Clinical Pathology: Urinalysis, Body Fluids, Clinical Microscopy

551) This cerebrospinal fluid (CSF) specimen in the figure was obtained by lumbar puncture from a 5-year-old boy. The findings are most consistent with which one of the following diagnoses?

• Microscopic Description: Two atypical clusters of cells in a background of red blood cells. The medulloblastoma cells are large relative to the red blood cells. In addition, they have irregular nuclear contours and demonstrate nuclear molding—a feature that distinguishes them from lymphoid cells.

• Normal cerebrospinal fluid (CSF) has rare cells.

• Small round blue cell tumors include lymphoma/leukemia, small cell carcinoma, and medulloblastoma.

• Nuclear molding may be present in medulloblastoma and small cell carcinoma.

• Small cell carcinoma lacks nucleoli.

• Small cell carcinoma is more likely to be seen in adults, whereas medulloblastoma affects children.

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