• Disorganized and crowded sheets of pleomorphic malignant cells
• Malignant cells exhibit polygonal or spindle morphology, and occasional bizarre/anaplastic forms
• Scattered osteoclast-like multinucleated giant cells 
• Haemosiderin deposits

• Tumour fragments containing scattered pleomorphic tumour cells
• Admixed with mononuclear histiocytes and osteoclast-like multinucleated giant cells
• Frequent mitoses with atypical mitotic figures as well as some haemosiderin deposits

• MNF116 focally highlighting rare tumour cells

• CD68 highlights the osteoclast-like multinucleated giant cells and mononuclear histiocytes

Diagnosis

The overall features are those of a carcinoma, with features suggestive of an undifferentiated carcinoma with osteoclast-like giant cells (UCOGC).

Take home points

• UCOGC is a rare subtype of ductal adenocarcinoma of the pancreas, characterized histologically by variably pleomorphic tumour cells and osteoclast-like giant cells.
• It may also show necrosis, a brisk mitotic activity and other inflammatory cells such as mononuclear histiocytes and neutrophils.
• Foci of classical ductal adenocarcinoma may also be seen in some tumours.
• On immunohistochemistry, the malignant cells are variably positive for pan-cytokeratins and CD68, while the osteoclast-like giant cells are positive for CD68.
• In an adequately sampled case, the presence of classic morphologic features is sufficient for diagnosis, obviating the need for immunohistochemistry.
• Recognition of its cytologic features on smears alone is crucial to diagnosis as occasionally, there may be inadequate material for assessment in the cell block or core biopsy.

Reference: Sekulic M, Gilles S, Amin K, Stewart J. Undifferentiated (anaplastic) carcinoma with osteoclast-like giant cells of the pancreas: a series of 5 cases with clinicopathologic correlation and cytomorphologic characterization. J Am Soc Cytopathol. 2016 Nov 1;5(6):321–30.