Case Number : Case 1941 - 07 Nov Posted By: Uma Sundram

Lymphomatoid papulosis for further studies with CD3, CD30, CD4 and CD8 immunostaining.

Yes. Agree with Anil, and thinking of a relatively new entry in LyP chapter: the type E, angiodesctructive and ulcer-emorragic lesion. I would like to know about EBV hybridization to rule out NK nasal type lymphoma.

Well, I would like to add as a ddx Langerhans cell histocytosis. Some of these cells are kidney-shaped. Immunostains are necessary. Considering the clinical picture of an isolated lesion on the forearm, this tumor can not be Lymphomatoid papulosis. It also fits with PCALCL.

Agree with Igor, due to clinical presentation I thought about PCALC, second hypothesis LCH (less likely).

Agree with all of the above. The cells have histiocytic morphology, so LCH or leukemia cutis are more likely. ALCL and other lymphomas need to be worked up if turns out to be lymphoid lineage. Other oddballs like interdigitating dendritic cell sarcoma should be kept in mind. LyP is not favored in this clinical setting. I would start with CD45, CD3, CD20, CD30, CD56, CD43, Lysozyme, CD68, CD1a, Langerin, and S100 and get at least 10 unstained sections for further investigations.

Hi All I agree with all the comments - at low power you have the classic wedge shaped area of necrosis with palisading cells. I would have considered papulo-necrotic tuberculid although this is less likely at high power! 

There are some hemocytophagic features in second picture...So I was thinking of NK nasal type Ly as differential, but agree with above comments: the cells look like reactive histiocytes. Some infection associated HLH? 

Good to exclude epitheloid sarcoma also.

Hi everyone, great comments!

The lesion was CD30+ and EBV negative. I reached out to the clinician. Turns out the patient has at least two waxing and waning papules; he was concerned about infection but thought Lyp was a good fit clinically. It can be difficult with a solitary lesion to determine pcALCL vs Lyp, and clinically there are some indeterminate cases.

Ok! So my first impression was the correct one...but I was a bit confuse about the chromatic features of lymphoid cells...hypochromatic!!! and I think in the real slide this effect isn't so impressive...

Thanks Uma for this very interesting and educative case.

Thanks for sharing this case. Type E LyP is said to be oligolesional.

Nice case!