Paediatric Clear Cell Sarcoma of Scalp Masquerading as Benign Sebaceous Cyst: A Diagnostic Dilemma

Abstract

Clear Cell Sarcoma of Soft Tissue (CCSST) is a rare and aggressive tumour comprising 1% of all soft tissue sarcomas. They tend to recur locally and have a high predilection for regional, as well as, distant metastases. These tumours usually occur in a young age group; however, their presentation in childhood is extremely rare. They are also known as Malignant Melanoma (MM) of soft parts due to similar histological and Immunohistochemical (IHC) features with MM. Distinguishing between them is very difficult morphologically. Both exhibit high lymph node metastases and positive staining for S-100 protein, Melanoma antigen (Melan-A) and Human Melanoma Black-45 (HMB-45). Here, the authors reported an unusual case of an 11-year-old male child who presented with a slowly progressing scalp swelling that was misdiagnosed as a sebaceous cyst radiologically and on Fine Needle Aspiration Cytology (FNAC), which later turned out to be CCSST on histopathology. Unfortunately, the patient was lost to follow-up, but later presented with multiple cutaneous swellings, emphasising the tumour’s aggressive nature. The index case is being reported as an exception to its age of occurrence and unusual presentation that posed a diagnostic dilemma, leading to a delay in treatment. The treatment for CCSST involves wide surgical resection with negative margins, and adjuvant therapy may be considered based on resection outcomes. In conclusion, the present case underscores the diagnostic challenges posed by CCSST, particularly when it occurs in atypical age groups and locations. Timely recognition and differentiation from similar entities, such as MM, are crucial for appropriate management and improved outcomes.

Keywords

• childhood malignancy
• ewing sarcoma breakpoint region 1
• malignant melanoma