Residency Program - Case of the Month

Discussion

The pathologic findings were interpreted as consistent with dendritic cell sarcoma. These are extremely rare tumors that predominantly occur within lymph nodes and are included in the WHO classification of neoplasms having histiocytic and dendritic cell features. Furthermore, they are subdivided into interdigitating and follicular variants. Normal dendritic cells, also known as Langerhans cells, have antigen presenting functions in tissues and reside in lymph nodes after stimulation within bone marrow or mesenchymal tissues. Dendritic cell sarcomas are found in a wide age range of patients (mean age of 44) and typically presents with cervical lymphadenopathy, however, many extranodal sites of involvement have been described. The follicular dendritic variant can occur as a rare complication of hyaline vascular Castleman disease.

Dendritic cell sarcomas consist of spindle to ovoid cells that form fascicles and whorls in a nodular or sheet like pattern. The moderate amount of pale eosinophilic cytoplasm suggests a histiocytic origin. Inflammation is variable with many cases having a prominent lymphoplasmacytic or eosinophilic infiltrate. However, immunohistochemistry is needed for definitive diagnosis due to a broad morphologic differential diagnosis. Follicular dendritic cell sarcomas are positive for follicular dendritic cell markers such as CD21, CD23, or CD35 as well as CD4, CD68, and Fascin. The most common tumor with a similar appearance, especially the eosinophilic infiltrate, is Langerhans cell histiocytosis and is positive for S100, CD1a, and langerin. Other important considerations are large cell lymphomas and Hodgkin lymphoma due to the size of the cells, as well as Kimura lymphadenopathy due to the prominent eosinophilia.

References

1. Ioachim, Harry L., Howard Ratech, and Harry L. Ioachim. Ioachim's Lymph Node Pathology. Philadelphia: Lippincott, Williams & Wilkins, 2002. Print.
2. Swerdlow SH, Campo E, Harris NL, et al. (Eds). World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues, IARC Press, Lyon 2008.
3. Dalia S, Shao H, Sagatys E. Dendritic Cell and Histiocytic Neoplasms: Biology, Diagnosis, and Treatment. Cancer Control. Vol 21, No. 4. 2014. Print.