Sinus histiocytosis with massive lymphadenopathy and unusual extranodal manifestations.

Abstract We describe a predominant extranodal involvement of unusual sites by sinus histiocytosis with massive lymphadenopathy (SHML). The patient first presented at 13 years of age with bilateral parotid gland enlargement and was discovered to have a large asymptomatic left renal mass and adjacent hilar adenopathy, histologically diagnostic of SHML. Following a left nephrectomy, he remained well with persistent parotid and lacrimal gland disease and, 20 years later, plaquelike meningeal involvement mimicking meningioma en plaque developed that was associated with reactive meningeal nests within the body of the lesion. At no time during the last 20 years has there been a recurrence of significant external nodal enlargement, and biopsy specimens of neck and intrathoracic lymph nodes have been nondiagnostic of SHML.