A Rare Case of Benign Histiocytic Neoplasm of Cutaneous Rosai-Dorfman Disease: A Case Report and Literature Review.

Rosai-Dorfman disease (RDD) is a rare disorder characterized by the proliferation of histiocytes in lymph nodes. It can occur anywhere in the body but commonly involves the cervical area of the neck. Its clinical presentation varies and patients with skin manifestations may develop papules, nodules, plaques, or pustules. Histologically, it typically presents with emperipolesis, where intact lymphocytes are found within histiocytes. The definitive treatment of RDD is not well established given the rarity of the disease and indeed skin lesions can regress spontaneously. Therapeutic treatment options include cryotherapy, radiation, or topical agents such as steroids or retinoids. Here we describe the case of a 24-year-old Hispanic female who presented with skin manifestations which proved to be histologically positive for Rosai-Dorfman disease. The patient clinically improved following the administration of intralesional steroids. LEARNING POINTS: RDD is a rare self-limiting benign lymphoproliferative disorder, which can be associated with autoimmune disease, hematological malignancies, and post-infectious conditions.Skin lesions can be self-limiting in many cases of RDD.Therapeutic treatment options include cryotherapy, local radiation, and topical steroids and retinoids.

Erdheim-Chester disease presenting at the central nervous system.

Erdheim-Chester disease is a rare non-Langerhans cell histiocytosis (LCH) that affects different body systems. It was recently recognized as a neoplastic disorder after identifying an activating mutation of the MAPK pathway. Neurological presentations of ECD are rare. We present a case of a 35-year-old male who presented to the emergency department with neck pain, headache and vomiting for 2 months; MRI showed multiple heterogeneous intracranial masses. Neurosurgery performed a suboccipital craniotomy, partially resected the cerebellar mass, and placed a parietal to frontal shunt catheter. Biopsy results from the cerebellar mass demonstrated cerebellar tissue involved by a diffuse proliferation of foamy histiocytes and spindle cells admixed with prominent lymphoplasmacytic infiltrate and positive for CD68, CD163, Factor XIIIa and Fascin. PET scan showed hypermetabolic uptake within the medullary portions of the diffuse abnormal lesions of the distal femurs, tibias, and fibulas, and cardiac MRI was nonsignificant. The patient was started on vemurafenib and continued to show improvement in a 3-month outpatient follow-up.