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|LETTER TO EDITOR
|Year : 2014 | Volume
| Issue : 6 | Page : 679-681
Yolk sac tumor of the temporal bone: An unusual presentation as hydrocephalus
Mukund Sable1, Aanchal Kakkar1, Richa Ranjan1, Ajay Garg2, Sameer Bakhshi3, Mehar Chand Sharma1
1 Department of Pathology, All India Institute of Medical Sciences, New Delhi, India
2 Department of Neuroradiology, All India Institute of Medical Sciences, New Delhi, India
3 Department of Medical Oncology, All India Institute of Medical Sciences, New Delhi, India
|Date of Submission||06-Nov-2014|
|Date of Decision||23-Nov-2014|
|Date of Acceptance||05-Dec-2014|
|Date of Web Publication||16-Jan-2015|
Mehar Chand Sharma
Department of Pathology, All India Institute of Medical Sciences, New Delhi
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Sable M, Kakkar A, Ranjan R, Garg A, Bakhshi S, Sharma MC. Yolk sac tumor of the temporal bone: An unusual presentation as hydrocephalus. Neurol India 2014;62:679-81
Yolk sac tumor (YST) occurring at extragonadal sites usually involves midline structures viz. brain, mediastinum, retroperitoneum. YST of head and neck is rare, and involvement of skull as a primary site is extremely so. 
A 3-year-old-male child presented with progressive increase in head size since birth and a right temporal swelling since 2 months. He had symptoms of raised intracranial pressure viz. irritability and decreased vision in both eyes. There was no history of fever, weight loss, or vomiting. On examination, the child had disproportionate head size (circumference 59 cm) with open and tense anterior fontenelle [Figure 1]a. A soft to firm, warm, non-tender swelling was identified over right temporal region measuring 12 cm, extending from external auditory meatus to lateral canthus of right eye. There were no sensory, motor, or cranial nerve deficits. Computed tomography showed a right temporal soft tissue space-occupying lesion with destruction of right temporal bone, extension into the cranial cavity, and evidence of hydrocephalus [Figure 1]b. Cerebrospinal fluid examination was normal. Patient underwent shunt placement, followed by excision biopsy. Microscopic examination [Figure 2] showed a cellular tumor with mixed glandular and microcystic pattern, which was infiltrating the bone. Tumor cells were cuboidal to polygonal, with eosinophillc to clear vacuolated cytoplasm and vesicular nuclei. At places, Schiller-Duval Bodies More Details were noted. An occasional mitotic figure was seen. Intracytoplasmic and extracellular eosinophilic hyaline globules were identified, which were periodic acid-Schiff (PAS)-positive and diastase-resistant. No high-grade glandular structures or solid areas suggestive of embryonal carcinoma or seminomatous differentiation, respectively, were noted. Tumor cells were immunopositive for pancytokeratin and alpha fetoprotein (AFP), and were negative for epithelial membrane antigen, desmin, myogenin, CD99, S100, GFAP, synaptophysin, and chromogranin. A diagnosis of pure YST involving right temporal bone was made. Serum alpha-fetoprotein (AFP) level was assessed and was 20,800 ng/mL. The patient was investigated to rule out a primary tumor in gonads as well as at other sites. He was started on chemotherapy with bleomycin, etoposide, and paclitaxel. After 4 months, there was marked reduction in serum AFP level as well as in tumor size. However, during the course of chemotherapy, he developed pneumothorax and died of respiratory failure.
|Figure 1: (a) Photograph of child showing right temporal swelling and disproportionate head size; (b) computed tomography showing infiltrative tumor involving temporal bone with intracranial extension|
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|Figure 2: Photomicrographs showing tumor arranged in glandular and microcystic pattern with bone destruction (a, b, c; H and E x200). At places intracytoplasmic eosinophilic globules are seen which are periodic acid-Schiff (PAS) positive and diastase resistant (d, H&E x200; e, PAS stain x200). The tumor cells show diffuse immunopositivity for á-fetoprotein and pancytokeratin but are negative for epithelial membrane antigen (EMA) (f-h x200 each)|
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YST is the commonest non-seminomatous germ cell tumor in infants and children, and most frequent site of occurrence is the gonads. Extragonadal tumors account for 20%, and location in head and neck region is rare, with brain, parapharyngeal space, nose, and maxillary sinuses being involved. ,, In intracranial location, pineal gland, and suprasellar regions are most frequently involved. There are only two case reports describing temporal bone involvement by primary YST [Table 1]. , In addition, another case of YST of external ear was reported by Stanley et al., and this patient had abnormal temporal bone development. 
|Table 1: Clinicopatholological features of published cases of temporal bone involvement by primary yolk sac tumor|
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Temporal bone involvement with a large extra- and intracranial soft tissue lesion in the pediatric age-group raises the possibilities of rhabdomyosarcoma, congenital cholesteatoma, high-grade lymphoma, meningocele, hemangioma, cystic hygroma, and germ cell tumors, including teratoma. Other close differential diagnoses for YST in temporal bone are glomus tympanicum and endolymphatic sac tumor, but these have characteristic histomorphology. Immunohistochemisty is helpful as both of these tumors are immunonegative for AFP unlike YST.
Pathogenesis of extragonadal YST is not known. A commonly accepted hypothesis is origin from primordial germ cells misplaced during migration in embryogenesis.  An alternative school of thought is that pluripotential cells which escape the influence of primary development are later on the source of germ cell tumors at ectopic sites. 
Extra-gonadal YSTs are less aggressive than gonadal tumors. Surgery followed by chemotherapy is treatment of choice regardless of disease stage. Surgical exenteration is usually not possible due to anatomic constraints. Upfront triple chemotherapy yields favorable outcome with significant remission.  However, complications of chemotherapy may lead to significant morbidity and mortality, as in the present case.
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[Figure 1], [Figure 2]
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