Adult onset, hypopigmented solitary mastocytoma: report of two cases.

Solitary mastocytoma is known to occur predominantly in children below 2 years of age and onset in adulthood is rare. Lesions are hyperpigmented in the majority of cases owing to the stimulation of melanin synthesis by mast cell growth factor. We hereby report two patients with adult onset solitary mastocytoma presenting as hypopigmented plaque. The first case was a 24-year-old man who presented with a plaque on the back of the neck of 5 years duration. The second case was a 30-year-old man who had a well-defined solitary, oval 3 x 2.5 cm plaque on the nape of the neck. Stroking of lesion resulted in a wheal with flare (Darier's sign) in both cases. Systemic examination was within normal limits in both cases. Histopathology revealed a dense toluidine blue-positive infiltrate of mast cells in the upper dermis in both cases.