Medulloblastoma with excessive nodularity: radiographic features and pathologic correlate

Abstract

Medulloblastoma with extensive nodularity is a rare subtype of the most common malignant childhood brain tumor and has been associated with more favorable prognosis. The authors report the case of a 10-month-old girl with a posterior fossa tumor of excessive nodularity with decreased diffusivity on diffusion-weighted magnetic resonance imaging sequences and robust grape-like postgadolinium contrast enhancing features. The unique neuroradiographic features were confirmed by histopathology and a diagnosis of medulloblastoma with extensive nodularity was made. This case highlights the importance of recognizing this unique medulloblastoma subtype preoperatively, as the more favorable outcome may preclude less aggressive medical management.

Figure 1

MRI features of medulloblastoma with extensive nodularity: (a)–(c) axial sequences reveal a posterior fossa mass (arrows) with decreased diffusivity on DWI (a) and ADC sequences (b), without specific intratumoral abnormalities on SWI sequence aside from amorphous susceptibility artifact present along the vermis from prior surgical biopsy (c). Sagittal sequences reveal extensive nodularity on T2 (d) and postgadolinium (f) sequences that is less evidence on precontrast T1-weighted sequences where the nodular areas appear more hypointense (e).

Figure 2

Histologic features of medulloblastoma with extensive nodularity. Hematoxilin and eosin section (4 μm; 100x) reveals a malignant small blue cell tumor with widespread formation of nodules of uniform cells with neuropil formation surrounded by intervening areas of more densely populated pleomorphic cells consistent with a diagnosis of medulloblastoma with extensive nodularity. The arrowheads point to the nodular zones.