Uma has given us a great case here with interesting Clinical Details, enjoy.

Geoff Cross - DermpathPRO Projects

The regular alternation of parakeratotic areas without a granular layer and slightly depressed orthokeratotic areas with prominent granular layer is subtle here and maybe inverted, but I think of an ILVEN

is there some acantholysis going on here...

EH and focal acantholytic dyskeratosis may be prominent features of epidermal nevi.

EPIDERMOLYTIC HYPERKERATOSIS IN INFLAMMATORY LINEAR VERRUCOUS EPIDERMAL NEVUS

Epidermal verrucous nevus with epidermolytic hyperkeratosis. 

Just to throw something else for CPC. I thought the hyperkeratosis was really massive here with quite some acanthosis so I thought of a type of palmoplantar keratoderma like striated palmoplantar keratoderma (Brunauer-Fohs-Siemens syndrome) https://www.ncbi.nlm.nih.gov/pubmed/20883380 it has mutations in desmoglein-1 so could explain also the acantholytic appearance.

thanks for sharing the info Vincenzo

Acatholytic epidermal nevus  >  striated palmoplantar keratoderma

Agree with Raul. I think this is striate palmoplantar keratoderma.  This presents as linear lesions on plams and soles. I dont think there is epidermolytic hyperkeratosis here as one should see vacuolar and granular degeneration of keratinocytes with clumping of keratin (the latter was stressed by Dr Metze in his talk on cornification disorders I attended recently). Striate palmoplantar keratoderma typically shows widening of intercellular spaces and partial dehiscence of keratinocytes, a features seen quite well in these images!

Ditto!

I agree with Raul´s comment

Raul hits the nail on the head classifying this case as a palmoplantar keratoderma. However, the patient has a linear lesion on plantar forefoot. Cases of striate palmoplantar keratoderma present with linear hyperkeratosis on palmar region, but rather nummular hyperkeratosis on the pressure points of the soles.

On the other hand, punctate palmoplantar keratoderma presents with the very same clinical characteristics described in this case history, including age of onset. Also, there is a marked hyperortokeratosis overlying an epidermal depression, the microscopic characteristics of punctate palmoplantar keratoderma.

Anyway, clinical correlation will reveal the correct diagnosis and possible associated features.

I think Raul and Arti r correct.. striate PPK fits better. 

Yes. I was off course with my diagnosis of ILVEN. Raul, Arti and Robledo gave me some tips about this dermpath topic. 

Agree with striate/circumscribed palmoplantar keratoderma.

Great ddx everyone! Clinically this was thought to be an epidermal nevus, and the findings of palmoplantar keratoderma were not present clinically. We settled on the diagnosis of acantholytic linear epidermal nevus. I think epidermolytic hyperkeratosis can be subtle, so one could also consider linear EN with EHK or ILVEN with EHK, both described in the literature (thank you Vincenzo!).

Well done Vincenzo and Mona!