Vulvar Nodules: A Rare Presentation of Mastocytosis

Abstract

The hallmark of mastocytosis is a pathologic accumulation of mast cells in one or more organs. Skin is usually affected, but systemic features can occur. There is a bimodal distribution of this disease typically presenting in the first year or in third to fourth decade of life. Mastocytosis is a benign diagnosis in children, but when seen in the adult population can portend malignancy. Typically, children present with urticaria pigmentosa, however about 10-35% present with a mastocytoma. This disease is often asymptomatic, but local pruritus or systemic response to histamine can follow trauma to the area, certain medications, and heat/exercise. Treatment begins with H1 antagonists but H2 antagonist and topical corticosteroids have been used as second line alternatives. For extreme cases, epinephrine auto-injectors have been prescribed. We report a case of a 9 year old child with nodular mastocytosis of the vulva. MD is a 9 year old girl referred to the pediatric gynecology clinic from her pediatrician for labial lesions incidentally noted on exam. Her mother thought the lesions had been present for over a year. There was no itching, burning, or irritation. The masses did not change in quantity or color, but did appear more prominent over time. She and the mother confirmed no systemic complaints. Hygiene habits were appropriate for her age and she did not use any topical or systemic medications for these lesions. The patient denied abuse. She has no past medical history (specifically no history of skin conditions, asthma, or autoimmune disorders) and has never had surgery. She reported no medication, no allergies and her vaccines were up to date. She lives at home with both parents and her two siblings. On physical exam, her vitals were normal. Aside from her genital exam, she had no epidermal findings. As seen in Figure 1, she had multiple raised, bilateral, scattered papules about 2-3 mm in size. They were flesh-colored, soft, and non-fluctuant. A vulvar biopsy was performed in the operating room. Upon dermatopathologic review, exemplified by Figure 2, routine histopathology revealed a normal epidermis with an underlying dense dermal proliferation of finely granular mononuclear cells with central nuclei (A, 100X and B, 400X). An immunohistochemical stain for mast cell tryptase was positive, and confirmed a diagnosis of mastocytoma (C, 400X).Figure 2View Large Image Figure ViewerDownload Hi-res image Download (PPT) Mastocytosis is rare with a prevalence of approximately 1 in 2500 individuals. Onset of lesions occurs before that age of 2 in 55% of patients. Pediatric and adult patients may present with either cutaneous or systemic forms or both, yet children are more likely than adults to have a cutaneous disorder. Mastocytomas may occur anywhere on the body, but occur more often on the scalp, arms, and trunk. Vulvar involvement with mastocytosis is extremely rare with eight reported cases worldwide in the last 60 years. The differential diagnosis of nodular lesions of the vulva should include mastocytosis.