Melanotic Progonoma: An Unusual Pathology for an Infantile Midline Scalp Mass

Melanotic progonoma is a rare neoplasm of neural crest origin with diverse clinical and radiologic differential diagnosis.The biphasic pattern of tumor cells in histopathologic examination and its immunohistochemical profile would lead to definte diagnosis when occurring in unusual locations. Case presentation: A 10-month-old infant was referred to our center due to a bulging in the scalp. On clinical examination, there was a firm, non-tender mass in the midline of the head posterior to the coronal suture with no overlying skin changes. Magnetic resonance imaging revealed a well-defined subcutaneous lesion measuring 4 × 3 × 2.5 cm without involvement of the dura mater or brainparenchyma. The lesion showed hypersignal on T1-weighted and iso- to hyposignal on T2-weighted images . The patient underwent en bloc total resection of the lesion.Histopathology showed a pigmented neoplasm, composed of clusters of tumor cells in nests and cords set in a dense collagenous stroma. Tumor cells had a biphasicproliferation pattern: some small neuro-blast cells with dense nuclei and scant cytoplasm and some large melanin-pigmented epithelial cells with large vesicularnuclei and prominent nucleoli.Immunohistochemistry was positive for synaptophysin , cytokeratin , HMB45, chromogranin , NSE and negative for LCA, S100, desminand MIC2 , all consistent with the diagnosis of melanotic progonoma.Melanotic progonoma is a rare neoplasm of neural crest origin usually affecting infants during the first year of life.It occurs most commonly in the maxilla, but mandible, skull, and brain may also be rarely involved .In MRI, the paramagnetic effect of melanin causes the tumor to show increased signal on T1-weighted and decreased signal on T2- weighted sequences .High recurrence rate and malignant transformation potential have been reported , so radical surgery and close follow-up are warranted to improve long-term outcome. Early diagnosis of the lesion on the basis of its distinctive histopathological and imaging features is mandatory as more and more cases are reported . figures will be attached in the main article

کلیدواژه ها:

skull mass ، melanotic progonoma ، infancy