“Pigmented pilomatricoma”: A rare histopathological variant

Neeti Goyal; Ritu Mehta; Arun Gupta; Kunal Tiwari

doi:10.4103/ijhi.IJHI_4_19

CASE REPORTS

Year : 2018 | Volume : 7 | Issue : 2 | Page : 17-19

“Pigmented pilomatricoma”: A rare histopathological variant

Neeti Goyal, Ritu Mehta, Arun Gupta, Kunal Tiwari
Department of Pathology, INHS Asvini, Mumbai, Maharashtra, India

Date of Submission	12-Apr-2019
Date of Acceptance	11-Oct-2021
Date of Web Publication	14-Mar-2022

Correspondence Address:
Neeti Goyal
Department of Pathology, INHS Asvini, Mumbai 400005, Maharashtra.
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/ijhi.IJHI_4_19

Abstract

Pilomatricoma is one of the common cutaneous benign adnexal tumors but the pigmented variant is rare among them. This is a case report of pigmented pilomatricoma in a young girl which has grown as a swelling over the supraclavicular region for 3 months and the histopathological features include basaloid cells and eosinophilic shadow cells with melanin deposition, calcification, and foreign body type giant cells.

Keywords: Adnexal, pigment, pilomatricoma, swelling

How to cite this article:
Goyal N, Mehta R, Gupta A, Tiwari K. “Pigmented pilomatricoma”: A rare histopathological variant. Int J Histopathol Interpret 2018;7:17-9

How to cite this URL:
Goyal N, Mehta R, Gupta A, Tiwari K. “Pigmented pilomatricoma”: A rare histopathological variant. Int J Histopathol Interpret [serial online] 2018 [cited 2023 May 30];7:17-9. Available from: https://www.ijhi.org/text.asp?2018/7/2/17/339627

Introduction

Pilomatricoma is a common cutaneous benign adnexal tumor; however, its variant, i.e., pigmented pilomatricoma, has been rarely documented.^[1] Its reported incidence in few of the studies is found to be less than 10%.^[1] Pigmented neoplasms with follicular differentiation are much more common than other forms of adnexal neoplasm. Though melanin-pigmented deposition has been found in many adnexal neoplasms such as Bowen’s disease, hidroacanthoma, Paget’s disease, etc., pigmented pilomatricoma is rarely reported. Proliferation of dendritic melanocytes has been observed in basaloid cells in pigmented pilomatricoma.

Case History

A 17-year-old girl presented with a gradually enlarging swelling over the left supraclavicular region of 3 months’ duration. Clinically, she was suspected with calcified tuberculoid lymph node. However, there was no history of weight loss or evening rise of temperature. There was no history of trauma, nor significant past or family history. Her blood investigation was within normal limits. Physical examination revealed a well-circumscribed, mobile, hard nodule, measuring 3 × 2 cm in size, in the supraclavicular region. Overlying skin appeared normal. No lymphadenopathy was noted. Fine needle aspiration cytology was attempted; however, it yielded only peripheral blood elements. Excision biopsy was done. Grossly it revealed a grayish brown hard mass, measuring 3 × 2 × 1.3 cm in size. The external surface was unremarkable. The cut surface was gritty and revealed grayish white areas. Microscopic examination revealed tissues lined by the stratified squamous epithelium along with underlying subepithelial tissues, which showed the presence of shadow cells, basaloid cells along with areas of abrupt keratinization as shown in [Figure 1]a. The basaloid cells had scant-to-moderate cytoplasm, round nuclei, finely stippled chromatin, and occasional cells also had prominent nucleoli. The shadow cells were eosinophilic, polygonal cells devoid of nuclei as shown. Areas of calcification and foreign body type giant cells were also noted. Melanin deposition was significantly noticed as shown in [Figure 1]b. No lymphoid cells were seen. No necrosis/mitosis noted.

Figure 1: (a) Histopathological microphotograph of pigmented pilomatricoma (H & E, ×1000) showing squamous cells, basaloid cells, and shadow cells. (b) Histopathological microphotograph of pigmented pilomatricoma (H & E, ×1000) showing melanin pigment deposition

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Based on these features, diagnosis of “pigmented pilomatricoma” was opined. The patient was regularly followed up thereafter in surgical OPD.

