Asymptomatic solitary cutaneous mastocytoma: a rare presentation.

A 50-day-old female child presented with asymptomatic skin colored raised lesion on the dorsal aspect of the left wrist since the age of 10 days. The diagnosis of cutaneous mastocytoma was made based upon clinical and histopathological features.

What was known?

Majority of cases are symptomatic with positive Darier's sign.

Introduction

Urticaria pigmentosa is the most common presentation of cutaneous mastocytosis both in children and adults followed by solitary mastocytoma. Solitary mastocytoma presents with reddish brown nodular lesion up to 3-4 cm in diameter with peau d’orange appearance. Onset is generally before the age of 6 months. Urtication and blistering are seen if traumatized with blunt object and occasionally attacks of flushing can develop on stroking but solitary mastocytoma can be asymptomatic. It is commonly located on the dorsum of the hand near the wrist.

Case Report

A 50-day-old female child presented with a skin colored raised lesion on the dorsal aspect of the left wrist [Figure 1] since the age of 10 days, which gradually increased in size to attain the present size. There was no history of appearance of bullae over the lesion, wheals on other parts of the body, flushing of body, pruritus, vomiting, and diarrhea on scratching. General physical and systemic examination was normal.

Figure 1

Solitary skin colored plaque present on the extensor aspect of left wrist

On local examination, a single well-defined skin colored firm mobile plaque of 1 × 2.5 cm is present on the extensor aspect of the left wrist [Figure 1]. Surface of the plaque had peau d’orange appearance. On stroking the lesion, there was neither bulla formation on the plaque nor the appearance of wheals or flushing on other parts of the body. Routine investigations and ultrasonography of abdomen were normal.

Histopathological examination of the biopsy showed elongated rete ridges. Papillary dermis was expanded by a dense infiltrate of closely packed cuboidal cells with abundant cytoplasm and central nucleus [Figure 2]. Intracytoplasmic metachromatic granules were seen on toluidine blue staining [Figure 3a]. Immunohistochemical staining with stem cell factor receptor CD-117/c-kit was strongly positive in the cytoplasm of mast cells [Figure 3b]. A diagnosis of solitary cutaneous mastocytoma was considered.

Figure 2

Photomicrograph showing aggregates of closely packed cuboidal cells in papillary dermis (H and E, ×200)

Figure 3

(a) Photomicrograph showing intracytoplasmic metachromatic granules (Toluidine blue, ×400), (b) Photomicrograph showing strong cytoplasmic labelling with stem cell factor receptor (CD-117, ×400)

Discussion

Mastocytosis are group of disorders characterized by abnormal proliferation and accumulation of mast cells, involving the skin only (cutaneous mastocytosis) or the bone marrow and other extracutaneous organs (systemic mastocytosis). In children, skin is the most commonly involved organ.[1]

The pathogenesis of cutaneous mastocytosis is not well understood. A transient dysregulation of stem cell factor, a growth factor necessary for mast cell differentiation and growth, has been implicated as the underlying defect in cutaneous mastocytosis.[2] On an average, 10-15% of all patients with cutaneous mastocytosis have a solitary mastocytoma.[3] The majority of mastocytomas present during infancy, typically by 3 months of age, as a single indurated, red -brown macule, papule, or plaque on the trunk, extremities, head, or neck.[134] Only 10% of mastocytomas appear beyond 2 years of age.[5] The symptoms associated with solitary mastocytomas are secondary to the release of mast cell mediators (histamine). Symptoms may be localized to include pruritus or blistering of the lesion or generalized with flushing and rarely urticaria. Darier's sign may be elicited in only 50% of patients.[6]

Mast cell degranulation within solitary mastocytomas may be triggered by a variety of factors, including physical stimuli (heat, cold, friction, and pressure), emotional factors, certain medications (non-steroidal anti-inflammatory drugs, opioids, dextromethorphan, vancomycin, and general anesthetics), and radiocontrast media.[57] The diagnosis of a solitary mastocytoma is suspected by the presence of a characteristic skin lesion and confirmed by presence of mast cell clusters in biopsy and/or toluidine blue, Giemsa staining and specific mast cell marker c-kit/CD-117 staining.[8] Laboratory evaluation is rarely needed unless lesions fail to regress overtime or systemic symptoms are present. The initial laboratory evaluation includes a complete blood count with differential, comprehensive metabolic profile and a serum tryptase level in symptomatic cases and ultrasonography of the abdomen for any systemic involvement. A bone marrow biopsy is not necessary in infants and children unless extracutaneous organ involvement is suspected. The goal of management of a symptomatic solitary mastocytoma is to prevent the release of mast cell mediators and alleviate symptoms associated with mediator release, particularly pruritus. However, no intervention is required if the lesion is asymptomatic. The mainstay of therapy involves avoidance of potential triggers and oral antihistamines (H1-blockers). Other therapeutic options include psoralens UV-A, short-term application of a topical steroid under an occlusive dressing, application of calcineurin inhibitors, or targeted laser therapy.[9] Surgical excision can be curative if unresponsive to other therapies. In addition, families should be educated on the natural history of solitary mastocytomas.

Fortunately, the vast majority of children with solitary mastocytomas have a good prognosis with reduction or complete resolution of symptoms by puberty.[10] Due to spontaneous involution, solitary mastocytomas rarely remain symptomatic in older children, and only 10-15% of children have symptoms that persist into adulthood.[211]

What is new?

The asymptomatic presentation of solitary mastocytoma is rare and therefore reported.