Preference for the term pilomatrical carcinoma with melanocytic hyperplasia

Atypical Melanocytic Matricoma: A Case Report with Molecular Studies

ABSTRACT

Melanocytic matricoma is a rare benign pilar tumor characterized by matrical differentiation and interspersed dendritic melanocytes. It may show cellular atypia and brisk mitotic activity. Histological characterization of some lesions may be difficult. In addition, because the reported cases are few and have limited follow-up, there is insufficient experience to define outcome-based criteria for malignancy. Some cases of melanocytic matricoma with more prominent atypia have been reported as malignant, but their clinical behavior is uncertain. We present a melanocytic matricoma with interspersed benign dendritic melanocytes, but moderate basaloid atypia, focally brisk mitotic activity, and atypical mitoses. Despite the apparently good delimitation of this tumor, higher magnification revealed a slightly irregular border. However, overt malignant features such as necrosis, frank asymmetry, deep infiltration, and ulceration were not present. This tumor showed a complex aberrant genomic profile with multiple whole chromosomes or chromosomal arms, losses, and duplications. The tumor mutational burden was high. A loss-of-function alteration in CDKN2A and a loss-of-function mutation in TP53 were also present. This unexpected molecular profile contrasts with the relatively bland histology of the tumor and is in line with the difficulties in microscopic differential diagnosis between melanocytic matricoma and an indolent malignant pilomatrical tumor. We suggest that molecular studies and longer follow-up periods may help to further understand and more precisely categorize borderline pilomatrical tumors with melanocytic hyperplasia.

Melanocytic Matricoma With Atypical Histopathological Features: A Case Report of an Extremely Rare Entity and Review of the Literature

ABSTRACT

Melanocytic matricoma with atypical features is a rare, biphasic adnexal neoplasm displaying hair matrix differentiation, with only 3 reported cases worldwide. Generally, the lesion comprised a solid matrical and supramatrical cell proliferation, admixed with intermediate cell aggregates with sparse anucleated "shadow cells" and a prominent pigmented melanocytic hyperplasia. We report the case of a 78-year-old man with a slow-growing crusted lesion on the frontal left scalp, which in a matter of 1-2 months became a 0.6 cm well-defined, black purplish exophytic nodule. Histopathologically, the lesion presented a well-circumscribed border with a nodular dermal growth pattern, presenting different architectural features varying from benign pilomatricoma-like changes to atypical features such as moderate-to-high nuclear pleomorphism in both basaloid (matrical/supramatrical) and epidermal (keratinous) components. Strong nuclear and cytoplasmic positivity for β-catenin was observed in matrical cells, whereas prominent cytoplasmic membrane positivity for Melan-A in dendritic melanocytes. Owing to the evidence of atypical cytological features, we propose the "atypical/borderline" category of melanocytic matricoma as part of a possible spectrum among matrical neoplasms. Pathologists should be aware of any atypical histopathological features while reporting cases due to their potential malignant transformation.

Melanocytic Matricoma: A Potential Mimic of Malignant Melanoma

Melanocytic matricoma is a rare dermal tumor that typically presents on the sun-damaged skin of older patients. While there is controversy in the literature regarding the proper characterization of this tumor, there are certain histological and immunohistochemical features that have been described. This report presents a case of melanocytic matricoma with several unusual features that were initially feared to be malignant melanoma. Careful histologic and immunohistochemical analysis was required to rule out malignant melanoma and make the correct diagnosis. Given the rarity of melanocytic matricoma and the potential for it to mimic malignant melanoma, it is important for pathologists to keep melanocytic matricoma on the differential and be aware of the clinical, histological, and immunohistochemical features of this tumor.

Melanocytic matricoma: A report of three cases, review of the literature and suggestion of a new terminology

Melanocytic matricoma is a rare, biphasic adnexal tumor. It typical presents as a pigmented papule on the sun-damaged skin of elderly patients. Histopathology shows a dermal nodule composed of basaloid cells, ghost cells and deeply pigmented dendritic melanocytes. The basaloid cells are usually positive for β-catenin and these tumors show overlapping histopathological and molecular features with pilomatricoma. Here we review the literature on melanocytic matricoma and present three new cases. We suggest different terminology to reflect the overlapping features with pilomatricoma, that recognizes that melanocytic matricoma is likely to be a variant of pilomatricoma associated with melanocytic hyperplasia. Although melanocytic matricoma is usually considered benign, malignant transformation has been reported. This highlights the need for increased awareness of this entity. This article is protected by copyright. All rights reserved.