CT CT Fine Needle Aspiration Cytology 3 — Questions and Answers
Question 1: FNA of a soft tissue mass yields spindle cells with cigar-shaped nuclei, no necrosis, and a fascicular arrangement in a 25-year-old. Which diagnosis should be considered first?
- Rhabdomyosarcoma
- Nodular fasciitis or benign spindle cell lesion (Correct answer)
- Leiomyosarcoma
- Synovial sarcoma
Correct answer: Nodular fasciitis or benign spindle cell lesion
In a young patient, a benign lesion like nodular fasciitis is the most common cause of a rapidly growing spindle cell soft tissue mass and should be excluded before considering sarcoma.
Question 2: Which immunohistochemical marker pair is most useful to differentiate mesothelioma from adenocarcinoma on cell block material from a pleural fluid or FNA?
- CK7 and CK20
- Calretinin/WT-1 (positive in mesothelioma) vs TTF-1/CEA (positive in adenocarcinoma) (Correct answer)
- S100 and HMB-45
- Synaptophysin and chromogranin
Correct answer: Calretinin/WT-1 (positive in mesothelioma) vs TTF-1/CEA (positive in adenocarcinoma)
Mesothelioma expresses mesothelial markers (calretinin, WT-1, D2-40) while adenocarcinoma expresses epithelial markers (TTF-1 for lung, CEA, MOC-31), enabling reliable differentiation.
Question 3: In FNA cytology of the liver, which cytomorphologic finding is most specific for hepatocellular carcinoma (HCC) compared to metastatic adenocarcinoma?
- Intracytoplasmic bile pigment and transgressing endothelial cells (sinusoidal capillaries within tumor fragments) (Correct answer)
- Mucin vacuoles and nuclear palisading
- Single atypical cells with high N:C ratio
- Psammoma bodies
Correct answer: Intracytoplasmic bile pigment and transgressing endothelial cells (sinusoidal capillaries within tumor fragments)
HCC characteristically shows intracytoplasmic bile, bile canaliculi between cells, and thin-walled capillaries traversing tumor cell groups (endothelial wrapping), features absent in metastatic carcinoma.
Question 4: FNA of a kidney mass in a 50-year-old yields cells with abundant clear cytoplasm, small round nuclei with inconspicuous nucleoli, and rich vascularity. What is the most likely diagnosis?
- Oncocytoma
- Clear cell renal cell carcinoma (Correct answer)
- Urothelial carcinoma
- Angiomyolipoma
Correct answer: Clear cell renal cell carcinoma
Clear cell RCC is characterized by cells with optically clear or finely vacuolated cytoplasm (due to glycogen/lipid), low-grade nuclei, and a prominent arborizing vasculature in aspirates.
Question 5: Which adequacy criterion applies to FNA of a cystic thyroid nodule that yields only macrophages and no follicular cells?
- Always unsatisfactory
- Satisfactory if the nodule was entirely aspirated and cyst fluid examined (Correct answer)
- Requires immediate repeat FNA
- Satisfactory only if the nodule resolved after aspiration
Correct answer: Satisfactory if the nodule was entirely aspirated and cyst fluid examined
A cyst that has been completely aspirated and yields only macrophage-rich fluid without follicular cells is a recognized exception to the 6-group rule and can be reported as satisfactory.
Question 6: Which cytologic feature best distinguishes Hürthle cell neoplasm from Hashimoto thyroiditis on thyroid FNA?
- Granular eosinophilic cytoplasm
- Absence of lymphocytes and plasma cells; presence of pure Hürthle cell population without normal follicular cells (Correct answer)
- Large cell size
- Prominent nucleoli
Correct answer: Absence of lymphocytes and plasma cells; presence of pure Hürthle cell population without normal follicular cells
Hürthle cell neoplasm yields a pure population of oncocytic cells without background lymphocytes, while Hashimoto thyroiditis contains Hürthle cells admixed with abundant lymphocytes and plasma cells.
CT CT Fine Needle Aspiration Cytology 3
FNA of a soft tissue mass yields spindle cells with cigar-shaped nuclei, no necrosis, and a fascicular arrangement in a 25-year-old.
Which diagnosis should be considered first?