Case Number : Case 912 - 17th December Posted By: Guest

Extravasated RBC, siderophages points to Pigmented purpura , most likely lichen aurus.
Lupus, perniosis among others in the differential diagnoses.

DD of lichenoid tissue reaction. Basket weave stratum corneum points to erythema multiforme.

Acute lupus erythematosus.

A shave biopsy of a pink papule points towards a clinical suspicion of a benign skin lesion (tumor). The histopathological figures points to a Lichen planus-like keratosis (Lichenoid keratosis).

I think the DD of this LTR is wide. But if the clinical is correct (single lesion- pink papule), then we would have to call this a lichenoid keratosis.

Agree with Igor: lichen planus-like keratosis.

If the pink papule is all what the patient has, then this is lichen planus like keratosis. If it is part of a widespread papular eruption, could be acute LE or EM. More clinical details are needed...

I would add lichen nitidus to the DD

I favor erythema multiforme. There is an interface vacuolar lymphocytic infiltrate rather than a band-like one. Also, incipient subepidermal blister with sprinkling of lymphocytes, extravased erythrocytes in papillary dermis, and basket-woven stratum corneum. The very subtle ballooning of epidermis and the lack of noticeable necrotic keratinocytes are findings of an early lesion.
I'd include early Mucha-Habermann disease to the differential diagnosis, albeit this only rarely occurs in eldery.

Fixed drug eruption based on conspicious melanophages and interphase changes. By the way I am missing Dr McKee's comments..

Favor early lichenoid keratosis in context of a solitary pink papule. Agree with the above excellent differentials for interface vacuolar dermatitis. I don't see convincing evidence of a junctional melanocytic proliferation hiding within the lichenoid inflammatory process.

I think this is a lichen planus like keratosis with pseudonests.

Halo nevus , Myerson nevus ?

I like the suggesions of lichen plans-like reaction and inflammatory pseudonests (this assumes a solitary lesion of course). I routinely examine mulitple levels if I think a melanocytic lesion might be hiding but can't see it here.

Partial regression in melanoma!!!

The melanocytes show low-grade, dendritic cytology and low lentiginous density; this seems within normal range in the context of inflammation and chronic actinic exposure as evidenced by solar elastosis. Of interest, however, is the presence of sparse melanocytes spreading down the acrosyringium in the center, which raises the differential of an atypical lentiginous junctional proliferation... I would have to compare to the non-inflamed adjacent epidermis to see the 'background' melanocytic density to properly assess the significance of this finding.
Regardless, the inflammatory process does not seem to be targeting the melanocytic component, so I will stick with lichenoid keratosis, based on the above images.