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Cytopill is the section that provides you an insight in the cytology world and practical tips for your daily diagnostic work.

Name the cell

Name the cells is the section that will help you to easily recognise all cell types that are present in cytology samples.

Cytology case of the month

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Tumours don't read books


First of all, let me tell you that this lesion is a cutaneous histiocytoma, and the other one is a plasma cell tumour.

What are the elements that suggest a cutaneous histiocytoma in this picture? I would say mainly the lightly basophilic cytoplasm, the sometimes poorly defined cytoplasmic borders, and the mostly round but occasionally indented nuclei. We also have a mitotic figure on the top right, which is not uncommon as histiocytes may display some degree of atypia. What we are missing from the typical histiocytoma appearance are the blue background and the nucleus localisation, which should theoretically be paracentral, but in this case is mainly eccentric (as more typically seen in plasma cells)

What are the elements that suggest a cutaneous plasma cell tumour in this picture? First of all, the cytoplasm is deeply blue, with defined borders and infrequent clear perinuclear halo; nuclei are eccentric and round, as typically seen for plasma cells.

In case you are unable to provide a definitive differential diagnosis, I always recommend highlighting your main differentials (either verbally to your colleagues or written in the comment section of the cytology report). Having a histiocytoma and a plasma cell tumour (both benign lesions) in the differential list is less concerning than having a histiocytoma and a lymphoma, the latter being a malignant tumour. If you are unsure, ask for support from colleagues who are more expert than you on the subject (e.g.  external diagnostic laboratories). If the diagnosis is still uncertain, there are further investigations that can be conducted, from immunocytochemistry to histopathology, which can help to achieve a final diagnosis.

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