MEDizzy - A 14-month-old male infant presents with an enlarging

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General Pathology (III)

A 14-month-old male infant presents with an enlarging abdominal mass. Laboratory examination reveals increased urinary levels of metanephrine and vanillylmandelic acid (VMA). A histologic section from the mass reveals a tumor composed of small, primitive-appearing cells with hyperchromatic nuclei and little to no cytoplasm. Occasional focal groups of tumor cells are arranged in a ring around a central space. Which of the following is the most likely diagnosis?

ExplanationNeuroblastomas are malignant tumors of the adrenal medulla that occur in very young patients who present with an abdominal mass. Histologically, these tumors are composed of small cells forming Homer-Wright rosettes, which are groups of cells arranged in a ring around a central mass of pink neural filaments. Electron microscopy reveals neurosecretory granules within the cytoplasm of the tumor cells, while immunohistochemical stains are positive for neuron-specific enolase (NSE). These highly aggressive tumors are unique because some spontaneously regress and some dedifferentiate into benign tumors, such as ganglioneuromas. Three distinct chromosomal abnormalities are associated with neuroblastomas. These abnormalities include nearterminal deletion of part of the short arm of chromosome 1 (partial monosomy 1), homogeneously staining regions (HSRs) of chromosome 2, and multiple double minute chromatin bodies. The latter two are the result of amplification of the oncogene N-myc. The number of N-myc copies correlates with the aggressiveness of the tumor. Dedifferentiation of a neuroblastoma into a benign ganglioneuroma is associated with a marked reduction in this gene amplification.