Introduction
Sinus histiocytosis with massive lymphadenopathy (SHML) also known as Rosai-Dorfman disease is a benign, self-limiting disease that commonly involve lymph nodes.1-6 The disease was first described by Rosai and Dorfman in 1969 7,8 and since then, there has been some many more cases reported from the available literatures.
In terms of age and sex predilection, RDD commonly affect children and young adult in their second decades life and shows slight male preponderance.9-12
RDD may show an extra nodal disease pattern (23%) particularly by having predilection to the head and neck region (75% of cases)4,13,14 and involvement of ≥1 extra nodal site has been identified in 43% of cases.13 The tendency of RDD to have simultaneous involvement of nodal and extranodal sites remains to be rare and its diagnosis may be challenging.12
SHML being a newly recognized and distinct pseudolymphomatous benign entity has distinctive microscopic features though its histocytomorphology has been documented in relatively few cases.15
SHML has several clinical features that include massive painless, bilateral, cervical lymphadenopathy which may be accompanied by leukocytosis, fever, elevated erythrocyte sedimentation rate (ESR), and hypergammaglobulinemia.1,4-6,8,10,13,16
In extra nodal cases though rare, SHML shows a distinct predilection to the head and neck region 4,14 and involved extra nodal sites include the eyes and ocular adnexa, head and neck, upper respiratory tract, skin, subcutaneous tissue, bone, skeletal muscle, central nervous system, gastrointestinal tract, salivary glands, genitourinary tract, thyroid, breast, liver, kidney, heart, uterine cervix.1,4,5,14 Misdiagnosis sometimes may be encountered in patients with massive lymphadenopathy since they may be labeled to be having lymphomas or other neoplasms depending on the affected anatomical sites such as involvement of the nose and paranasal sinuses by sinus histiocytosis.10,12,17
To date, the implicated etiological agent for RDD remains to be unknown though there are several postulated theories to explain its aetiopathogenesis. An autoimmune phenomenon (in about 10-12% of patients) has been reported to be one of the aetiology.13 Some infectious agents have also been postulated in causation such as Polyomavirus, Epstein-Barr virus, Parvovirus B19, Herpes virus type 6 and 8. 10,13Similarly, some relationship with microorganisms such as Klebsiella, Brucella and Cytomegalovirus has also been postulated in its causation10,12,13 though any attempt to isolate such organisms consistently failed.13
Other postulated mechanisms in pathogenesis of RDD include immune dysfunction or an aberrant exaggerated immune response to an infectious agent or an antigen that can cause proliferation of histiocytes and similarly, stimulation of monocytes/macrophage via macrophage colony-stimulating factor has also been postulated in causation8,12,13 thus suggesting immune system dysregulation in patients with RDD.
We report such a case of Rosai-Dorfman Disease diagnosed by FNAC and excisional biopsy with emphasis on clue to histocytopathological interpretation.