Smears were haemorrhagic showing cells lying singly, in small nests, large clusters and in papillary fragments along with presence of vascular tissue fragments (Figure 1). Individual cells showed overlapping and were large with moderate to abundant amount of cytoplasm with many cells showing cytoplasmic vacuolisation. The nucleus was central to eccentric, round to oval with moderate degree of anisonucleosis, finely clumped chromatin and 1-2 prominent nucleoli (Figure 1, inset). There was a vague attempt to form acinar or papillaroid structures (Figure 2). However, no intranuclear inclusions, psammoma bodies or peripheral pallisading were seen in the smears examined. Few mitotic figures were seen. The presence of pleomorphic cells arranged in papillaroid and glandular patterns was suspicious of metastatic papillary adenocarcinoma. The patient was advised urgent excision. The section showed numerous intravascular papillary structures along with thrombosis at some foci (Figures 3, 4). The features were suggestive of IPEH. Immunohistochemistry was done and CD34 was found to be positive in the cells lining the papillae, confirming their endothelial origin. CD34 was also found to be positive in the adjacent fibrous stroma. A final diagnosis of IPEH was made.
Figure 4: Photomicrograph showing vascular lumen lined by endothelial cells (H&E; x100).
IPEH may be confused with a malignancy based on FNA , particularly when the lesion occurs in uncommon anatomic locations. There are only a few published reports on aspiration cytology of IPEH. The markedly atypical appearance of aspirated endothelial cells, the absence of specific features and the lack of cell block material for morphological and immunohistochemical evaluation has resulted in misdiagnosis of IPEH as a malignant neoplasm on cytology aspirates in the past[3-8].
Vascular tissue fragments should be differentiated from granulomas and granulation tissue. Vascular fragments are composed of cords and strands of spindle-shaped cells (with blunt nuclei) representing capillary vessels separated by connective tissue and are often found on a background of profuse blood. Granulomas are cohesive clusters of epithelioid cells, lymphocytes, plasma cells and giant cells. Granulation tissue is composed of cohesive clusters of fibroblasts, histiocytes, inflammatory cells and capillary vessels.
The cytological picture of IPEH is varied and thus the differential diagnosis is challenging. The cases reported by Novak et al. and Karim et al. were diagnosed as squamous cell carcinomas on cytology due to the presence of dense cytoplasm, hard cell borders, pleomorphic nuclei and prominent, multiple nucleoli[4,6]. Suh et al. and Yoo-Duk C et al. noted pleomorphic polygonal cells arranged in alveolar or glandular clusters in the smears suggesting the diagnosis of adenocarcinoma[5,9]. However, the former case was diagnosed as metastatic embryonal carcinoma in view of the patient's young age. Jain et al. noted cords and globular forms of hyaline material surrounded by plump endothelial cells and interpreted them as diagnostic of adenoid cystic carcinoma[7]. Garcia-Macias et al. reported two distinct populations of cells in IPEH[3]. One type had large nuclei, finely granular chromatin, prominent nucleoli and abundant globular cytoplasm, with occasional single cytoplasmic vacuoles. The second type of cells had spindle to oval nuclei with granular chromatin and scanty eosinophilic cytoplasm. This group identified correctly the vascular nature of the cells, but considered it to be probably malignant due to cellular atypia. Handa et al. reported a IPEH on the wrist with presence of giant cells and spindle cells on FNA smears which they interpreted as a giant cell tumor[10].
In conclusion, the cytologic features of IPEH are not specific, which often result in diagnostic challenges. However, it is important to suspect a vascular lesion when atypical cells are found on a hemorrhagic background. Furthermore, combination of cytologic features with immunocytochemistry will aid in the correct diagnosis of IPEH.
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