Case Number : Case 1027 - 30th May Posted By: Guest

Pilomatrical carcinoma

Agree with Mona, pilomatrical carcinoma with intravascular invasion.

Pilomatrical carcinoma.

Although benign pilomatricoma may have plentiful mitosis of its basaloid cells, the images above display a tumor that shows an asymmetrical silhouette due to irregular budding growth pattern into the surrounding desmoplastic stroma and into the subcutaneous fat. Geographic necrosis and vascular invasion can also be found. Moreover, basaloid cells have rather enlarged nuclei with prominent nucleoli. So, I agree with my colleagues. This is pilomatrical carcinoma.

Pilomatrical Carcinoma

Malignant Pilomatricoma

Agree this most likely represents a pilomatrical carcinoma, possibly arising in a pre-existing pilomatricoma. The necrosis and high-grade atypia are useful features, as well described by Robledo.

To expand the differential....
1) Pilomatrical carcinoma arising in a preexistent pilomatricoma.
2) Pilomatricoma (or proliferative pilomatricoma) with FNA artefact.
Given the history of recent FNA, one may consider procedure-related necrosis/hemorrhage, and artefactual displacement of matrical cells into vessels. There is scar-like fibrosis focally. The intravascular deposit shows small, homogeneous matrical cells lacking high-grade atypia...with trapped fibrin/red cells at the periphery.

The tumour appears fairly well circumscribed at low power and extension into subcutaneous fat is not unusual for pilomatricomas. As already poinetd out, mitoses can be numerous too. Not sure if the cytology is particularly high grade.
If it hadnt been for the vascular invasion, would have struggled to call this malignant!

Giant Pilomatricoma.

I reported this as a tumour showing features of a proliferating pilomatricoma with intravascular foci of uncertain significance (spotted by Nick Turnbull our fellow). I could not see other criteria for malignancy and shared the case via powerpoint with Dmitry Kazakov who agreed with a non-commital appraisal. Obviously the patient needs to be followed up, I agree with Jim the intra-vascular tumour appeared banal. Typical mitoses are plentiful in the lesion as expected in the proliferative stage of a pilomatrixoma and I thought the lesion was well circumscribed and lacked tumour cell necrosis or any other criterion for malignancy. Dmitry Kazakov has reported a small number of otherwise benign mixed tumours with intravascular tumour at the peripheries with limited follow-up of no adverse outcome. I had reported another similar case to this around ten years ago and I am not aware the patient came to any harm (I only spotted the intra-vascular tumour reviewing the slides several years later). Eduardo Calonje reported a small series of otherwise typical hidradenoma with "benign" nodal metastases. In sum intravascular deposits of tumour unfortunately are not sufficient for a diagnosis of malignancy in isolation. Enjoy your weekends.