Discussion

Pilomatricoma, also named as Malherbe’s calcifying epithelioma, is a benign cutaneous neoplasm with differentiation toward hair matrix cells. Pilomatricomas are derived from follicular matrix keratinocytes. They show differentiation toward hair cortex and outer and inner root sheath. In a study by Watanabe et al.,^[2] comparison of pilomatricoma with normal skin using cytokeratins and involucrin showed shadow and transitional cells corresponding to the hair cortex cells, the squamoid cells to the outer root sheath, the basophilic cells adjacent to the transitional cells to the hair matrix, the basophilic cells adjacent to the stroma to the outermost cell layer of the outer root sheath. Forbis and Helwig^[3] noted trichohyaline-like granules, which were interpreted as differentiation toward inner root sheath, and were also presented in squamoid cells. Noguchi et al.^[4] found the distribution of pilomatricoma toward the density of intermediate hairs. Studies have shown that the basaloid cells can produce melanocytic trophic factors, which can lead to melanocytic hyperplasia in pilomatricoma.^[1]

Pilomatricoma can appear at any age; however, it can show bimodal age distribution with peak in first and sixth decades of life.^[5] In our study, the patient was of 17 years of age and this is in concordance with Julian and Bowers.^[5] Lesions are found commonly in the head and neck region but can be found in upper extremities also.^[3] In our study, the patient presented with swelling in the neck region which is in concordance with Forbis and Helwig.^[3] They are noted more commonly in females. Clinically, pilomatricoma usually presents as solitary, asymptomatic, firm or hard, freely mobile, subcutaneous nodule. The overlying skin surface is typically flesh-colored, but may be erythematous or bluish. Occasionally, the tumor may resemble an SCC, BCC, or malignant melanoma. Rapid enlargement of the tumor may result in internal bleeding. Subsequently, hemosiderin pigmentation can be seen.

Eight percent of the cases of pilomatricoma reported by Forbis and Helwig^[3] were pigmented. Dendritic melanocytes were also observed in pigmented pilomatricoma by Cazers et al.^[3] It is not surprising that reports of pigmented neoplasms with follicular differentiation are more frequent than other forms of adnexal neoplasms.^[6] Cazers et al. showed “pigmented calcifying epithelioma” in the previous report.^[5] The melanin pigments may be found in the stromal cells, dendritic cells, melanophages, and shadow cells. In our study, melanin pigment was found within the cytoplasm of basaloid and shadow cells. Carlson et al. recently suggested a new entity named as “malanocytic matricoma.”^[6] Matricomas are defined as neoplasms which contain all the elements of a pilomatricoma but with a different silhouette.^[6] Melanocytic matricoma showed pathology of matricoma, admixed with melanin pigments in dendritic melanocyte, epithelial cells, and melanophages. It is a distinct entity from pilomatricoma, matricoma, metrical carcinoma, proliferating pilomatricoma, trichoblastoma, and basal cell carcinoma with metrical differentiation in which pigmented variants were reported.^[6] The character of epithelial cells of pilomatricoma in hematoxylin–eosin makes themselves easy to identify and also the melanin pigment. However, silver stain can be done to demonstrate melanin, and immunohistochemical stain can be carried out in these melanocytes in the form of vimetin, S-100, and HMB45.^[6] Pilomatricoma may be pigmented, both clinically and histologically. Hair matrix differentiation of pilomatricoma may show melanocytes in addition to the keratinocytes. Hence, pigmented variant of pilomatricoma should be considered in the differential diagnosis of all pigmented lesions.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1.	Mitsuaki I, Hidetoshi O. Pigmented pilomatricoma: An unrecognized variant. Int J Clin Exp Pathol 2013;6:1890-3.
2.	Watanabe S, Wagatsuma K, Takahashi H. Immunohistochemical localization of cytokeratins and involucrin in calcifying epithelioma: Comparative studies with normal skin. Br J Dermatol 1994;131:506-13.
3.	Forbis R Jr, Helwig EB. Pilomatrixoma (calcifying epithelioma). Arch Dermatol 1961;83:606-18.
4.	Noguchi H, Hayashibara T, Ono T. A statistical study of calcifying epithelioma, focusing on the sites of origin. J Dermatol 1995;22:24-7.
5.	Julian CG, Bowers PW. A clinical review of 209 pilomatricomas. J Am Acad Dermatol 1998;39:191-5.
6.	Slominski A, Paus R, Plonka P, Chakraborty A, Maurer M, Pruski D, et al. Melanogenesis during the anagen–catagen–telogen transformation of the murine hair cycle. J Invest Dermatol 1994;102:862-9.