Histiocytic sarcoma: New insights into FNA cytomorphology and molecular characteristics

Histiocytic sarcoma (HS) is a rare malignant neoplasm showing morphological and immunophenotypic features of mature tissue histiocytes. As HS may mimic non-Hodgkin lymphoma (NHL) pathologically, before the era of immunohistochemistry, many previously reported cases were misdiagnosed NHL. Up to date, there are only a few reports delineating the cytological features in fine-needle aspiration or bronchoalveolar lavage, but not in the effusion fluid yet. Herein, we report the case of a 61-year-old male with a mediastinal tumor presenting with malignant pleural effusion. The effusion cytology showed atypical epithelioid (histiocytoid) cells, both in loose clusters and a dispersed pattern, with scanty admixed inflammatory infiltrate. Distinct from the benign histiocytes, these tumor cells exhibited evident cytological atypia, including irregular nuclear contours, significant nuclear pleomorphism, brisk mitotic figures, and apoptotic bodies in the Papanicolaou stain. With the Liu stain, most tumor cells showed abundant blue-gray cytoplasm, some with small cytoplasmic vacuoles and formation of pseudopods. Subsequent biopsies of the tumor nodules in the right lower lung and pleura showed diffuse sheets of neoplastic cells expressing CD4, CD45, CD68, and lysozyme by immunohistochemistry, confirming the diagnosis. Usually subtyping the lymphoma in the effusion fluid is not an important issue since most patients already have previously confirmed lymphoma. In rare situation, like our patient, the disease may present initially as a malignant effusion. Immunophenotyping using cell blocks and/or excisional specimens is mandatory for a definitive diagnosis.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Cytological and Pathological Featuresmentioning

confidence: 99%

Section: Cytological and Pathological Featuresmentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Primary mediastinal histiocytic sarcoma presenting as pleural effusion

Jhuang

Chen

Chuang

2018

Imprint cytology of histiocytic sarcoma manifesting as a retroperitoneal mass: A valuable aid for frozen section diagnosis

Lee

Jeon

Lee

et al. 2020

Histiocytic sarcoma (HS) is a comparatively rare hematolymphoid neoplasm. Differential diagnosis of this entity has generally been proven to be so difficult that extensive immunohistochemical staining is required to confirm its presence. We herein present a case of HS manifesting as a retroperitoneal mass in which imprint cytology (IC) contributed to the diagnosis. A 77‐year‐old man was referred for the evaluation of a colonic tubulovillous polypoid lesion. Preoperative imaging revealed a 3 cm‐sized polypoid lesion in the transverse colon. Incidentally, a retroperitoneal mass of 8 cm in the left para‐aortic region was also detected. Diff–Quik stained IC slides were prepared as an adjunct to intraoperative pathology consultation. The smear exhibited moderate cellularity involving loosely cohesive cell clusters with intervening delicate vasculature. Most of the tumor cells consisted of large single cells with abundant eosinophilic cytoplasm that was vacuolated and foamy. The nuclei were predominantly large and eccentrically located. Mitotic figures were minimal in number and finely granular brown pigments were occasionally observed. A frozen section diagnosis was reported as a malignant neoplasm, and a histologic diagnosis of HS was confirmed by conducting a battery of immunohistochemical stains: negative for pan‐cytokeratin, EMA, CD117, HMB45, Melan A, CD30, PAX5, CD20, S‐100, and CD23 but strong positive for vimentin and CD68. This entity is rarely described in terms of cytopathologic features. This case study highlights how cytopathologists should be aware of HS as a retroperitoneal lesion and should become familiar with cytomorphologic features.

Cytopathologic findings in histiocytic sarcoma of thyroid mimicking as anaplastic carcinoma: A report of a rare case with review of literature

Gupta

Nalwa

et al. 2020

Background Histiocytic sarcoma is an extremely rare malignant hematological histiocytic neoplasm which is a diagnosis of exclusion based on its morphological and predominantly immunohistochemical criteria. Case Description and Diagnosis A 63‐year female presented with complaints of a midline neck swelling along with right sided neck swelling. On fine‐needle aspiration (FNA) from the thyroid lesion and the right cervical lymph node, the smears showed similar findings and a provisional morphological diagnosis of malignant spindle cell neoplasm was kept. On immunohistochemistry, the tumor cells showed immunoreactivity for vimentin, CD45, CD 68 and fascin and were immunonegative for thyroglobulin, S100, CD21, CD3, CD4 and other markers. Based on the immunohistochemical profile, a diagnosis of histiocytic sarcoma was established. Conclusion Histiocytic sarcoma is a rare malignant neoplasm that can be easily missed in thyroid resembling an anaplastic carcinoma.