Background
With less than 140 cases of interdigitating dendritic cell sarcoma (IDCS) in the published literature, any chance to learn from this rare and often lethal malignancy is worthwhile. First described in 1981, IDCS is most often found in nodal tissue but can also be found in extra-nodal sites. The most frequent site of its involvement is cervical lymph nodes. Interdigitating dendritic cells are a subset of antigen-presenting cells that are most commonly found in T-cell areas of secondary lymphoid tissue. Localised and disseminated disease are associated with a 1-year mortality rate of 21.1% and 78.9% respectively. Morphological and immunohistochemical overlap with melanoma, lymphoma, histiocytic lesions, and granulomatous inflammation make IDCS a challenge to diagnose.
Case Report
We describe a case of a 52-year-old patient with an eight-month history of a left neck lump. FNA initially suggested a diagnosis of metastatic melanoma. Staging scans confirmed localised disease to her left neck. She underwent a unilateral modified radical neck dissection and superficial parotidectomy, from which histopathological examination revealed a diagnosis of IDCS. She subsequently completed a course of adjuvant radiotherapy. The patient was reviewed at twelve months post-operatively with no clinical or radiological evidence of disease.
Conclusions
Our review of the literature following a comprehensive pooled analysis published in 2019 has emphasised the challenges associated with diagnosing and treating IDCS, its extreme rarity, and its high mortality rate. There is strong evidence for surgical excision where possible, however further data is required with respect to treatment protocols and follow-up for these patients. We hope this and other new published cases will contribute to the development of more robust treatment guidelines in the future.