Interdigitating Dendritic Cell Sarcoma: Case Report and Review of Literature

Background: Interdigitating dendritic cell sarcoma (IDCS) is a very rare haematologic malignant tumour that arises from antigen-presenting cells. While it primarily affects the lymph nodes, extranodal manifestations have been observed, and there is a slight male predominance. Due to its rarity, diagnosing IDCS can be challenging, as illustrated in our case report of a 61-year-old woman. Methods: In this case presentation, the oncological management of a patient suspected of having malignant melanoma metastasis in the neck lymph nodes is discussed. This includes otorhinolaryngological examinations, fine needle aspiration biopsy, PET CT imaging, and histological analysis with immunohistochemistry. Results: The patient’s medical history included the excision of a pigmented lesion from the left ala of her nose, which was diagnosed as malignant melanoma. After surgical treatment, she experienced a tumour-free period of one year; however, during a follow-up ultrasonography three pathological lymph nodes were detected on the left side of her neck. Initially, a nodal metastasis of melanoma was suspected. Yet, fine needle aspiration cytology revealed myofibroblastic tumour invasion, and a re-biopsy showed no signs of malignancy. To further investigate, PET-CT scans were conducted, and a modified radical neck dissection was performed based on the findings. The histological analysis of the lymph nodes revealed an IDCS, a second independent tumour distinct from the initially diagnosed malignant melanoma, originating from the submandibular, upper jugular, and mid-jugular lymph nodes. Conclusions: This case highlights the diagnostic difficulties associated with IDCS. Initially, the clinical suspicion of malignant melanoma was considered, necessitating further examinations and a multidisciplinary approach to reach a final diagnosis and provide the patient with appropriate treatment.