Head and Neck Flashcards
What are the key diagnostic features required for diagnosis of poorly differentiated thyroid carcinoma?
The primary required features are: 1) high mitoses (>3/10 HPF) and 2) necrosis
Often, there is a high N:C ratio, and insular growth, but not absolutely required
How do you distinguish the cribriform pattern of PLGA from adenoid cystic carcinoma?
IN PLGA, the nuclei have delicate and even chromatin, while in ACC, there are course, hyperchromatic nuclei, often with peg-shapes
Also slate -blue gray stroma is characteristic of PLGA and absent in ACC
Finally by IHC, in ACC the luminal cells will be CK-7 positive, CKit positive. While the more myoepithelial population will be S100, CK5/6, or S100 positive.
Describe the IHC profile of Olfactory Neuroblastoma (ONB) and how it overlaps with important differentials
ONB is positive for the neuroendocrine markers synaptophysin, chromogranin, and CD56 while S100 protein highlights the sustentacular supporting cells at the periphery of the tumor nests. Occasionally, ONB may exhibit unusual forms of differentiation that may obscure the diagnosis. Most common is epithelial differentiation, but rarely, ONB may exhibit melanocytic or rhabdomyoblastic differentiation.
It is important to distinguish ONB with rhabdomyoblastic differentiation from RMS, a problem compounded by both tumors being encountered in the sinonasal tract of young patients. Additionally, the alveolar subtype of RMS may express neuroendocrine markers, with nearly universal CD56 expression. An important key to this dilemma is recognizing the nature of the myogenin expression. Alveolar RMS, a nested, small round cell tumor, generally demonstrates diffuse myogenin expression, in contrast to the patchy distribution seen in ONB. Moreover, even in the face of patchy rhabdomyoblastic differentiation, classic areas of ONB should be recognizable in the background. Finally, in a very difficult case, molecular studies for the t(2;13) or t(1;13) translocations of alveolar RMS may be useful.
