Atypical neurofibromatous neoplasms of uncertain biologic potential (ANNUBP)
Updates to Article Attributes
Atypical neurofibromas and atypical neurofibromatous neoplasms of uncertain biologic potential (collectively AN/ANNUBP) refer to neurofibromas with atypical histological features. They are considered premalignant with an increased risk of progressing to a malignantperipheral nerve sheath tumour.
Terminology
Atypical neurofibroma should be used to denote atypical histological features that do not meet the criteria for a malignantperipheral nerve sheath tumour in the setting of sporadic neurofibromas 1.
In contrast, the term ANNUBP should be used when atypical changes are encountered in the context of neurofibromatosis type 1 (NF1) 1.
Pathology
To make a diagnosis of AN/ANNUBP at least two of the following features need to be identified on histology and immunohistochemisty:
- hypercellularity
- cytological atypia
- loss of normal neurofibroma architecture
- increased mitotic count > 1 mitosis/50 HPF but less than < 3 mitoses/10 HPF of 0.51 mm in diameter and 0.2 mm2 in area)
Grading
Neurofibromas are considered WHO grade 1 tumours in the WHO classification of CNS tumours 1 whereasmalignant peripheral nerve sheath tumours (MPNST) are designated as low-grade or high-grade in the WHO classification of soft tissue and bone tumours 2.
Presumably, due to the uncertainty of the biological behaviour of AN/ANNUBP and the inconsistency in the grading nomenclature of neurofibromas and MPNST, they are not given a grade 1.
Radiographic features
The imaging characteristics of AN/ANNUBP are intermediate sharing similarities with both localised intraneural neurofibromas and malignantperipheral nerve sheath tumour, and are therefore not repeated here.
-<p><strong>Atypical neurofibromas</strong> and<strong> atypical neurofibromatous neoplasms of uncertain biologic potential </strong>(collectively AN/ANNUBP) refer to <a title="Neurofibroma" href="/articles/neurofibroma">neurofibromas</a> with atypical histological features. They are considered premalignant with an increased risk of progressing to a <a href="/articles/malignant-peripheral-nerve-sheath-tumour">malignant<strong> </strong>peripheral nerve sheath tumour</a>.</p><h4>Terminology</h4><p>Atypical neurofibroma should be used to denote atypical histological features that do not meet the criteria for a <a href="/articles/malignant-peripheral-nerve-sheath-tumour">malignant<strong> </strong>peripheral nerve sheath tumour</a> in the setting of sporadic neurofibromas <sup>1</sup>. </p><p>In contrast, the term ANNUBP should be used when atypical changes are encountered in the context of <a title="Neurofibromatosis type 1 (NF1)" href="/articles/neurofibromatosis-type-1">neurofibromatosis type 1 (NF1)</a> <sup>1</sup>. </p><h4>Pathology</h4><p>To make a diagnosis of AN/ANNUBP at least two of the following features need to be identified on histology and immunohistochemisty:</p><ul>- +<p><strong>Atypical neurofibromas</strong> and<strong> atypical neurofibromatous neoplasms of uncertain biologic potential </strong>(collectively AN/ANNUBP) refer to <a href="/articles/neurofibroma">neurofibromas</a> with atypical histological features. They are considered premalignant with an increased risk of progressing to a <a href="/articles/malignant-peripheral-nerve-sheath-tumour">malignant<strong> </strong>peripheral nerve sheath tumour</a>.</p><h4>Terminology</h4><p>Atypical neurofibroma should be used to denote atypical histological features that do not meet the criteria for a <a href="/articles/malignant-peripheral-nerve-sheath-tumour">malignant<strong> </strong>peripheral nerve sheath tumour</a> in the setting of sporadic neurofibromas <sup>1</sup>. </p><p>In contrast, the term ANNUBP should be used when atypical changes are encountered in the context of <a href="/articles/neurofibromatosis-type-1">neurofibromatosis type 1 (NF1)</a> <sup>1</sup>. </p><h4>Pathology</h4><p>To make a diagnosis of AN/ANNUBP at least two of the following features need to be identified on histology and immunohistochemisty:</p><ul>
-</ul><h5>Grading</h5><p>Neurofibromas are considered WHO grade 1 tumours in the <a title="WHO classification of CNS tumours" href="/articles/who-classification-of-cns-tumours-1">WHO classification of CNS tumours</a> <sup>1 </sup>whereas<sup> </sup>malignant peripheral nerve sheath tumours (MPNST) are designated as low-grade or high-grade in the <a title="WHO classification of soft tissue tumors" href="/articles/who-classification-of-tumors-of-soft-tissue">WHO classification of soft tissue and bone tumours</a> <sup>2</sup>. </p><p>Presumably, due to the uncertainty of the biological behaviour of AN/ANNUBP and the inconsistency in the grading nomenclature of neurofibromas and MPNST, they are not given a grade <sup>1</sup>. </p><h4>Radiographic features</h4><p>The imaging characteristics of AN/ANNUBP are intermediate sharing similarities with both <a href="/articles/neurofibroma">localised intraneural neurofibromas</a> and <a href="/articles/malignant-peripheral-nerve-sheath-tumour">malignant<strong> </strong>peripheral nerve sheath tumour</a>, and are therefore not repeated here. </p>- +</ul><h5>Grading</h5><p>Neurofibromas are considered WHO grade 1 tumours in the <a href="/articles/who-classification-of-cns-tumours-1">WHO classification of CNS tumours</a> <sup>1 </sup>whereas<sup> </sup>malignant peripheral nerve sheath tumours (MPNST) are designated as low-grade or high-grade in the <a href="/articles/who-classification-of-tumors-of-soft-tissue">WHO classification of soft tissue and bone tumours</a> <sup>2</sup>. </p><p>Presumably, due to the uncertainty of the biological behaviour of AN/ANNUBP and the inconsistency in the grading nomenclature of neurofibromas and MPNST, they are not given a grade <sup>1</sup>. </p><h4>Radiographic features</h4><p>The imaging characteristics of AN/ANNUBP are intermediate sharing similarities with both <a href="/articles/neurofibroma">localised intraneural neurofibromas</a> and <a href="/articles/malignant-peripheral-nerve-sheath-tumour">malignant<strong> </strong>peripheral nerve sheath tumour</a>, and are therefore not repeated here. </p>
References changed:
- 2. Nielsen GP, Chi P, Malignant peripheral nerve sheath tumour. In: WHO Classification of Tumours Editorial Board. Soft tissue and bone tumours. Lyon (France): International Agency for Research on Cancer; 2020. (WHO classification of tumours series, 5th ed.; vol. 3). <a href="https://publications.iarc.fr/Book-And-Report-Series/Who-Classification-Of-Tumours/Soft-Tissue-And-Bone-Tumours-2020">https://publications.iarc.fr</a>
- 2. Perry AJ, Rodriguez FO, Reuss DE, Malignant peripheral nerve sheath tumour. In: WHO Classification of Tumours Editorial Board. Soft tissue and bone tumours. Lyon (France): International Agency for Research on Cancer; 2020. (WHO classification of tumours series, 5th ed.; vol. 3). <a href="https://publications.iarc.fr/Book-And-Report-Series/Who-Classification-Of-Tumours/Soft-Tissue-And-Bone-Tumours-2020">https://publications.iarc.fr</a>