An Unusual Bump on the Head: Intracranial and Extracranial Cytokeratin-Positive Interstitial Reticular Cell Tumor.

Background: We describe a cytokeratin positive interstitial reticulum cell tumor (CPIRCT) as the cause of a large and defacing scalp tumor. Clinically these tumors manifest as progressive, painless swelling. Treatment usually consists of surgery with or without irradiation; chemotherapy is applied in metastatic disease.

Case Description: A patient was referred after attempted removal of a large bump on the head. The tumor was initially noted about 12 months earlier. Assuming a benign lipoma, resection without prior imaging was attempted. During surgery, the underlying bone was found to be profoundly destroyed. Cranial magnetic resonance imaging revealed a large mass with an extracranial and intracranial component. Subsequent extensive resection finally led to the diagnosis of CPIRCT.

Conclusions: Most CPIRCTs manifest as progressive palpable or visible masses. Radical excision is usually the mainstay of treatment, although there is no generally accepted treatment strategy. A needle biopsy might not be diagnostic and can complicate future curative surgery. Especially in fast-growing lesions, imaging studies should be considered before surgery. Their potential recurrence and metastatic spread render CPIRCTs an interdisciplinary challenge and highlight the need for long-term follow-up.