1. CD5

2. CD56

3. IHC
CK:POSITIVE NSE:POSITIVE EMA:POSITIVE CHROMOGRANIN:POSITIVE S100:NEGATIVE SYNAPTOPHISIN:POSITIVE
CD56:POSITIVE KI67:POSITIVE IN 10% OF NUCLEI CD5:NEGATIVE

4. DIFFERENTIAL DIAGNOSIS
-Carcinoid tumor -Thymic carcinoma -Neuroendocrine carcinoma -Type A thymoma -Paraganglioma

5. CARCINIOD TUMOR
-Malignant neoplasm that often invades locally and metastasizes distantly -usually lacks endocrine manifestation -component of MEN type1 , NF1 -more aggressive neoplasm than bronchial carcinoid,,,fall into the category of atypical carcinoid tumor

6. CARCINOID TUMOR
Grossly, thymic carcinoid is solid, usually well circumscribed but not encapsulated, and lacks the distinct lobulations of thymoma. It tends to be highly vascularized and may be'frankly
hemorrhagic.-

7. Microscopically, thymic carcinoid tumor exhibits ribbon and festoon formation, rosette-like glands with central lumina, 'balls' of cells with central necrosis and calcification, marked vascularization and frequent lymphatic and blood vessel invasion. Lymphocytes, perivascular spaces, and other features of thymoma are absent. The tumor cells have a more granular cytoplasm than those of thymoma, the nuclear chromatin is slightly coarser, and mitotic activity is frequent.

8. Carcinoid tumor . Ribbons and rosettes
Central necrosis with calcification

9. IHC
lmmunohistochemically,there is reactivity for keratin, chromogranin, synaptophysin, neuronspecific enolase, and other general endocrine markers. In addition,the tumors associated with Cushing syndrome show positivity for adrenocorticotropic hormone (ACTH). Other substances detected in this tumor include serotonin, somatostatin, cholecystokinin,neurotensin. and metenkephalin

10. Neuroendocrine carcinoma
Smal cell n.e.c
Large cell n.e.c
- indistinguishable from that of its pulmonary counterpart
-a mediastinal metastasis of a pulmonary neoplasm has been ruled out.
- There are also cases combining features of carcinoid tumor and small cell carcinoma in the same lesion
higher number of mitoses (over 10 per 10 HPF) and exhibit foci of necrosis, often extensive. In general, their neuroendocrine architecture is not nearly as well developed. It is manifested - at most - by nesting with peripheral palisading and some rosette-like structures.

11. NOT ALL MEDIASTINAL NEUROENDOCRINE CARCINOMAS ARE FROM THYMIC ORIGIN
NOT ALL THYMIC TUMORS WITH NEURAL DIFFERENTIATION ARE NEUROENDOCRINE CARCINOMA
NOT ALL MEDIASTINAL NEUROENDOCRINE CARCINOMAS ARE FROM THYMIC ORIGIN

12. IHC OF THYMIC CARCINOMA
1-CD5 POSITIVE 2-CD117 POSITIVE 80-86% 3-CD70 POSITIVE 4-TTF1 NEGATIVE 5-P53 and BCL2 stronger than thymomas 6-focal neuroendocrine differentiation

14. Well circumscribed tumors are often cured by
local excision
Thymic carcinoid is a more aggressive neoplasm than bronchial carcinoid

15. sternberg

18. Immunohistochemically, TCTs are regularly reactive for keratin,
neuron-specific ()'-dimeric) enolase, synaptophysin, CD56,
CD57, and chromogranin A

19. Immunohistochemically, the nonepithelial nature of paragangliomas is reflected in their consistent negativity for keratin and EMA. Instead, these neoplasms express neurofilament protein or vimentin (410). The S-100 protein immunostain may
be employed to decorate fusiform "sustentacular" cells that surround cellular nests in paragangliomas (442), and the tumor cells themselves often contain one ofthe enkephalin neuropeptides