Abdominal Wall Yolk Sac Tumor in a Child.

Midline vascular abdominal wall lesions are likely to be mistaken for vascular malformations in young children. We report a case of large yolk sac tumor located in the anterior abdominal wall just below xiphisternum in a 20-month-old girl diagnosed by raised serum alpha fetoprotein levels and fine-needle aspiration cytology. Preoperative chemotherapy helped in reducing its size allowing wide resection and primary wound closure. This case is reported for the unusual location and role of chemotherapy in management. Copyright:

INTRODUCTION

Abdominal wall masses commonly encountered by a pediatric surgeon include hemangioma, lymphangioma, lipoma, hematoma, abscess, and neoplasms. Here, we report a rare case of yolk sac tumor (YST) presenting as a mass in the anterior abdominal wall. YST is the most common malignant germ cell tumor (GCT) in children and is mostly gonadal in location. Although 10%–15% YSTs may be extragonadal, anterior abdominal wall YST is rare and can be diagnosed only on histology.[1]

CASE REPORT

A 20-month-old girl was referred with an upper abdominal mass, noticed 3 months back with a progressive increase in size. There was no history of fever, vomiting, jaundice, abdominal pain, weight loss, irritability, or excessive crying. There was no prior history of trauma, discoloration of overlying skin, abdominal distension, or swelling elsewhere. The child appeared well nourished, and vital signs were within normal limits. There was no pallor, icterus, or lymphadenopathy. There was a 4 cm × 4 cm, nontender, firm spherical mass in the midline epigastrium with well-defined margins[ Figure 1A]. It was fixed to the underlying structures, and the overlying skin stretched with a bluish hue. Rest of the systemic examination was unremarkable. A possibility of a soft-tissue tumor or vascular malformation was considered.

Figure 1

(A) Preoperative clinical picture of abdomen showing a large lesion just below the xiphisternum. (B) Abdominal contrast-enhanced computed tomography image shows a 4.8 cm × 3.7 cm × 4.4 cm well-defined, lobulated, subcutaneous soft-tissue lesion with heterogeneous attenuation and no intra-abdominal extension. (C) Microphotograph panel (a) smear showing clusters of tumor cells with hyperchromatic nuclei and scant-to-moderate cytoplasm. (MGG, ×200) (b) Cell block showing similar tumor cells in the glandular pattern (H and E, ×200). (c and d) Positive immunocytochemical staining for SALL4 and alfa fetoprotein, respectively. (D) Postchemotherapy photograph showing the reduction in size of the tumor. (E) Intraoperative photograph shows excised tumor and midline defect with preperitoneal fat covering intra-abdominal structures

Ultrasonography showed a 4.2 cm × 4 cm echogenic lesion with few internal hyperechoic areas in the anterior abdominal wall. Its internal vascularity could not be assessed. Abdominal contrast-enhanced computed tomography (CECT) was performed [Figure 1B]. Fine-needle aspiration cytology (FNAC) of the mass revealed clusters of pleomorphic tumor cells in a myxoid background, with increased nucleo-cytoplasmic ratio and Sal-like protein 4 (SALL4) immune-stain and alpha fetoprotein (AFP) positivity, consistent with YST [Figure 1C]. Complete blood counts and renal and liver function tests were within normal limits. Serum AFP level was 2750 IU/ml (normal range: 0–5.8 IU/ml). There was no evidence of metastasis on bone scintigraphy and chest CECT.

After two cycles of neoadjuvant chemotherapy with carboplatin, etoposide, and bleomycin (JEB), the tumor size shrunk by 75%–80% and AFP level decreased to 193 IU/ml [Figure 1D]. Through an elliptical longitudinal midline incision, the mass was excised in toto with wide margins. The tumor involved the skin, subcutaneous tissue, rectus sheath, and muscle in the midline. The extraperitoneal fat was not involved [Figure 1E]. The skin and anterior rectus sheath were mobilized, and the primary closure of the wound was performed easily in layers after closing the posterior rectus sheath and bringing the rectus muscle together using 2-0 Vicryl and 4-0 Vicryl Rapide.

The postoperative course was uneventful, and she was discharged on the 2nd postoperative day on full feeds. On histopathological examination, there was no viable tumor, and the resection margins were free.

At 6-month follow-up, she is doing well with no local recurrence and a serum AFP of 9.25 IU/ml. She will be followed up with clinical examination and serum AFP levels every 3 months for the first 2 years and yearly thereafter for the next 3 years.

DISCUSSION

Pediatric GCTs are rare neoplasms, with a bimodal age distribution with peaks in under-five and pubertal age groups.[2] YSTs, also known as endodermal sinus tumors, are the most common malignant GCTs in young children. Although any organ can be involved, they are mostly gonadal in location with 10%–15% occurring in the midline structures of the mediastinum, retroperitoneum, and sacrococcygeal areas.[1]

We could find only one other case of YST of the abdominal wall in literature.[3] A small tumor located in the right hypochondrium was excised, which required a revision surgery for recurrence. Chemotherapy was not given.

GCTs arise from primordial germ cells which first appear in the wall of the yolk sac and migrate along the dorsal mesentery to the genital ridge at 4–6 weeks of embryogenesis. Extragonadal GCTs as in our case may occur due to malignant transformation of these cells retained at various sites near the midline due to migration arrest or due to stimulation of local totipotent cells.[4]

Imaging with ultrasound, CECT, or magnetic resonance imaging aid in the characterization of the mass. Serum AFP is an important diagnostic tumor biomarker as it is elevated in >90% YSTs. It correlates with disease severity and treatment response and is used for follow-up evaluation but should be interpreted in the context of age-adjusted values and serial measurements.

Although treatment for YST is surgical, outcomes used to be poor. Use of platinum-based adjuvant chemotherapy has improved survival rates to 70%–80%. Current chemotherapy protocols take into account patient age, tumor site, stage, histology, completeness of surgical resection, and treatment response monitored by tumor markers and appropriate imaging. Neoadjuvant chemotherapy is considered based on the risk group. Low-risk groups are not given chemotherapy. In our case, following excision, a mesh or abdominal flap may have been required to close the defect, especially as it was located just below xiphisternum. It shrunk considerably after neoadjuvant chemotherapy, and after excision, the wound could be closed primarily. The other role of chemotherapy is in case of a recurrence. Since the excised specimen did not show any viable tumor cells, further adjuvant chemotherapy was withheld in our patient.

Follow-up surveillance with clinical evaluation, imaging, and serum AFP levels is recommended with most relapses occurring within the first 2 years. Failure to normalize or a rising AFP level indicates incomplete resection or recurrence of the YST, even before it can be detected by imaging.[5] This case is reported for the unusual location of YST, FNAC features, and good results with a combination of chemotherapy and wide local excision.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the legal guardian has given his consent for images and other clinical information to be reported in the journal. The guardian understands that names and initials will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.