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Folliculosebaceous cystic hamartoma with a neural component: an immunohistochemical study
1Department of Dermatology, Faculty of Medicine, Toyama Medical and Pharmaceutical University, Japan.
Insights
Folliculosebaceous cystic hamartoma is a skin malformation with abnormal growth of skin components. This case highlights unusual nerve bundles lacking typical neuropeptide expression, supporting its classification as a true malformation.
Area of Science:
- Dermatopathology
- Cutaneous Oncology
- Surgical Pathology
Background:
- Folliculosebaceous cystic hamartoma (FSCH) is a rare cutaneous malformation.
- Characterized by hamartomatous proliferation of folliculosebaceous units and mesenchymal elements.
- Understanding the neuro-innervation patterns in FSCH is crucial for its classification.
Observation:
- A unique case of FSCH with prominent, thick nerve bundles in the deep dermal component.
- Immunohistochemical analysis confirmed these nerve bundles express protein gene product 9.5, a general neuronal marker.
- Absence of neuropeptide expression (CGRP, SP, VIP, NPY) within these nerve bundles was noted.
Findings:
- The aberrant nerve bundles in FSCH are neurofilament-positive but neuropeptide-negative.
- This neurochemical profile differs significantly from normal cutaneous nerves.
- The findings support FSCH as a distinct tumor-like malformation rather than a true neoplasm.
Implications:
- The distinct neuro-innervation pattern aids in the accurate diagnosis and classification of FSCH.
- Further research into the developmental pathways of FSCH neuro-innervation is warranted.
- This case contributes to the understanding of skin adnexal tumor-like malformations.
Abstract:
We present a case of follicular cystic hamartoma, a distinctive cutaneous malformation characterized by marked overgrowth of folliculosebaceous units accompanied by appreciable mesenchymal alterations, including fibroplasia, increased vascular components, and numerous adipocytes. A conspicuous feature of our case is an aggregation of thick trespassing nerve bundles in the deep portion of the neoplasm. An immunohistochemical study revealed the nerve bundles were immunoreactive for the general neuronal marker protein gene product 9.5. The nerves, however, stained negatively with antibodies against neuropeptides such as calcitonin gene-related peptide, substance P, vasoactive intestinal polypeptide, and neuropeptide Y, all of which are known to be contained in normal cutaneous nerves. The presence of these aberrant nerve bundles devoid of the normal expression of neuropeptides supports the concept that folliculosebaceous cystic hamartoma is a true, tumor-like malformation characterized by abnormal overgrowth of normal components of the skin.
