True histiocytic lymphoma following acute lymphoblastic leukemia

Secondary histiocytic sarcoma may cause apparent persistence or recurrence of minimal residual disease in childhood acute lymphoblastic leukemia

Histiocytic sarcoma (HS) is a rare disease with poor prognosis which may develop subsequent to acute lymphoblastic leukemia (ALL). Here we report two children treated within the AIEOP-BFM ALL 2009 trial: one patient succumbed to fulminant hemophagocytic lymphohistiocytosis triggered by HS during ALL maintenance therapy, the other patient had a smoldering course of HS for over 2 years, and subsequently died after allogeneic stem cell transplantation. In both cases, HS and ALL were clonally related and apparent return of minimal residual disease (MRD) was detected by qPCR in bone marrow. Thus, HS should be considered in ALL when MRD appears to persist or reappear.

Primary endobronchial histiocytic sarcoma in a case of papillary carcinoma thyroid: a complex clinical scenario

Histiocytic sarcoma is a rare malignant neoplasm showing histiocytic differentiation. We document a case of a 55-year-old man presenting with cough and breathlessness following a subtotal thyroidectomy for infiltrating papillary thyroid carcinoma. An endobronchial growth was seen on endoscopy. Histopathologic examination revealed a neoplasm of histiocytic lineage with positivity for leucocyte common antigen, Vimentin, CD68, CD4, and CD45RO. To the best of our knowledge, primary endobronchial histiocytic sarcoma in association with infiltrating papillary thyroid carcinoma has not been reported in the literature so far. Our case emphasizes the importance of clinicopathologic and radiologic correlation in resolving difficult diagnostic dilemmas.

Clinicopathologic features of histiocytic lesions following ALL, with a review of the literature

We describe the clinicopathologic features of 15 patients who had histiocytic lesions that followed acute lymphoblastic leukemia (ALL). Twenty-one separate histiocytic lesions were evaluated that covered a wide spectrum, some conforming to the usual categories of juvenile xanthogranulomas (5), Langerhans' cell histiocytosis (1), Langerhans' cell sarcoma (4), Rosai-Dorfman disease (1), and histiocytic sarcoma (4). Most were atypical for the category by histology, phenotype, or abnormally high turnover rate. Seven low-grade lesions defied easy categorization and were characterized only as "atypical histiocytic lesion" following ALL. For those evaluated, the molecular signature of the prior leukemia was present in the histiocytic lesion. In 3 of 15 patients, the leukemia and histiocytic lesion shared immunoglobulin H or monoclonal TCR gene rearrangements and, in 4 of 15 patients, clonal identity was documented by fluorescence in situ hybridization. Four patients died of progressive disease, 3 of whom had histiocytic sarcoma and 1 who had an atypical lesion. One patient died of recurrent ALL. The other 10 patients are alive, 7 after recurrences and treatment with surgery and/or chemotherapy. The post-ALL lesions are more aggressive than their native counterparts, but despite the demonstration of the presence of the leukemia signature in 7 of 15 patients, the prognosis is generally favorable, except for patients with histiocytic sarcoma. It remains unclear whether the histiocytic lesions arise as a line from the original ALL or whether transdifferentiation is involved.