Sinus histocytosis with massive lymphadenopathy (SHML) is a rare pathological diagnosis of Mediastinal lymphadenopathy in adults. It is a lymph nodes disease recognized in 1969 (1), which reported to be associated with different diseases and extranodal presentations (2).
A 42 year old morbidly obese, white male found to have right hilar Lymphadenopathy and bilateral pulmonary nodules, on pre-surgical evaluation for bariatric surgery; Six weeks later presented with shortness of breath, repeated chest x-ray and computerized tomography showed rapidly developing mediastinal lymphadenopathy, Positron Emission Tomography showed increased uptake in the mediastinal lymph nodes and negative uptake in the lung nodules. Patients denied any weight loss, fever, night sweat and cough. White cell count and complete metabolic profile were normal. Patient underwent mediastinoscopy with biopsies, which showed focal Sinus Histocytosis without evidence of malignancy or infection.
Radiological deferential diagnosis of rapidly progressing mediastinal lymphadenopathy includes lymphoma, metastatic cancer and infectious etiology. The histological differential diagnosis includes metastatic melanoma, metastatic carcinoma, malignant histiocytosis, Hodgkin disease, infectious processes, Langerhans cell histiocytosis, and if focal, SHML. Factors favoring SHML are large histiocytes strongly positive for S100 and negative for CD1a, and lymphophagocytosis. (3) (4) SHML commonly presents as massive, painless, bilateral lymph node enlargement in the neck with fevers. Most cases occur in the first or second decade of life and have a predilection for blacks. Rarely sites other than the lymph nodes can be involved including the central nervous system, eyes, upper respiratory tract, skin, and head and neck region. Interestingly, the spleen and bone marrow have been spared. These extranodal cases occur in up to 25% of cases. The association is dependent upon the site of the extranodal disease (5) (6). The cause is still unknown although a viral etiology is suspected. Molecular studies have found no evidence of clonal rearrangement implying that this disease is a reactive rather than neoplastic condition. SHML is reported in association with Lymphoma, chronic renal insufficiency, Human Immunodeficiency Virus, Amyloidosis, Autoimmune Hemolytic Anemia. Some cases have responded to chemotherapy but many times the disease undergoes spontaneous resolution. In others, an insidious course develops for years or decades. This is more common in the extranodal cases. Surgical indication is for life or function-threatening obstruction. Chemotherapy response rates are inferior to those seen in other hematopiotic diseases such as malignant lymphoma or Histiocytosis X. Radiotherapy responses were inferior to those expected with malignant hematopiotic neoplasms (7).
SHML is pathological diagnosis can present as rapid developing mediastinal Lymphadenopathy and positive uptake on Positron Emission Tomography.
K. Kutmah, None.