Fine needle aspiration of Histiocytic sarcoma.

Histiocytic sarcoma is derived from histiocytes and is among the rarest of the tumors affecting the lymphoid tissue. We report a case of a histiocytic sarcoma arising from the lymph node in a 35-year-old male who came for a fine needle aspiration cytology and a subsequent biopsy was conducted and the tissue subjected to hematoxylin and eosin and immunohistochemistry staining.

Introduction

Histiocytic sarcomas are very rare tumors that affect the hematopoietic and lymphoid tissue.[12] Defined by the WHO as a malignancy with morphological and immunophenotypic features resembling mature tissue histiocytes, these tumors occur at any age and can involve multiple sites in the body.[3] Most of these neoplasms arise from the lymph nodes, the other common sites being the skin and gastrointestinal tract.[2] Involvement of multiple sites is also known. The clinical features would range from the mass, fever, weight loss, skin lesions to hepatosplenomegaly. We hereby report a case of histiocytic sarcoma in a 35-year-old male who was referred for a fine needle aspiration cytology (FNAC).

Case Report

A 35-year-old male with a swelling on the left side of the neck was referred for an FNAC. On examination the left cervical lymph nodes were enlarged and measured 3 cm × 2 cm, were discrete and mobile. There were no other swellings or any systemic symptoms. A fine needle aspiration (FNA) was performed, and large pleomorphic cells with increased nuclear cytoplasmic ratio and coarse chromatin were seen. They were present in the background of mixed inflammatory infiltrate [Figure 1a]. Emperipolesis was also seen. A presumptive diagnosis of poorly differentiated carcinoma/lymphoma was made, and a biopsy advised. The biopsy tissue was examined. The architecture of the lymph node was completely effaced and replaced by diffuse non-cohesive proliferation of large atypical cells having abundant eosinophilic cytoplasm, large nucleus, coarse chromatin and prominent nucleoli. Some multinucleated forms were also seen. Mitosis was brisk. Furthermore, admixed were lymphocytes and few eosinophils [Figure 1b]. Extensive spindling of the tumor cells was also appreciated. On immunohistochemistry (IHC) these atypical cells showed granular cytoplasmic staining for CD68 [Figure 2a]. The cells were focally positive for S100 and CD45Ro [Figure 2b]. Weak expression of CD4 was seen. The cells were negative for CD3, CD20, CD33, CD30 and vimentin. Based on the histopathological and IHC findings a diagnosis of histiocytic sarcoma was made.

Figure 1

(a) Large pleomorphic cells with increased nuclear cytoplasmic ratio and coarse chromatin seen in a background of mixed inflammatory infiltrate (Giemsa, ×400). (b) Large atypical cells having abundant eosinophilic cytoplasm, large nucleus, coarse chromatin and prominent nucleoli (H and E, ×400)

Figure 2

(a) Granular cytoplasmic staining of atypical cells with CD68 (IHC, ×100) (b) focal positivity of atypical cells with CD45 (IHC, ×100)

Discussion

Histiocytic sarcoma designated in the past as true histiocytic lymphoma is a histiocytic cell neoplasm. Very few cases have been reported in the cytology literature. Most of the previously diagnosed cases are now recognized as diffuse large B cell lymphomas (DLBCL). The term “histiocytic sarcoma” was coined in 1970 by Mathé et al.[4] One-third of the cases present in the lymph node, another one-third in the skin and the rest at extranodal sites such as intestine, bone marrow, liver, spleen, and the central nervous system.[3] Fever and weight loss is common. The age of presentation is wide with a male predilection.[13] A few cases have been described with prior mediastinal germ cell tumor and malignant teratomas.[35] The architecture of the normal organ is effaced with polymorphic tumor cells with the cells being large with increased nuclear cytoplasmic ratio, large nucleus and irregular nuclear outlines.[136] The tumor cells are positive for CD68, CD163, lysozyme, CD11c and CD14 and are negative for myeloperoxidase, CD33 and CD34.[136]

Our case was a 35-year-old male who had the sole complaint of cervical lymphadenopathy of 3 months duration. On FNA, large atypical cells with dense large nuclei were seen prompting a presumptive diagnosis of poorly differentiated carcinoma/anaplastic lymphoma. The histopathological slides of the biopsy showed effacement of lymph node architecture with large cells having pleomorphic nuclei with dense chromatin. Mitosis was brisk. A characteristic feature we noticed was spindling of tumor cells. Histiocytic sarcoma needs to be distinguished from other neoplasms like interdigitating dendritic cell tumor and DLBCL.[567] In our case, the cells were strongly positive for CD68 and focally positive for S100, CD4 and CD45Ro. IHC for CD3, CD20, CD33, CD30 and vimentin was negative. A diagnosis of interdigitating dendritic cell sarcoma was excluded as the tumor cells were not strongly positive for S100.[16] Absence of vimentin, focal S100 and strongCD68 staining also helped to exclude a diagnosis of follicular dendritic cell sarcoma.[16] Also as the tumor cells were negative for CD20 and CD30 on IHC, DLBCL could be ruled out.[16] Negativity of cytokeratin ruled out the possibility of poorly differentiated carcinoma.

Pleomorphic tumor cells with multinucleation and an inflammatory background should suggest the possibility of histiocytic sarcoma as a differential diagnosis for more common large cell non-Hodgkin's lymphomas (DLBCL and anaplastic large cell lymphoma), metastatic melanoma and metastatic undifferentiated large cell carcinoma in cytology.

As this neoplasm is rare, it requires a high degree of suspicion and it poses a diagnostic challenge and employs the use of immunohistochemical studies to establish the true histiocytic lineage to exclude other neoplasms of the lymphoid tissue.[1256]