Scalp Solitary Mastocytoma Mimicking Juvenile Xanthogranuloma

Dear Editor, A 2½-year-old male child presented with a single brownish swelling over the scalp for 4 months. Her mother claims that after using some cream, the lesion partially disappeared but returned when the cream was stopped. There was no history of trauma before the lesion. On examination, there was a well-to-ill-defined, brownish-to-skin-colored plaque of size 1.5 cm × 2 cm over the vertex area of his scalp. There was an erosion of size 0.3 cm × 0.4 cm at one side of the plaque [Figure 1]. Due to its resemblance, clinically juvenile xanthogranuloma was retained as the first differential. Our other differentials were lupus vulgaris, cylindroma, nummular eczema, and solitary mastocytoma. Human immunodeficiency virus, hepatitis B surface antigen, hepatitis C virus, and all baseline test reports were negative. There was no systemic complaint. A biopsy was done, and 3-0 suture was used for stitching the area. The histopathological report revealed keratinized stratified squamous epithelium over dermal stroma with appendages. Focal dense aggregates of mast cells having round, ovoid to elongated nuclei and few eosinophils in superficial and deep dermis, which was consistent with mastocytoma [Figures 2 and 3]. In our government setup, special stains and immunohistochemistry were not available at that time. Hence, it could not be done. We tried to elicit the Darier sign, but there was no erythema or urticated plaques. The parents were counseled regarding the disease course. Only symptomatic treatment like antihistamine and topical mometasone was given. The patient did not come for follow-up.Figure 1: Single well-to-ill-defined, brownish-to-skin-colored plaque of size 1.5 cm × 2 cm over the vertex area of the scalp, erosion of size 0.3 cm × 0.4 cm at one side of the plaque (black arrow)Figure 2: Foci of dense inflammatory cells consist of mast cells and eosinophils in superficial and deep dermis (black arrow is focused in Figure 3, stars showing other areas of aggregates) (H and E, ×100)Figure 3: Elongated mast cell-black arrow (H and E, ×400)Discussion In 1889, Nettleship was the first to report solitary cutaneous mastocytoma.[1] It is around 10%–15% of all pediatric cases of cutaneous mastocytosis.[2] Solitary cutaneous mastocytoma has been reported to develop at sites of trauma, such as a vaccination site. It is postulated that stem cell factor, nerve growth factor, and interleukin-5 are released as a result of trauma and may stimulate the proliferation of mast cells and the formation of solitary cutaneous mastocytoma.[3] Mast cell growth factors increase the number of melanocytes, which leads to hyperpigmentation.[4] The sites of involvement are the trunk, extremities, and flexural areas, followed by the head and neck. The palms and soles are usually spared.[4] In our case, the close differential was juvenile xanthogranuloma with characteristic findings, as shown in Table 1. Children presenting in the first 2 years of life experience spontaneous resolution before puberty. Rarely, progression of solitary cutaneous mastocytoma to systemic mastocytosis, mast cell leukemia, and cutaneous mast cell sarcoma has been reported.[5] Mostly, counseling and symptomatic treatment are the mainstays of management. The immunohistochemistry study and specific stains were the limitations in our instance.Table 1: Displaying some features of juvenile xanthogranuloma and solitary mastocytoma that are comparableDeclaration of consent The authors certify that they have obtained all appropriate consent forms, duly signed by the parent(s)/guardian(s) of the patient. In the form, the parent(s)/guardian(s) has/have given his/her/their consent for the images and other clinical information of their child to be reported in the journal. The parents understand that the names and initials of their child/children will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.