Indian Journal of Pathology and Microbiology
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Year : 2022  |  Volume : 65  |  Issue : 3  |  Page : 735-736
Pilomatricoma with florid ossification: A rare feature in a common tumor

Department of Pathology, Seth G.S. Medical College and KEM Hospital, Mumbai, Maharashtra, India

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Date of Submission17-Jun-2021
Date of Acceptance14-Nov-2021
Date of Web Publication21-Jul-2022

How to cite this article:
Sathe PA, Agnihotri MA. Pilomatricoma with florid ossification: A rare feature in a common tumor. Indian J Pathol Microbiol 2022;65:735-6

How to cite this URL:
Sathe PA, Agnihotri MA. Pilomatricoma with florid ossification: A rare feature in a common tumor. Indian J Pathol Microbiol [serial online] 2022 [cited 2022 Aug 15];65:735-6. Available from: https://www.ijpmonline.org/text.asp?2022/65/3/735/351607

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A 7-year-old boy presented with a slowly growing firm painless swelling over upper back since two years. There was no significant medical or surgical history. Examination revealed a solitary, hard, ill-circumscribed, mobile nodule measuring 2 cm × 2 cm, located lateral to upper thoracic vertebrae. The swelling was superficial and the overlying skin was unremarkable. Clinical diagnosis was calcinosis cutis. The excised specimen consisted of a yellow-white irregular hard tissue measuring 2.5 cm × 1.5 cm × 1.0 cm [Figure 1]a. Skin was not identified. After decalcification, microscopic examination showed a tumor comprised of islands of shadow cells with extensive ossification and calcification [Figure 1]b & [Figure 1]c. The osteoid was focally lined by osteoblasts [Figure 1]d. Foci of non-hematopoietic marrow were evident [Figure 1]e. Surrounding stroma showed fibrosis, lymphocytic infiltrate, and multinucleated giant cells, few resembling osteoclasts [Figure 1]f. Basaloid cells were not present. Based on the above features, a diagnosis of pilomatricoma with extensive ossification was offered.
Figure 1: (a) Gross shows yellow-white irregular hard tissue. (b) Tumor composed of islands of shadow cells with extensive ossification (H and E, x100). (c) Sheets of shadow cells. (H and E, x400). (d) Transition of shadow cells to bony trabeculae with osteocytes lined by osteoblasts. (H and E, x400). (e) Bony trabeculae showing non-hematopoietic marrow. (H and E, x100). (f) Osteoclastic giant cells seen. (H and E, x100)

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Pilomatricoma or calcifying epithelioma of Malherbe, is a benign cutaneous adnexal tumor with differentiation toward hair cortex cells.[1] The most common site is the head and neck region, followed by the upper extremities, the trunk, and the lower extremities.[1] The size of the tumor ranges from 0.5 to 3 cm and it can occur at any age but is more common in children and young adults.[1]

Histopathologically, pilomatricoma is composed of uniform basaloid cells and eosinophilic keratinized anucleated cells (shadow cells).[1] Secondary reaction in the form of giant cells, calcification, chronic inflammatory cells can be seen. Dystrophic ossification is a rare occurrence and can be florid or focal.[2] Extensive osseous metaplasia, seen in the present case, is extremely rare with only 10 cases reported in English literature.[2] Although, pilomatricoma is common in children, ossification is very rare. Only one such case, also in a 7-year-old child, has been previously reported.[2] Infrequently, bony trabeculae can also show non-hematopoietic marrow or extramedullary hematopoiesis.[3] Ossification takes place in the stroma next to areas of shadow cells, probably through metaplasia of fibroblasts into osteoblasts by bone morphogenic protein (BMP-2).[3] BMP-2 has been found in shadow cells of pilomatricoma indicating that shadow cells may play a role in bone formation.[3] Pilomatricoma evolves through four distinct morphological stages: early, fully developed, early regressive, and late regressive.[4] Thus, the lesion begins as an infundibular cyst and ends up as a calcified or ossified nodule with no visible epithelial component.[4] Extensive ossification seen in late stage of neoplasm may simulate the appearance of a cutaneous osteoma if attention is not paid to the ghost cells and can lead to erroneous diagnosis. Surgical excision is the treatment of choice, as the recurrence rate is very low.[5]

The present case highlights the unusual florid ossification in pilomatricoma in a child and also emphasizes the need to look diligently for the ghost cells as they can be easily missed.

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There are no conflicts of interest.

   References Top

Anand M, Deshmukh SD, Gulati HK. Forearm pilomatricoma with extensive ossification. Int J Trichology 2011;3:133-5.  Back to cited text no. 1
Bharti S, Nalwa A, Rajendran M, Rao M, Elhence PA. Pilomatricoma with florid osseous metaplasia: A common tumor with rare histopathological finding. J Cutan Pathol 2021;48:422-4.  Back to cited text no. 2
Khuraijam B, Sobti P, Shangpliang D, Khurana N. Extramedullary haematopoiesis in a case of Pilomatricoma. J Clin Diagn Res 2016;10:ED17-8.  Back to cited text no. 3
Kaddu S, Soyer HP, Hodl S, Kerl H. Morphological stages of pilomatricoma. Am J Dermatopathol 1996;18:333-8.  Back to cited text no. 4
Ioannidis O, Stavrakis T, Cheva A, Papadimitriou N, Kotronis A, Kakoutis E, et al. Pilomatricoma of the arm with extensive ossification. Adv Med Sci 2010;55:340-2.  Back to cited text no. 5

Correspondence Address:
Mona A Agnihotri
Department of Pathology, Seth G.S. Medical College and KEM Hospital, Parel, Mumbai, Maharashtra - 400 012
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijpm.ijpm_623_21

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