Perineural Pattern of Aggregation of Cellular Blue Nevus: Probable Histoarchitectural Reminiscence of Histogenesis

Abstract

A striking feature of cellular blue nevus consists in the presence, in its histologic picture, of numerous hypertrophic nerves and nerve-like figures, positive for histochemical and immunohistochemical methods for nerve fibers and myelin sheaths. These findings, first described in Masson's original article and repeatedly highlighted in the past for their possible histogenetic significance, are currently considered as merely coincidental. However, the thin conventional histologic sections, catching only short tracts of the nerves, preclude a correct observation of their route and do not allow us to verify if there is an architectural relationship between them and the nevus as a whole. With this aim, we observed a few specimens of cellular blue nevus on digitally overlapped images of contiguous 25-microm-thick sections, processed with Winkelmann's technique of silver impregnation for nerve fibers, which supplied an overall, 3-dimensional view of the lesions and the nerves running through them. In these images, the lobular form of the nevus could be seen gathering around a branching hypertrophic nerve, whose stem stretched vertically from the depth to the most superficial tract of the lesion. The nevus cell aggregates invested the stem and the limbs individually, and these followed the curvilinear contour of the nevus lobules. Our images represent evidence of a preferential perineural aggregation of cellular blue nevus, at least in its lobular form. This indicates that the numerous nerves and the neuroid figures, observed in detail-but within a limited perspective- in the conventional sections, are not merely coincidental and they could indeed be a sign of neural differentiation and/or a clue to the possible neural origin of the nevus.

Perineural Infiltration: A Comprehensive Review of Diagnostic, Prognostic, and Therapeutic Implications

“…The follow-up of both patients showed no recurrence or metastasis. Castelli et al 79 described 5 cases of cellular blue nevus with PNI. All lesions demonstrated numerous nerve trunks.…”

Unraveling the Mysteries of Perineural Invasion in Benign and Malignant Conditions

“…It has several clinical variants and histological variants. A review of the literature shows rare cases of PNI in blue nevi [98,[105][106][107][108]. A case report from Min Young Lee showed a congenital plaque-type blue nevus that had PNI with no atypical markers present [109].…”

Perineural Involvement: What Does it Mean?

“…30 Five specimens, 2 with a diffuse and 3 with a lobular pattern of cellular populations, were cut into 5-mm-thick and 25-mm-thick sections stained with hematoxylin and eosin (H&E) and silver impregnation. The latter was performed to better demonstrate an architectural relationship of nerve and nevus cells routes.…”