S100 protein expression in PKC-fused blue naevi, cellular blue naevi and PRKAR1A-inactivated pigmented epithelioid melanocytomas.

Recent data have redefined the genetic spectrum of pigmented epithelioid melanocytomas (PEMs). PEM is now defined by a secondary genetic event, a protein kinase cAMP-dependent type I regulatory subunit alpha (PRKAR1A) inactivation, that confers the specific cytomorphology of the entity, but this event can arise within a naevus with a genetic background of common, blue or Spitz type. PKC-fused melanocytic proliferations, although they can exhibit PEM-like morphological features, have now been regrouped within the blue group of tumours.

Smooth muscle hyperplasia in protein kinase C-fused blue naevi: Report of 12 cases.

Background And Aims: PKC-fused blue naevi are a recently described group of melanocytic tumours that have distinctive morphological features, including a pigmented epithelioid melanocytoma-like junctional component or a dermal biphasic architecture associating with naevocytoid nests surrounded by dendritic and spindled pigmented melanocytes (so-called 'combined common and blue naevus'). There have been reports of smooth muscle hyperplasia in a hamartoma-like pattern in cases of combined blue naevi without genetic exploration.

Materials And Methods: Herein, we describe 12 cases of protein kinase C (PKC)-fused blue tumours associated with a co-existing smooth muscle hyperplasia, identified from a total of 98 PKC-fused melanocytic tumours.