, red cell aplasia, or hypogammaglobulinemia
Appx what % of pts with thymoma present with MG?
35%–50%. Conversely, 10%–15% of pts with MG have thymoma.
What are the pathogenesis, presentation, Dx, and Tx of MG?
Autoantibody to the acetylcholine receptor at the postsynaptic endplate. Pts present with easy fatigability of skeletal muscles (with preserved sensation, reflexes), dysphagia, ptosis, and diplopia. Sx worse with movement, whereas the opposite is true for Lambert–Eaton. Dx is by the Tensilon test (edrophonium). Tx is by anticholinesterase (pyridostigmine) or thymectomy (reverses in 40% of pts with thymoma).
What is the Modified Masaoka system used to stage thymomas?
Stage I: fully encapsulated, no microscopic capsular invasion
Stage IIA: microscopic invasion into capsule
Stage IIB: macroscopic invasion into surrounding fat or mediastinal pleura
Stage III: macroscopic extension to surrounding organs (lung, pericardium), without great vessel invasion (A) or with great vessel invasion (B)
Stage IVA: pleural or pericardial dissemination.
Stage IVB: +LN or DM
Is there controversy regarding the Masaoka staging system for thymoma?
Yes. UCLA retrospective meta-analysis of ∼2,500 pts showed no difference in DFS or OS b/t stages I and II pts. (Gupta R, Arch Pathol Lab Med 2008)
What are the 5-yr survival rates for thymomas based on the Masaoka staging?
5-yr survival for thymomas (Masaoka staging):
Stage I: 95%
Stage II: 90%
Stage III: 60%
Stage IV: 11%–50%
Based on modern surgical series, what are the rates of complete resection, the recurrence rate, and 5-yr OS based on Masaoka staging?
Based on outcomes for 1,320 pts. The % of complete resection, % of recurrence, and 5-yr OS, respectively, were as follows (Kondo et al., Ann Thorac Surg 2003):
Stage I: 100%, 1%, 100%
Stage II: 100%, 4%, 98%
Stage III: 85%, 28%, 89%
Stage IVA: 42%, 34%, 71%
According to AJCC 8th edition, is there a difference b/t encapsulated and unencapsulated thymoma?
No. Encapsulation does not appear to be clinically relevant. The capsule appears to be generated by a tumor-related process and not actually an anatomic structure of the thymus. This is a difference compared to the Masaoka staging system.
