The Neuroblastic Tumors

The term "neuroblastic tumor" includes tumors of the sympathetic ganglia and adrenal medulla that are derived from primordial neural crest cells populating these sites. As a family,

neuroblastic tumors demonstrate certain characteristic features such as spontaneous or therapy-induced differentiation of primitive neuroblasts into mature elements, spontaneous tumor

regression, and a wide range of clinical behavior and prognosis, which often mirror the extent of histologic differentiation. Neuroblastoma is the most important member of this family. It

is the second most common solid malignancy of childhood

after brain tumors, accounting for 7% to 10% of all pediatric neoplasms, and as many as 50% of malignancies diagnosed in infancy.[108] Approximately 650 new cases are diagnosed in the

United States each year, accounting for an incidence of approximately 9.5 cases per million children. The median age at diagnosis is 22 months; a little more than a third of the cases are

diagnosed in infancy. There is a higher incidence of neuroblastoma in Caucasian as compared to African American populations, and males are at a marginally greater risk than females.

Alone, it accounts for at least 15% of all childhood cancer deaths, although the 5-year survival rate has improved from 25% in the early 1960s to almost 55% in the mid-1990s. As will be

evident later, age and stage have a remarkable effect on prognosis, and, in general, infants tend to have a significantly better prognosis than older individuals. Most occur sporadically, but a

few are familial with autosomal dominant transmission, and in such cases the neoplasms may involve both of the adrenals or multiple primary autonomic sites.

Morophology.

In childhood, about 40% of neuroblastomas arise in the adrenal medulla. The remainder occur anywhere along the sympathetic chain, with the most common locations being the

paravertebral region of the abdomen (25%) and posterior mediastinum (15%). Tumors may arise in numerous other sites, including the pelvis and neck and within the brain (cerebral

neuroblastomas).

Macroscopically, neuroblastomas range in size from minute nodules (the in situ lesions) to large masses more than 1 kg in weight ( Fig. 10-27 ). In situ neuroblastomas are reported to be

40 times more frequent than overt tumors. The great majority of these silent lesions spontaneously regress, leaving only a focus of fibrosis or calcification in the adult. Some

neuroblastomas

Figure 10-27Adrenal neuroblastoma in a 6-month-old child. The hemorrhagic, partially encapsulated tumor has displaced the opened left kidney and is impinging on the aorta and left

renal artery. (Courtesy of Dr. Arthur Weinberg, University of Texas Southwestern Medical School, Dallas, TX.)

Figure 10-28Adrenal neuroblastoma. This tumor is composed of small cells embedded in a finely fibrillar matrix.

Figure 10-29Ganglioneuromas, arising from spontaneous or therapy-induced maturation of neuroblastomas, are characterized by clusters of large cells with vesicular nuclei and abundant

eosinophilic cytoplasm, representing neoplastic ganglion cells (arrow). Spindle-shaped Schwann cells are present in the background stroma.

Stage 2A:Localized tumor with incomplete gross resection. Representative ipsilateral nonadherent lymph nodes negative for tumor microscopically.

Stage 2B:Localized tumor with or without complete gross excision, ipsilateral nonadherent lymph nodes positive for tumor. Enlarged contralateral lymph nodes, which are

negative for tumor microscopically.

Stage 3:Unresectable unilateral tumor infiltrating across the midline with or without regional lymph node involvement; or localized unilateral tumor with contralateral regional

lymph node involvement.

Stage 4:Any primary tumor with dissemination to distant lymph nodes, bone, bone marrow, liver, skin, and/or other organs (except as defined for stage 4S).

Stage 4S("S" = special): Localized primary tumor (as defined for Stages 1, 2A, or 2B) with dissemination limited to skin, liver, and/or bone marrow; Stage 4S is limited to infants

<1 yr.

Unfortunately, most (60% to 80%) children present with Stage 3 or 4 tumors, and only 20% to 40% present with Stage 1, 2A, 2B, or 4S neuroblastomas. The staging system is of

paramount importance in determining prognosis.

Date: 2016-04-22; view: 782