Rosai-Dorfman Disease (RDD), also known as sinus histiocytosis, is included in the group of rare diseases, characterized by proliferation and accumulation of histiocytes in the lymph nodes (lymphadenopathy), most often involving the cervical ganglion chains (nodal form). RDD bone involvement is rare, estimated at 10% of cases, but primary bone involvement (extranodal form), is very rare-2-8%. Usually they are solitary lesions, with multifocal primary bone manifestations being extremely rare. Histopathological analysis is of high value for a correct diagnosis. We present the case of a Caucasian woman, 42 years old, initially treated in another clinic, for an osteolytic tumor formation in the right tibial shaft. An excisional biopsy with bone trepanation was performed, the histopathological diagnosis being the chronic inflammatory tissue. The evolution was atypical, with tumor growth, extraosseous, subcutaneous. A needle biopsy was repeated in our clinic, the result being similar to the original one. Evolution of the tumor, and the radiological and imaging aspect (periosteal reaction, eroded and thin bone cortex) suggested a more aggressive disease, these being in inconsistency with the result obtained. The biopsy was repeated, as an excision type this time. The histopathological result and immunohistochemistry indicated an RDD primary bone lesion. Based on this result, and corroborated with the data from the literature, we initiated the surgical treatment, curettage and grafting with bone substitute plus safety osteosynthesis with locked plaque, the patient registering a favorable evolution. RDD primary bone lesions are in fact an atypical manifestation of a rare disease. The correct diagnosis is very difficult due to the non-specific imaging aspect. Histopathological examination errors, especially in the case of needle biopsies can lead to errors in diagnosis and treatment with negative results for the patient.
Keywords: Rosai–Dorfman disease; atypical evolution; bone involvement; difficult diagnostic; rare case.