Pulmonary histiocytic sarcoma mimicking pulmonary Langerhans cell histiocytosis in a young adult presenting with spontaneous pneumothorax: a potential diagnostic pitfall

Nodal histiocytic sarcoma with prominent eosinophilic infiltration: expression of eotaxin-2 on tumor cells

Background

Histiocytic sarcoma (HS) is a rare neoplasm showing morphological and immunophenotypic features of mature tissue histiocytes. We report a patient with nodal HS exhibiting prominent reactive eosinophilic infiltration.

Case presentation

A 68-year-old man presented with intermittent left lower abdominal pain and weight loss over 3 months. A computed tomography scan revealed multiple abdominal nodules. Open biopsy of the mesenteric tumors was performed for definitive diagnosis. Histologically, the tumor was comprised of a diffuse noncohesive proliferation of pleomorphic large cells, including multinucleated cells. Neoplastic cells were positive for histiocytic markers (CD68, CD163, and LIGHT) and PD-L1 but lacked markers of Langerhans cells, follicular dendritic cells, and epithelial cells. Frequent reactive inflammatory cells were intermingled in the background. Interestingly, prominent eosinophilic infiltration was also noted. Spindle neoplastic cells were prone to be present around areas with little to no eosinophilic infiltration and exhibiting fibrosis and lymphatic vessel proliferation. Conversely, polygonal neoplastic cells were prone to be present around areas with relatively large amounts of eosinophilic infiltration without fibrosis or lymphatic vessel proliferation. Immunohistochemically, the tumor cells and reactive eosinophils expressed eotaxin-2 and eotaxin-3, respectively.

Conclusion

We revealed that eotaxins induced the selective migration of eosinophils into tissues in this case. These eosinophils may affect the tumor remodeling and tumor biology characteristics of HS, such as fibrosis and lymphatic vessel proliferation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13000-020-01061-4.

Histiocytic sarcoma and underlying chronic myelomonocytic leukemia: a proposal for the developmental classification of histiocytic sarcoma

A 70-year-old male was admitted because of back pain due to peri-vertebral tumors. The histologic picture of a needle-biopsied tumor specimen showed pleomorphic large cell infiltration into the collagen fibers. On immunohistochemistry, these abnormal cells were positive for CD68, CD163 and lysozyme but negative for CD1a, 21, 30, and S100. Flow cytometric analysis also demonstrated that these cells were positive for CD13, 14, 38, 45, 56, and HLA-DR. A bone marrow aspirate showed the marked infiltration of abnormal large cells with the same surface antigens as described above. A diagnosis of HS was made. He showed monocytosis in the peripheral blood of more than 1.0 x 10(9)/L from presentation. The karyotype of bone marrow cells was 46,XY,+8. Fluorescent in situ hybridization (FISH) analysis with a probe for chromosome no. 8 showed that all these monocytes carried +8, indicating that he had another disorder of chronic myelomonocytic leukemia (CMML). FISH analysis with a probe for chromosome no. 12 demonstrated that the abnormal large cells in the bone marrow were all tetraploid, while analysis with the chromosome no. 8 probe showed more than 8 signals per cell, indicating that HS cells carried octasomy to decasomy of chromosome no. 8. These findings strongly suggest that HS in the present patient originated from underlying CMML.